| Message ID | 1541505156-8097-1-git-send-email-fabrizio.castro@bp.renesas.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Geert Uytterhoeven |
| Headers | show |
| Series | [v3] drm/bridge/sii902x: Fix EDID readback | expand |
On 2018-11-06 12:52, 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> Reviewed-by: Peter Rosin <peda@axentia.se>
On Tue, 6 Nov 2018 11:52:36 +0000 Fabrizio Castro <fabrizio.castro@bp.renesas.com> 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> Acked-by: Boris Brezillon <boris.brezillon@bootlin.com> > > --- > v2->v3: > * Incorporated comments from Boris Brezillon and Peter Rosin > > v1->v2: > * Incorporated comments from Peter Rosin > > drivers/gpