| Message ID | 1541160827-14255-1-git-send-email-fabrizio.castro@bp.renesas.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Geert Uytterhoeven |
| Headers | show |
| Series | drm/bridge/sii902x: Fix EDID readback | expand |
On 2018-11-02 13:13, Fabrizio Castro wrote: > While adding SiI9022A support to the iwg23s board, it came > up that when the HDMI transmitter is in pass through mode the > device is not compliant with the I2C specification anymore, > as it requires a far bigger tbuf, due to a delay the HDMI > transmitter is adding when relaying the STOP condition on the > monitor i2c side of things. > > When not providing an appropriate delay after the STOP condition > the i2c bus would get stuck. Also, any other traffic on the bus > while talking to the monitor may cause the transaction to fail > or even cause issues with the i2c bus as well. > > I2c-gates seemed to reach consent as a possible way to address > these issues, and as such this patch is implementing a solution > based on that. Since others are clearly relying on the current > implementation of the driver, this patch won't require any DT > changes. > > Since we don't want any interference during the DDC Bus > Request/Grant procedure and while talking to the monitor, we > have to use the adapter locking primitives rather than the > i2c-mux locking primitives. > > Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com> > --- > RFC->PATCH: > * Incorporated Linus Walleij, Peter Rosin, and Mark Brown comments > > Thank you guys > > drivers/gpu/drm/bridge/sii902x.c | 264 +++++++++++++++++++++++++++++---------- > 1 file changed, 196 insertions(+), 68 deletions(-) > > diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c > index e59a135..4f9d9c7 100644 > --- a/drivers/gpu/drm/bridge/sii902x.c > +++ b/drivers/gpu/drm/bridge/sii902x.c > @@ -1,4 +1,6 @@ > /* > + * Copyright (C) 2018 Renesas Electronics > + * > * Copyright (C) 2016 Atmel > * Bo Shen <voice.shen@atmel.com> > * > @@ -21,6 +23,7 @@ > */ > > #include <linux/gpio/consumer.h> > +#include <linux/i2c-mux.h> > #include <linux/i2c.h> > #include <linux/module.h> > #include <linux/regmap.h> > @@ -86,8 +89,68 @@ struct sii902x { > struct drm_bridge bridge; > struct drm_connector connector; > struct gpio_desc *reset_gpio; > + struct i2c_mux_core *i2cmux; > }; > > +static int sii902x_read_unlocked(struct i2c_client *i2c, u8 reg, u8 *val) > +{ > + struct i2c_msg xfer[] = { > + { > + .addr = i2c->addr, > + .flags = 0, > + .len = 1, > + .buf = ®, > + }, { > + .addr = i2c->addr, > + .flags = I2C_M_RD, > + .len = 1, > + .buf = val, > + } > + }; > + unsigned char xfers = ARRAY_SIZE(xfer); > + int ret, retries = 5; > + > + do { > + ret = __i2c_transfer(i2c->adapter, xfer, xfers); > + if (ret < 0) > + return ret; > + } while (ret != xfers && --retries); > + return ret == xfers ? 0 : -1; > +} > + > +static int sii902x_write_unlocked(struct i2c_client *i2c, u8 reg, u8 val) > +{ > + u8 data[2] = {reg, val}; > + struct i2c_msg xfer = { > + .addr = i2c->addr, > + .flags = 0, > + .len = sizeof(data), > + .buf = data, > + }; > + int ret, retries = 5; > + > + do { > + ret = __i2c_transfer(i2c->adapter, &xfer, 1); > + if (ret < 0) > + return ret; > + } while (!ret && --retries); > + return !ret ? -1 : 0; > +} > + > +static int sii902x_update_bits_unlocked(struct i2c_client *i2c, u8 reg, u8 mask, > + u8 val) > +{ > + int ret; > + u8 status; > + > + ret = sii902x_read_unlocked(i2c, reg, &status); > + if (ret) > + return ret; > + status &= ~mask; > + status |= val & mask; > + return sii902x_write_unlocked(i2c, reg, status); > +} > + > static inline struct sii902x *bridge_to_sii902x(struct drm_bridge *bridge) > { > return container_of(bridge, struct sii902x, bridge); > @@ -135,41 +198,11 @@ static const struct drm_connector_funcs sii902x_connector_funcs = { > static int sii902x_get_modes(struct drm_connector *connector) > { > struct sii902x *sii902x = connector_to_sii902x(connector); > - struct regmap *regmap = sii902x->regmap; > u32 bus_format = MEDIA_BUS_FMT_RGB888_1X24; > - struct device *dev = &sii902x->i2c->dev; > - unsigned long timeout; > - unsigned int retries; > - unsigned int status; > struct edid *edid; > - int num = 0; > - int ret; > - > - ret = regmap_update_bits(regmap, SII902X_SYS_CTRL_DATA, > - SII902X_SYS_CTRL_DDC_BUS_REQ, > - SII902X_SYS_CTRL_DDC_BUS_REQ); > - if (ret) > - return ret; > - > - timeout = jiffies + > - msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); > - do { > - ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, &status); > - if (ret) > - return ret; > - } while (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD) && > - time_before(jiffies, timeout)); > - > - if (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD)) { > - dev_err(dev, "failed to acquire the i2c bus\n"); > - return -ETIMEDOUT; > - } > - > - ret = regmap_write(regmap, SII902X_SYS_CTRL_DATA, status); > - if (ret) > - return ret; > + int num = 0, ret; > > - edid = drm_get_edid(connector, sii902x->i2c->adapter); > + edid = drm_get_edid(connector, sii902x->i2cmux->adapter[0]); > drm_connector_update_edid_property(connector, edid); > if (edid) { > num = drm_add_edid_modes(connector, edid); > @@ -181,42 +214,6 @@ static int sii902x_get_modes(struct drm_connector *connector) > if (ret) > return ret; > > - /* > - * Sometimes the I2C bus can stall after failure to use the > - * EDID channel. Retry a few times to see if things clear > - * up, else continue anyway. > - */ > - retries = 5; > - do { > - ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, > - &status); > - retries--; > - } while (ret && retries); > - if (ret) > - dev_err(dev, "failed to read status (%d)\n", ret); > - > - ret = regmap_update_bits(regmap, SII902X_SYS_CTRL_DATA, > - SII902X_SYS_CTRL_DDC_BUS_REQ | > - SII902X_SYS_CTRL_DDC_BUS_GRTD, 0); > - if (ret) > - return ret; > - > - timeout = jiffies + > - msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); > - do { > - ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, &status); > - if (ret) > - return ret; > - } while (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | > - SII902X_SYS_CTRL_DDC_BUS_GRTD) && > - time_before(jiffies, timeout)); > - > - if (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | > - SII902X_SYS_CTRL_DDC_BUS_GRTD)) { > - dev_err(dev, "failed to release the i2c bus\n"); > - return -ETIMEDOUT; > - } > - > return num; > } > > @@ -366,6 +363,112 @@ static irqreturn_t sii902x_interrupt(int irq, void *data) > return IRQ_HANDLED; > } > > +/* > + * The purpose of sii902x_i2c_bypass_select is to enable the pass through > + * mode of the HDMI transmitter. Do not use regmap from within this function, > + * only use sii902x_*_unlocked functions to read/modify/write registers. > + * We are holding the parent adapter lock here, keep this in mind before > + * adding more i2c transactions. > + */ > +static int sii902x_i2c_bypass_select(struct i2c_mux_core *mux, u32 chan_id) > +{ > + struct sii902x *sii902x = i2c_mux_priv(mux); > + struct device *dev = &sii902x->i2c->dev; > + unsigned long timeout; > + u8 status; > + int ret; > + > + ret = sii902x_update_bits_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + SII902X_SYS_CTRL_DDC_BUS_REQ, > + SII902X_SYS_CTRL_DDC_BUS_REQ); Here (and also in sii902x_i2c_bypass_deselect) you do a rmw access to the SII902X_SYS_CTRL_DATA register without coordinating with regmap. Regmap is also doing rmw accesses to that register in other parts of the driver. I think you need to either add comment as to why that is safe (maybe other things make it impossible for the two rmw accesses to cross?), or add the missing coordination. > + > + timeout = jiffies + > + msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); > + do { > + ret = sii902x_read_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + &status); > + if (ret) > + return ret; > + } while (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD) && > + time_before(jiffies, timeout)); > + > + if (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD)) { > + dev_err(dev, "Failed to acquire the i2c bus\n"); > + return -ETIMEDOUT; > + } > + > + ret = sii902x_write_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + status); > + if (ret) > + return ret; > + return 0; > +} > + > +/* > + * The purpose of sii902x_i2c_bypass_deselect is to disable the pass through > + * mode of the HDMI transmitter. Do not use regmap from within this function, > + * only use sii902x_*_unlocked functions to read/modify/write registers. > + * We are holding the parent adapter lock here, keep this in mind before > + * adding more i2c transactions. > + */ > +static int sii902x_i2c_bypass_deselect(struct i2c_mux_core *mux, u32 chan_id) > +{ > + struct sii902x *sii902x = i2c_mux_priv(mux); > + struct device *dev = &sii902x->i2c->dev; > + unsigned long timeout; > + unsigned int retries; > + u8 status; > + int ret; > + > + /* > + * When the HDMI transmitter is in pass through mode, we need an > + * (undocumented) additional delay between STOP and START conditions > + * to guarantee the bus won't get stuck. > + */ > + udelay(30); > + > + /* > + * Sometimes the I2C bus can stall after failure to use the > + * EDID channel. Retry a few times to see if things clear > + * up, else continue anyway. > + */ > + retries = 5; > + do { > + ret = sii902x_read_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + &status); > + retries--; > + } while (ret && retries); > + if (ret) { > + dev_err(dev, "failed to read status (%d)\n", ret); > + return ret; > + } > + > + ret = sii902x_update_bits_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + SII902X_SYS_CTRL_DDC_BUS_REQ | > + SII902X_SYS_CTRL_DDC_BUS_GRTD, 0); > + if (ret) > + return ret; > + > + timeout = jiffies + > + msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); > + do { > + ret = sii902x_read_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + &status); > + if (ret) > + return ret; > + } while (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | > + SII902X_SYS_CTRL_DDC_BUS_GRTD) && > + time_before(jiffies, timeout)); > + > + if (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | > + SII902X_SYS_CTRL_DDC_BUS_GRTD)) { > + dev_err(dev, "failed to release the i2c bus\n"); > + return -ETIMEDOUT; > + } > + > + return 0; > +} > + > static int sii902x_probe(struct i2c_client *client, > const struct i2c_device_id *id) > { > @@ -375,6 +478,12 @@ static int sii902x_probe(struct i2c_client *client, > u8 chipid[4]; > int ret; > > + ret = i2c_check_functionality(client->adapter, I2C_FUNC_I2C); > + if (!ret) { > + dev_err(dev, "I2C adapter not suitable\n"); > + return -EIO; > + } > + > sii902x = devm_kzalloc(dev, sizeof(*sii902x), GFP_KERNEL); > if (!sii902x) > return -ENOMEM; > @@ -433,6 +542,22 @@ static int sii902x_probe(struct i2c_client *client, > > i2c_set_clientdata(client, sii902x); > > + sii902x->i2cmux = i2c_mux_alloc(client->adapter, dev, > + 1, 0, I2C_MUX_GATE, > + sii902x_i2c_bypass_select, > + sii902x_i2c_bypass_deselect); > + if (!sii902x->i2cmux) { > + dev_err(dev, "failed to allocate I2C mux\n"); > + return -ENOMEM; > + } > + > + sii902x->i2cmux->priv = sii902x; > + ret = i2c_mux_add_adapter(sii902x->i2cmux, 0, 0, 0); > + if (ret) { > + dev_err(dev, "Couldn't add i2c mux adapter\n"); > + return ret; > + } > + > return 0; > } > > @@ -441,6 +566,9 @@ static int sii902x_remove(struct i2c_client *client) > { > struct sii902x *sii902x = i2c_get_clientdata(client); > > + if (sii902x->i2cmux) > + i2c_mux_del_adapters(sii902x->i2cmux); > + > drm_bridge_remove(&sii902x->bridge); > > return 0; >
Hello Peter, Thank you for your feedback! > > +static int sii902x_i2c_bypass_select(struct i2c_mux_core *mux, u32 chan_id) > > +{ > > +struct sii902x *sii902x = i2c_mux_priv(mux); > > +struct device *dev = &sii902x->i2c->dev; > > +unsigned long timeout; > > +u8 status; > > +int ret; > > + > > +ret = sii902x_update_bits_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > > + SII902X_SYS_CTRL_DDC_BUS_REQ, > > + SII902X_SYS_CTRL_DDC_BUS_REQ); > > Here (and also in sii902x_i2c_bypass_deselect) you do a rmw access to the > SII902X_SYS_CTRL_DATA register without coordinating with regmap. Regmap is > also doing rmw accesses to that register in other parts of the driver. I > think you need to either add comment as to why that is safe (maybe other > things make it impossible for the two rmw accesses to cross?), or add the > missing coordination. > The other two places where SII902X_SYS_CTRL_DATA is being handled are sii902x_bridge_disable and sii902x_bridge_enable, I didn’t think there is any chance of the modes being probed while the bridge gets enabled/disabled, but now that you make me think about it user space may trigger the readback of the EDID at the most inconvenient times. Anyway, this is a good point, and since I don't think I am supposed to access regmap's lock from outside the APIs, I could switch to the unlocked version of update_bits from within sii902x_bridge_disable and sii902x_bridge_enable, and manually grab the i2c adapter lock, what do you think? Fab Renesas Electronics Europe Ltd, Dukes Meadow, Millboard Road, Bourne End, Buckinghamshire, SL8 5FH, UK. Registered in England & Wales under Registered No. 04586709.
> > Here (and also in sii902x_i2c_bypass_deselect) you do a rmw access to the > > SII902X_SYS_CTRL_DATA register without coordinating with regmap. Regmap is > > also doing rmw accesses to that register in other parts of the driver. I > > think you need to either add comment as to why that is safe (maybe other > > things make it impossible for the two rmw accesses to cross?), or add the > > missing coordination. > > > > The other two places where SII902X_SYS_CTRL_DATA is being handled are > sii902x_bridge_disable and sii902x_bridge_enable, I didn’t think there is > any chance of the modes being probed while the bridge gets enabled/disabled, > but now that you make me think about it user space may trigger the readback > of the EDID at the most inconvenient times. Anyway, this is a good point, and > since I don't think I am supposed to access regmap's lock from outside the APIs, > I could switch to the unlocked version of update_bits from within sii902x_bridge_disable > and sii902x_bridge_enable, and manually grab the i2c adapter lock, what do you think? > The bridge enable/disable callbacks deal with different bits of register SII902X_SYS_CTRL_DATA, and the value of register SII902X_SYS_CTRL_DATA after sii902x_i2c_bypass_deselect is the same as when sii902x_i2c_bypass_select gets triggered so basically even if we managed to get in the way of the regmap rmw (in the sense that for example sii902x_bridge_enable reads SII902X_SYS_CTRL_DATA and then we call into sii902x_i2c_bypass_select) by the time regmap_update_bits can perform the write operation the value of register SII902X_SYS_CTRL_DATA is the same as the one read by regmap, as "select xfer deselect" won't alter the final value of SII902X_SYS_CTRL_DATA and nobody can get in between. What do you think I should do? Do you think I can leave this alone and maybe add some comments or do you think I should explicitly protect access to SII902X_SYS_CTRL_DATA? Thanks, Fab Renesas Electronics Europe Ltd, Dukes Meadow, Millboard Road, Bourne End, Buckinghamshire, SL8 5FH, UK. Registered in England & Wales under Registered No. 04586709.
On 2018-11-02 17:16, Fabrizio Castro wrote: >>> Here (and also in sii902x_i2c_bypass_deselect) you do a rmw access to the >>> SII902X_SYS_CTRL_DATA register without coordinating with regmap. Regmap is >>> also doing rmw accesses to that register in other parts of the driver. I >>> think you need to either add comment as to why that is safe (maybe other >>> things make it impossible for the two rmw accesses to cross?), or add the >>> missing coordination. >>> >> >> The other two places where SII902X_SYS_CTRL_DATA is being handled are >> sii902x_bridge_disable and sii902x_bridge_enable, I didn’t think there is >> any chance of the modes being probed while the bridge gets enabled/disabled, >> but now that you make me think about it user space may trigger the readback >> of the EDID at the most inconvenient times. Anyway, this is a good point, and >> since I don't think I am supposed to access regmap's lock from outside the APIs, >> I could switch to the unlocked version of update_bits from within sii902x_bridge_disable >> and sii902x_bridge_enable, and manually grab the i2c adapter lock, what do you think? >> > > The bridge enable/disable callbacks deal with different bits of register > SII902X_SYS_CTRL_DATA, and the value of register SII902X_SYS_CTRL_DATA after > sii902x_i2c_bypass_deselect is the same as when sii902x_i2c_bypass_select gets triggered > so basically even if we managed to get in the way of the regmap rmw (in the sense that > for example sii902x_bridge_enable reads SII902X_SYS_CTRL_DATA and then we call > into sii902x_i2c_bypass_select) by the time regmap_update_bits can perform the > write operation the value of register SII902X_SYS_CTRL_DATA is the same as the one > read by regmap, as "select xfer deselect" won't alter the final value of SII902X_SYS_CTRL_DATA > and nobody can get in between. > What do you think I should do? Do you think I can leave this alone and maybe add some > comments or do you think I should explicitly protect access to SII902X_SYS_CTRL_DATA? If the things you write about the bits are true (haven't looked closely), I wouldn't add any regmap coordination. But if I was the maintainer, I'd like a comment about this so that the next contributor has a better chance to understand the subtlety. But I'm not the maintainer, so this is not my call, but by adding the comment you also clarify the situation for the maintainer, which is something that is likely to be appreciated. Cheers, Peter
On 2018-11-02 13:13, Fabrizio Castro wrote: > While adding SiI9022A support to the iwg23s board, it came > up that when the HDMI transmitter is in pass through mode the > device is not compliant with the I2C specification anymore, > as it requires a far bigger tbuf, due to a delay the HDMI > transmitter is adding when relaying the STOP condition on the > monitor i2c side of things. > > When not providing an appropriate delay after the STOP condition > the i2c bus would get stuck. Also, any other traffic on the bus > while talking to the monitor may cause the transaction to fail > or even cause issues with the i2c bus as well. > > I2c-gates seemed to reach consent as a possible way to address > these issues, and as such this patch is implementing a solution > based on that. Since others are clearly relying on the current > implementation of the driver, this patch won't require any DT > changes. > > Since we don't want any interference during the DDC Bus > Request/Grant procedure and while talking to the monitor, we > have to use the adapter locking primitives rather than the > i2c-mux locking primitives. > > Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com> > --- > RFC->PATCH: > * Incorporated Linus Walleij, Peter Rosin, and Mark Brown comments > > Thank you guys > > drivers/gpu/drm/bridge/sii902x.c | 264 +++++++++++++++++++++++++++++---------- > 1 file changed, 196 insertions(+), 68 deletions(-) > > diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c > index e59a135..4f9d9c7 100644 > --- a/drivers/gpu/drm/bridge/sii902x.c > +++ b/drivers/gpu/drm/bridge/sii902x.c > @@ -1,4 +1,6 @@ > /* > + * Copyright (C) 2018 Renesas Electronics > + * > * Copyright (C) 2016 Atmel > * Bo Shen <voice.shen@atmel.com> > * > @@ -21,6 +23,7 @@ > */ > > #include <linux/gpio/consumer.h> > +#include <linux/i2c-mux.h> > #include <linux/i2c.h> > #include <linux/module.h> > #include <linux/regmap.h> > @@ -86,8 +89,68 @@ struct sii902x { > struct drm_bridge bridge; > struct drm_connector connector; > struct gpio_desc *reset_gpio; > + struct i2c_mux_core *i2cmux; > }; > > +static int sii902x_read_unlocked(struct i2c_client *i2c, u8 reg, u8 *val) > +{ > + struct i2c_msg xfer[] = { > + { > + .addr = i2c->addr, > + .flags = 0, > + .len = 1, > + .buf = ®, > + }, { > + .addr = i2c->addr, > + .flags = I2C_M_RD, > + .len = 1, > + .buf = val, > + } > + }; > + unsigned char xfers = ARRAY_SIZE(xfer); > + int ret, retries = 5; > + > + do { > + ret = __i2c_transfer(i2c->adapter, xfer, xfers); > + if (ret < 0) > + return ret; > + } while (ret != xfers && --retries); > + return ret == xfers ? 0 : -1; New in 4.19 __i2c_smbus_xfer, and I think it helps here? (untested code) union i2c_smbus_data data; int ret; ret = __i2c_smbus_xfer(i2c->adapter, i2c->addr, i2c->flags, I2C_SMBUS_READ, reg, I2C_SMBUS_BYTE_DATA, &data); if (ret < 0) return ret; *val = data.byte; return 0; > +} > + > +static int sii902x_write_unlocked(struct i2c_client *i2c, u8 reg, u8 val) > +{ > + u8 data[2] = {reg, val}; > + struct i2c_msg xfer = { > + .addr = i2c->addr, > + .flags = 0, > + .len = sizeof(data), > + .buf = data, > + }; > + int ret, retries = 5; > + > + do { > + ret = __i2c_transfer(i2c->adapter, &xfer, 1); > + if (ret < 0) > + return ret; > + } while (!ret && --retries); > + return !ret ? -1 : 0; union i2c_smbus_data data; data.byte = val; return __i2c_smbus_xfer(i2c->adapter, i2c->addr, i2c->flags, I2C_SMBUS_WRITE, reg, I2C_SMBUS_BYTE_DATA, &data); > +} > + > +static int sii902x_update_bits_unlocked(struct i2c_client *i2c, u8 reg, u8 mask, > + u8 val) > +{ > + int ret; > + u8 status; > + > + ret = sii902x_read_unlocked(i2c, reg, &status); > + if (ret) > + return ret; > + status &= ~mask; > + status |= val & mask; > + return sii902x_write_unlocked(i2c, reg, status); > +} > + > static inline struct sii902x *bridge_to_sii902x(struct drm_bridge *bridge) > { > return container_of(bridge, struct sii902x, bridge); > @@ -135,41 +198,11 @@ static const struct drm_connector_funcs sii902x_connector_funcs = { > static int sii902x_get_modes(struct drm_connector *connector) > { > struct sii902x *sii902x = connector_to_sii902x(connector); > - struct regmap *regmap = sii902x->regmap; > u32 bus_format = MEDIA_BUS_FMT_RGB888_1X24; > - struct device *dev = &sii902x->i2c->dev; > - unsigned long timeout; > - unsigned int retries; > - unsigned int status; > struct edid *edid; > - int num = 0; > - int ret; > - > - ret = regmap_update_bits(regmap, SII902X_SYS_CTRL_DATA, > - SII902X_SYS_CTRL_DDC_BUS_REQ, > - SII902X_SYS_CTRL_DDC_BUS_REQ); > - if (ret) > - return ret; > - > - timeout = jiffies + > - msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); > - do { > - ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, &status); > - if (ret) > - return ret; > - } while (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD) && > - time_before(jiffies, timeout)); > - > - if (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD)) { > - dev_err(dev, "failed to acquire the i2c bus\n"); > - return -ETIMEDOUT; > - } > - > - ret = regmap_write(regmap, SII902X_SYS_CTRL_DATA, status); > - if (ret) > - return ret; > + int num = 0, ret; > > - edid = drm_get_edid(connector, sii902x->i2c->adapter); > + edid = drm_get_edid(connector, sii902x->i2cmux->adapter[0]); > drm_connector_update_edid_property(connector, edid); > if (edid) { > num = drm_add_edid_modes(connector, edid); > @@ -181,42 +214,6 @@ static int sii902x_get_modes(struct drm_connector *connector) > if (ret) > return ret; > > - /* > - * Sometimes the I2C bus can stall after failure to use the > - * EDID channel. Retry a few times to see if things clear > - * up, else continue anyway. > - */ > - retries = 5; > - do { > - ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, > - &status); > - retries--; > - } while (ret && retries); > - if (ret) > - dev_err(dev, "failed to read status (%d)\n", ret); > - > - ret = regmap_update_bits(regmap, SII902X_SYS_CTRL_DATA, > - SII902X_SYS_CTRL_DDC_BUS_REQ | > - SII902X_SYS_CTRL_DDC_BUS_GRTD, 0); > - if (ret) > - return ret; > - > - timeout = jiffies + > - msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); > - do { > - ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, &status); > - if (ret) > - return ret; > - } while (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | > - SII902X_SYS_CTRL_DDC_BUS_GRTD) && > - time_before(jiffies, timeout)); > - > - if (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | > - SII902X_SYS_CTRL_DDC_BUS_GRTD)) { > - dev_err(dev, "failed to release the i2c bus\n"); > - return -ETIMEDOUT; > - } > - > return num; > } > > @@ -366,6 +363,112 @@ static irqreturn_t sii902x_interrupt(int irq, void *data) > return IRQ_HANDLED; > } > > +/* > + * The purpose of sii902x_i2c_bypass_select is to enable the pass through > + * mode of the HDMI transmitter. Do not use regmap from within this function, > + * only use sii902x_*_unlocked functions to read/modify/write registers. > + * We are holding the parent adapter lock here, keep this in mind before > + * adding more i2c transactions. > + */ > +static int sii902x_i2c_bypass_select(struct i2c_mux_core *mux, u32 chan_id) > +{ > + struct sii902x *sii902x = i2c_mux_priv(mux); > + struct device *dev = &sii902x->i2c->dev; > + unsigned long timeout; > + u8 status; > + int ret; > + > + ret = sii902x_update_bits_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + SII902X_SYS_CTRL_DDC_BUS_REQ, > + SII902X_SYS_CTRL_DDC_BUS_REQ); > + > + timeout = jiffies + > + msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); > + do { > + ret = sii902x_read_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + &status); > + if (ret) > + return ret; > + } while (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD) && > + time_before(jiffies, timeout)); > + > + if (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD)) { > + dev_err(dev, "Failed to acquire the i2c bus\n"); > + return -ETIMEDOUT; > + } > + > + ret = sii902x_write_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + status); > + if (ret) > + return ret; > + return 0; > +} > + > +/* > + * The purpose of sii902x_i2c_bypass_deselect is to disable the pass through > + * mode of the HDMI transmitter. Do not use regmap from within this function, > + * only use sii902x_*_unlocked functions to read/modify/write registers. > + * We are holding the parent adapter lock here, keep this in mind before > + * adding more i2c transactions. > + */ > +static int sii902x_i2c_bypass_deselect(struct i2c_mux_core *mux, u32 chan_id) > +{ > + struct sii902x *sii902x = i2c_mux_priv(mux); > + struct device *dev = &sii902x->i2c->dev; > + unsigned long timeout; > + unsigned int retries; > + u8 status; > + int ret; > + > + /* > + * When the HDMI transmitter is in pass through mode, we need an > + * (undocumented) additional delay between STOP and START conditions > + * to guarantee the bus won't get stuck. > + */ > + udelay(30); > + > + /* > + * Sometimes the I2C bus can stall after failure to use the > + * EDID channel. Retry a few times to see if things clear > + * up, else continue anyway. > + */ > + retries = 5; > + do { > + ret = sii902x_read_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + &status); > + retries--; > + } while (ret && retries); > + if (ret) { > + dev_err(dev, "failed to read status (%d)\n", ret); > + return ret; > + } > + > + ret = sii902x_update_bits_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + SII902X_SYS_CTRL_DDC_BUS_REQ | > + SII902X_SYS_CTRL_DDC_BUS_GRTD, 0); > + if (ret) > + return ret; > + > + timeout = jiffies + > + msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); > + do { > + ret = sii902x_read_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + &status); > + if (ret) > + return ret; > + } while (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | > + SII902X_SYS_CTRL_DDC_BUS_GRTD) && > + time_before(jiffies, timeout)); > + > + if (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | > + SII902X_SYS_CTRL_DDC_BUS_GRTD)) { > + dev_err(dev, "failed to release the i2c bus\n"); > + return -ETIMEDOUT; > + } > + > + return 0; > +} > + > static int sii902x_probe(struct i2c_client *client, > const struct i2c_device_id *id) > { > @@ -375,6 +478,12 @@ static int sii902x_probe(struct i2c_client *client, > u8 chipid[4]; > int ret; > > + ret = i2c_check_functionality(client->adapter, I2C_FUNC_I2C); And then I2C_FUNC_SMBUS_BYTE_DATA here, instead of I2C_FUNC_I2C, of course. Cheers, Peter > + if (!ret) { > + dev_err(dev, "I2C adapter not suitable\n"); > + return -EIO; > + } > + > sii902x = devm_kzalloc(dev, sizeof(*sii902x), GFP_KERNEL); > if (!sii902x) > return -ENOMEM; > @@ -433,6 +542,22 @@ static int sii902x_probe(struct i2c_client *client, > > i2c_set_clientdata(client, sii902x); > > + sii902x->i2cmux = i2c_mux_alloc(client->adapter, dev, > + 1, 0, I2C_MUX_GATE, > + sii902x_i2c_bypass_select, > + sii902x_i2c_bypass_deselect); > + if (!sii902x->i2cmux) { > + dev_err(dev, "failed to allocate I2C mux\n"); > + return -ENOMEM; > + } > + > + sii902x->i2cmux->priv = sii902x; > + ret = i2c_mux_add_adapter(sii902x->i2cmux, 0, 0, 0); > + if (ret) { > + dev_err(dev, "Couldn't add i2c mux adapter\n"); > + return ret; > + } > + > return 0; > } > > @@ -441,6 +566,9 @@ static int sii902x_remove(struct i2c_client *client) > { > struct sii902x *sii902x = i2c_get_clientdata(client); > > + if (sii902x->i2cmux) > + i2c_mux_del_adapters(sii902x->i2cmux); > + > drm_bridge_remove(&sii902x->bridge); > > return 0; >
Hello Peter, Thank you for your feedback! The changes you have suggested seem to be working just fine, I have tested them this morning. Thanks, Fab > Subject: Re: [PATCH] drm/bridge/sii902x: Fix EDID readback > > On 2018-11-02 13:13, Fabrizio Castro wrote: > > While adding SiI9022A support to the iwg23s board, it came > > up that when the HDMI transmitter is in pass through mode the > > device is not compliant with the I2C specification anymore, > > as it requires a far bigger tbuf, due to a delay the HDMI > > transmitter is adding when relaying the STOP condition on the > > monitor i2c side of things. > > > > When not providing an appropriate delay after the STOP condition > > the i2c bus would get stuck. Also, any other traffic on the bus > > while talking to the monitor may cause the transaction to fail > > or even cause issues with the i2c bus as well. > > > > I2c-gates seemed to reach consent as a possible way to address > > these issues, and as such this patch is implementing a solution > > based on that. Since others are clearly relying on the current > > implementation of the driver, this patch won't require any DT > > changes. > > > > Since we don't want any interference during the DDC Bus > > Request/Grant procedure and while talking to the monitor, we > > have to use the adapter locking primitives rather than the > > i2c-mux locking primitives. > > > > Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com> > > --- > > RFC->PATCH: > > * Incorporated Linus Walleij, Peter Rosin, and Mark Brown comments > > > > Thank you guys > > > > drivers/gpu/drm/bridge/sii902x.c | 264 +++++++++++++++++++++++++++++---------- > > 1 file changed, 196 insertions(+), 68 deletions(-) > > > > diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c > > index e59a135..4f9d9c7 100644 > > --- a/drivers/gpu/drm/bridge/sii902x.c > > +++ b/drivers/gpu/drm/bridge/sii902x.c > > @@ -1,4 +1,6 @@ > > /* > > + * Copyright (C) 2018 Renesas Electronics > > + * > > * Copyright (C) 2016 Atmel > > * Bo Shen <voice.shen@atmel.com> > > * > > @@ -21,6 +23,7 @@ > > */ > > > > #include <linux/gpio/consumer.h> > > +#include <linux/i2c-mux.h> > > #include <linux/i2c.h> > > #include <linux/module.h> > > #include <linux/regmap.h> > > @@ -86,8 +89,68 @@ struct sii902x { > > struct drm_bridge bridge; > > struct drm_connector connector; > > struct gpio_desc *reset_gpio; > > +struct i2c_mux_core *i2cmux; > > }; > > > > +static int sii902x_read_unlocked(struct i2c_client *i2c, u8 reg, u8 *val) > > +{ > > +struct i2c_msg xfer[] = { > > +{ > > +.addr = i2c->addr, > > +.flags = 0, > > +.len = 1, > > +.buf = ®, > > +}, { > > +.addr = i2c->addr, > > +.flags = I2C_M_RD, > > +.len = 1, > > +.buf = val, > > +} > > +}; > > +unsigned char xfers = ARRAY_SIZE(xfer); > > +int ret, retries = 5; > > + > > +do { > > +ret = __i2c_transfer(i2c->adapter, xfer, xfers); > > +if (ret < 0) > > +return ret; > > +} while (ret != xfers && --retries); > > +return ret == xfers ? 0 : -1; > > New in 4.19 __i2c_smbus_xfer, and I think it helps here? (untested code) > > union i2c_smbus_data data; > int ret; > > ret = __i2c_smbus_xfer(i2c->adapter, i2c->addr, i2c->flags, > I2C_SMBUS_READ, reg, > I2C_SMBUS_BYTE_DATA, &data); > > if (ret < 0) > return ret; > > *val = data.byte; > return 0; > > > +} > > + > > +static int sii902x_write_unlocked(struct i2c_client *i2c, u8 reg, u8 val) > > +{ > > +u8 data[2] = {reg, val}; > > +struct i2c_msg xfer = { > > +.addr = i2c->addr, > > +.flags = 0, > > +.len = sizeof(data), > > +.buf = data, > > +}; > > +int ret, retries = 5; > > + > > +do { > > +ret = __i2c_transfer(i2c->adapter, &xfer, 1); > > +if (ret < 0) > > +return ret; > > +} while (!ret && --retries); > > +return !ret ? -1 : 0; > > union i2c_smbus_data data; > > data.byte = val; > > return __i2c_smbus_xfer(i2c->adapter, i2c->addr, i2c->flags, > I2C_SMBUS_WRITE, reg, > I2C_SMBUS_BYTE_DATA, &data); > > +} > > + > > +static int sii902x_update_bits_unlocked(struct i2c_client *i2c, u8 reg, u8 mask, > > +u8 val) > > +{ > > +int ret; > > +u8 status; > > + > > +ret = sii902x_read_unlocked(i2c, reg, &status); > > +if (ret) > > +return ret; > > +status &= ~mask; > > +status |= val & mask; > > +return sii902x_write_unlocked(i2c, reg, status); > > +} > > + > > static inline struct sii902x *bridge_to_sii902x(struct drm_bridge *bridge) > > { > > return container_of(bridge, struct sii902x, bridge); > > @@ -135,41 +198,11 @@ static const struct drm_connector_funcs sii902x_connector_funcs = { > > static int sii902x_get_modes(struct drm_connector *connector) > > { > > struct sii902x *sii902x = connector_to_sii902x(connector); > > -struct regmap *regmap = sii902x->regmap; > > u32 bus_format = MEDIA_BUS_FMT_RGB888_1X24; > > -struct device *dev = &sii902x->i2c->dev; > > -unsigned long timeout; > > -unsigned int retries; > > -unsigned int status; > > struct edid *edid; > > -int num = 0; > > -int ret; > > - > > -ret = regmap_update_bits(regmap, SII902X_SYS_CTRL_DATA, > > - SII902X_SYS_CTRL_DDC_BUS_REQ, > > - SII902X_SYS_CTRL_DDC_BUS_REQ); > > -if (ret) > > -return ret; > > - > > -timeout = jiffies + > > - msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); > > -do { > > -ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, &status); > > -if (ret) > > -return ret; > > -} while (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD) && > > - time_before(jiffies, timeout)); > > - > > -if (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD)) { > > -dev_err(dev, "failed to acquire the i2c bus\n"); > > -return -ETIMEDOUT; > > -} > > - > > -ret = regmap_write(regmap, SII902X_SYS_CTRL_DATA, status); > > -if (ret) > > -return ret; > > +int num = 0, ret; > > > > -edid = drm_get_edid(connector, sii902x->i2c->adapter); > > +edid = drm_get_edid(connector, sii902x->i2cmux->adapter[0]); > > drm_connector_update_edid_property(connector, edid); > > if (edid) { > > num = drm_add_edid_modes(connector, edid); > > @@ -181,42 +214,6 @@ static int sii902x_get_modes(struct drm_connector *connector) > > if (ret) > > return ret; > > > > -/* > > - * Sometimes the I2C bus can stall after failure to use the > > - * EDID channel. Retry a few times to see if things clear > > - * up, else continue anyway. > > - */ > > -retries = 5; > > -do { > > -ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, > > - &status); > > -retries--; > > -} while (ret && retries); > > -if (ret) > > -dev_err(dev, "failed to read status (%d)\n", ret); > > - > > -ret = regmap_update_bits(regmap, SII902X_SYS_CTRL_DATA, > > - SII902X_SYS_CTRL_DDC_BUS_REQ | > > - SII902X_SYS_CTRL_DDC_BUS_GRTD, 0); > > -if (ret) > > -return ret; > > - > > -timeout = jiffies + > > - msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); > > -do { > > -ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, &status); > > -if (ret) > > -return ret; > > -} while (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | > > - SII902X_SYS_CTRL_DDC_BUS_GRTD) && > > - time_before(jiffies, timeout)); > > - > > -if (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | > > - SII902X_SYS_CTRL_DDC_BUS_GRTD)) { > > -dev_err(dev, "failed to release the i2c bus\n"); > > -return -ETIMEDOUT; > > -} > > - > > return num; > > } > > > > @@ -366,6 +363,112 @@ static irqreturn_t sii902x_interrupt(int irq, void *data) > > return IRQ_HANDLED; > > } > > > > +/* > > + * The purpose of sii902x_i2c_bypass_select is to enable the pass through > > + * mode of the HDMI transmitter. Do not use regmap from within this function, > > + * only use sii902x_*_unlocked functions to read/modify/write registers. > > + * We are holding the parent adapter lock here, keep this in mind before > > + * adding more i2c transactions. > > + */ > > +static int sii902x_i2c_bypass_select(struct i2c_mux_core *mux, u32 chan_id) > > +{ > > +struct sii902x *sii902x = i2c_mux_priv(mux); > > +struct device *dev = &sii902x->i2c->dev; > > +unsigned long timeout; > > +u8 status; > > +int ret; > > + > > +ret = sii902x_update_bits_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > > + SII902X_SYS_CTRL_DDC_BUS_REQ, > > + SII902X_SYS_CTRL_DDC_BUS_REQ); > > + > > +timeout = jiffies + > > + msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); > > +do { > > +ret = sii902x_read_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > > + &status); > > +if (ret) > > +return ret; > > +} while (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD) && > > + time_before(jiffies, timeout)); > > + > > +if (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD)) { > > +dev_err(dev, "Failed to acquire the i2c bus\n"); > > +return -ETIMEDOUT; > > +} > > + > > +ret = sii902x_write_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > > + status); > > +if (ret) > > +return ret; > > +return 0; > > +} > > + > > +/* > > + * The purpose of sii902x_i2c_bypass_deselect is to disable the pass through > > + * mode of the HDMI transmitter. Do not use regmap from within this function, > > + * only use sii902x_*_unlocked functions to read/modify/write registers. > > + * We are holding the parent adapter lock here, keep this in mind before > > + * adding more i2c transactions. > > + */ > > +static int sii902x_i2c_bypass_deselect(struct i2c_mux_core *mux, u32 chan_id) > > +{ > > +struct sii902x *sii902x = i2c_mux_priv(mux); > > +struct device *dev = &sii902x->i2c->dev; > > +unsigned long timeout; > > +unsigned int retries; > > +u8 status; > > +int ret; > > + > > +/* > > + * When the HDMI transmitter is in pass through mode, we need an > > + * (undocumented) additional delay between STOP and START conditions > > + * to guarantee the bus won't get stuck. > > + */ > > +udelay(30); > > + > > +/* > > + * Sometimes the I2C bus can stall after failure to use the > > + * EDID channel. Retry a few times to see if things clear > > + * up, else continue anyway. > > + */ > > +retries = 5; > > +do { > > +ret = sii902x_read_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > > + &status); > > +retries--; > > +} while (ret && retries); > > +if (ret) { > > +dev_err(dev, "failed to read status (%d)\n", ret); > > +return ret; > > +} > > + > > +ret = sii902x_update_bits_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > > + SII902X_SYS_CTRL_DDC_BUS_REQ | > > + SII902X_SYS_CTRL_DDC_BUS_GRTD, 0); > > +if (ret) > > +return ret; > > + > > +timeout = jiffies + > > + msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); > > +do { > > +ret = sii902x_read_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > > + &status); > > +if (ret) > > +return ret; > > +} while (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | > > + SII902X_SYS_CTRL_DDC_BUS_GRTD) && > > + time_before(jiffies, timeout)); > > + > > +if (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | > > + SII902X_SYS_CTRL_DDC_BUS_GRTD)) { > > +dev_err(dev, "failed to release the i2c bus\n"); > > +return -ETIMEDOUT; > > +} > > + > > +return 0; > > +} > > + > > static int sii902x_probe(struct i2c_client *client, > > const struct i2c_device_id *id) > > { > > @@ -375,6 +478,12 @@ static int sii902x_probe(struct i2c_client *client, > > u8 chipid[4]; > > int ret; > > > > +ret = i2c_check_functionality(client->adapter, I2C_FUNC_I2C); > > And then I2C_FUNC_SMBUS_BYTE_DATA here, instead of I2C_FUNC_I2C, of course. > > Cheers, > Peter > > > +if (!ret) { > > +dev_err(dev, "I2C adapter not suitable\n"); > > +return -EIO; > > +} > > + > > sii902x = devm_kzalloc(dev, sizeof(*sii902x), GFP_KERNEL); > > if (!sii902x) > > return -ENOMEM; > > @@ -433,6 +542,22 @@ static int sii902x_probe(struct i2c_client *client, > > > > i2c_set_clientdata(client, sii902x); > > > > +sii902x->i2cmux = i2c_mux_alloc(client->adapter, dev, > > +1, 0, I2C_MUX_GATE, > > +sii902x_i2c_bypass_select, > > +sii902x_i2c_bypass_deselect); > > +if (!sii902x->i2cmux) { > > +dev_err(dev, "failed to allocate I2C mux\n"); > > +return -ENOMEM; > > +} > > + > > +sii902x->i2cmux->priv = sii902x; > > +ret = i2c_mux_add_adapter(sii902x->i2cmux, 0, 0, 0); > > +if (ret) { > > +dev_err(dev, "Couldn't add i2c mux adapter\n"); > > +return ret; > > +} > > + > > return 0; > > } > > > > @@ -441,6 +566,9 @@ static int sii902x_remove(struct i2c_client *client) > > { > > struct sii902x *sii902x = i2c_get_clientdata(client); > > > > +if (sii902x->i2cmux) > > +i2c_mux_del_adapters(sii902x->i2cmux); > > + > > drm_bridge_remove(&sii902x->bridge); > > > > return 0; > > Renesas Electronics Europe Ltd, Dukes Meadow, Millboard Road, Bourne End, Buckinghamshire, SL8 5FH, UK. Registered in England & Wales under Registered No. 04586709.
Hello Peter, Thank you for your feedback! > Subject: Re: [PATCH] drm/bridge/sii902x: Fix EDID readback > snip > > If the things you write about the bits are true (haven't looked closely), I wouldn't > add any regmap coordination. But if I was the maintainer, I'd like a comment about > this so that the next contributor has a better chance to understand the subtlety. > > But I'm not the maintainer, so this is not my call, but by adding the comment you > also clarify the situation for the maintainer, which is something that is likely > to be appreciated. I'll add comments then. Cheers, Fab > > Cheers, > Peter Renesas Electronics Europe Ltd, Dukes Meadow, Millboard Road, Bourne End, Buckinghamshire, SL8 5FH, UK. Registered in England & Wales under Registered No. 04586709.
diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c index e59a135..4f9d9c7 100644 --- a/drivers/gpu/drm/bridge/sii902x.c +++ b/drivers/gpu/drm/bridge/sii902x.c @@ -1,4 +1,6 @@ /* + * Copyright (C) 2018 Renesas Electronics + * * Copyright (C) 2016 Atmel * Bo Shen <voice.shen@atmel.com> * @@ -21,6 +23,7 @@ */ #include <linux/gpio/consumer.h> +#include <linux/i2c-mux.h> #include <linux/i2c.h> #include <linux/module.h> #include <linux/regmap.h> @@ -86,8 +89,68 @@ struct sii902x { struct drm_bridge bridge; struct drm_connector connector; struct gpio_desc *reset_gpio; + struct i2c_mux_core *i2cmux; }; +static int sii902x_read_unlocked(struct i2c_client *i2c, u8 reg, u8 *val) +{ + struct i2c_msg xfer[] = { + { + .addr = i2c->addr, + .flags = 0, + .len = 1, + .buf = ®, + }, { + .addr = i2c->addr, + .flags = I2C_M_RD, + .len = 1, + .buf = val, + } + }; + unsigned char xfers = ARRAY_SIZE(xfer); + int ret, retries = 5; + + do { + ret = __i2c_transfer(i2c->adapter, xfer, xfers); + if (ret < 0) + return ret; + } while (ret != xfers && --retries); + return ret == xfers ? 0 : -1; +} + +static int sii902x_write_unlocked(struct i2c_client *i2c, u8 reg, u8 val) +{ + u8 data[2] = {reg, val}; + struct i2c_msg xfer = { + .addr = i2c->addr, + .flags = 0, + .len = sizeof(data), + .buf = data, + }; + int ret, retries = 5; + + do { + ret = __i2c_transfer(i2c->adapter, &xfer, 1); + if (ret < 0) + return ret; + } while (!ret && --retries); + return !ret ? -1 : 0; +} + +static int sii902x_update_bits_unlocked(struct i2c_client *i2c, u8 reg, u8 mask, + u8 val) +{ + int ret; + u8 status; + + ret = sii902x_read_unlocked(i2c, reg, &status); + if (ret) + return ret; + status &= ~mask; + status |= val & mask; + return sii902x_write_unlocked(i2c, reg, status); +} + static inline struct sii902x *bridge_to_sii902x(struct drm_bridge *bridge) { return container_of(bridge, struct sii902x, bridge); @@ -135,41 +198,11 @@ static const struct drm_connector_funcs sii902x_connector_funcs = { static int sii902x_get_modes(struct drm_connector *connector) { struct sii902x *sii902x = connector_to_sii902x(connector); - struct regmap *regmap = sii902x->regmap; u32 bus_format = MEDIA_BUS_FMT_RGB888_1X24; - struct device *dev = &sii902x->i2c->dev; - unsigned long timeout; - unsigned int retries; - unsigned int status; struct edid *edid; - int num = 0; - int ret; - - ret = regmap_update_bits(regmap, SII902X_SYS_CTRL_DATA, - SII902X_SYS_CTRL_DDC_BUS_REQ, - SII902X_SYS_CTRL_DDC_BUS_REQ); - if (ret) - return ret; - - timeout = jiffies + - msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); - do { - ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, &status); - if (ret) - return ret; - } while (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD) && - time_before(jiffies, timeout)); - - if (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD)) { - dev_err(dev, "failed to acquire the i2c bus\n"); - return -ETIMEDOUT; - } - - ret = regmap_write(regmap, SII902X_SYS_CTRL_DATA, status); - if (ret) - return ret; + int num = 0, ret; - edid = drm_get_edid(connector, sii902x->i2c->adapter); + edid = drm_get_edid(connector, sii902x->i2cmux->adapter[0]); drm_connector_update_edid_property(connector, edid); if (edid) { num = drm_add_edid_modes(connector, edid); @@ -181,42 +214,6 @@ static int sii902x_get_modes(struct drm_connector *connector) if (ret) return ret; - /* - * Sometimes the I2C bus can stall after failure to use the - * EDID channel. Retry a few times to see if things clear - * up, else continue anyway. - */ - retries = 5; - do { - ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, - &status); - retries--; - } while (ret && retries); - if (ret) - dev_err(dev, "failed to read status (%d)\n", ret); - - ret = regmap_update_bits(regmap, SII902X_SYS_CTRL_DATA, - SII902X_SYS_CTRL_DDC_BUS_REQ | - SII902X_SYS_CTRL_DDC_BUS_GRTD, 0); - if (ret) - return ret; - - timeout = jiffies + - msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); - do { - ret = regmap_read(regmap, SII902X_SYS_CTRL_DATA, &status); - if (ret) - return ret; - } while (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | - SII902X_SYS_CTRL_DDC_BUS_GRTD) && - time_before(jiffies, timeout)); - - if (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | - SII902X_SYS_CTRL_DDC_BUS_GRTD)) { - dev_err(dev, "failed to release the i2c bus\n"); - return -ETIMEDOUT; - } - return num; } @@ -366,6 +363,112 @@ static irqreturn_t sii902x_interrupt(int irq, void *data) return IRQ_HANDLED; } +/* + * The purpose of sii902x_i2c_bypass_select is to enable the pass through + * mode of the HDMI transmitter. Do not use regmap from within this function, + * only use sii902x_*_unlocked functions to read/modify/write registers. + * We are holding the parent adapter lock here, keep this in mind before + * adding more i2c transactions. + */ +static int sii902x_i2c_bypass_select(struct i2c_mux_core *mux, u32 chan_id) +{ + struct sii902x *sii902x = i2c_mux_priv(mux); + struct device *dev = &sii902x->i2c->dev; + unsigned long timeout; + u8 status; + int ret; + + ret = sii902x_update_bits_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, + SII902X_SYS_CTRL_DDC_BUS_REQ, + SII902X_SYS_CTRL_DDC_BUS_REQ); + + timeout = jiffies + + msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); + do { + ret = sii902x_read_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, + &status); + if (ret) + return ret; + } while (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD) && + time_before(jiffies, timeout)); + + if (!(status & SII902X_SYS_CTRL_DDC_BUS_GRTD)) { + dev_err(dev, "Failed to acquire the i2c bus\n"); + return -ETIMEDOUT; + } + + ret = sii902x_write_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, + status); + if (ret) + return ret; + return 0; +} + +/* + * The purpose of sii902x_i2c_bypass_deselect is to disable the pass through + * mode of the HDMI transmitter. Do not use regmap from within this function, + * only use sii902x_*_unlocked functions to read/modify/write registers. + * We are holding the parent adapter lock here, keep this in mind before + * adding more i2c transactions. + */ +static int sii902x_i2c_bypass_deselect(struct i2c_mux_core *mux, u32 chan_id) +{ + struct sii902x *sii902x = i2c_mux_priv(mux); + struct device *dev = &sii902x->i2c->dev; + unsigned long timeout; + unsigned int retries; + u8 status; + int ret; + + /* + * When the HDMI transmitter is in pass through mode, we need an + * (undocumented) additional delay between STOP and START conditions + * to guarantee the bus won't get stuck. + */ + udelay(30); + + /* + * Sometimes the I2C bus can stall after failure to use the + * EDID channel. Retry a few times to see if things clear + * up, else continue anyway. + */ + retries = 5; + do { + ret = sii902x_read_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, + &status); + retries--; + } while (ret && retries); + if (ret) { + dev_err(dev, "failed to read status (%d)\n", ret); + return ret; + } + + ret = sii902x_update_bits_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, + SII902X_SYS_CTRL_DDC_BUS_REQ | + SII902X_SYS_CTRL_DDC_BUS_GRTD, 0); + if (ret) + return ret; + + timeout = jiffies + + msecs_to_jiffies(SII902X_I2C_BUS_ACQUISITION_TIMEOUT_MS); + do { + ret = sii902x_read_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, + &status); + if (ret) + return ret; + } while (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | + SII902X_SYS_CTRL_DDC_BUS_GRTD) && + time_before(jiffies, timeout)); + + if (status & (SII902X_SYS_CTRL_DDC_BUS_REQ | + SII902X_SYS_CTRL_DDC_BUS_GRTD)) { + dev_err(dev, "failed to release the i2c bus\n"); + return -ETIMEDOUT; + } + + return 0; +} + static int sii902x_probe(struct i2c_client *client, const struct i2c_device_id *id) { @@ -375,6 +478,12 @@ static int sii902x_probe(struct i2c_client *client, u8 chipid[4]; int ret; + ret = i2c_check_functionality(client->adapter, I2C_FUNC_I2C); + if (!ret) { + dev_err(dev, "I2C adapter not suitable\n"); + return -EIO; + } + sii902x = devm_kzalloc(dev, sizeof(*sii902x), GFP_KERNEL); if (!sii902x) return -ENOMEM; @@ -433,6 +542,22 @@ static int sii902x_probe(struct i2c_client *client, i2c_set_clientdata(client, sii902x); + sii902x->i2cmux = i2c_mux_alloc(client->adapter, dev, + 1, 0, I2C_MUX_GATE, + sii902x_i2c_bypass_select, + sii902x_i2c_bypass_deselect); + if (!sii902x->i2cmux) { + dev_err(dev, "failed to allocate I2C mux\n"); + return -ENOMEM; + } + + sii902x->i2cmux->priv = sii902x; + ret = i2c_mux_add_adapter(sii902x->i2cmux, 0, 0, 0); + if (ret) { + dev_err(dev, "Couldn't add i2c mux adapter\n"); + return ret; + } + return 0; } @@ -441,6 +566,9 @@ static int sii902x_remove(struct i2c_client *client) { struct sii902x *sii902x = i2c_get_clientdata(client); + if (sii902x->i2cmux) + i2c_mux_del_adapters(sii902x->i2cmux); + drm_bridge_remove(&sii902x->bridge); return 0;
While adding SiI9022A support to the iwg23s board, it came up that when the HDMI transmitter is in pass through mode the device is not compliant with the I2C specification anymore, as it requires a far bigger tbuf, due to a delay the HDMI transmitter is adding when relaying the STOP condition on the monitor i2c side of things. When not providing an appropriate delay after the STOP condition the i2c bus would get stuck. Also, any other traffic on the bus while talking to the monitor may cause the transaction to fail or even cause issues with the i2c bus as well. I2c-gates seemed to reach consent as a possible way to address these issues, and as such this patch is implementing a solution based on that. Since others are clearly relying on the current implementation of the driver, this patch won't require any DT changes. Since we don't want any interference during the DDC Bus Request/Grant procedure and while talking to the monitor, we have to use the adapter locking primitives rather than the i2c-mux locking primitives. Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com> --- RFC->PATCH: * Incorporated Linus Walleij, Peter Rosin, and Mark Brown comments Thank you guys drivers/gpu/drm/bridge/sii902x.c | 264 +++++++++++++++++++++++++++++---------- 1 file changed, 196 insertions(+), 68 deletions(-)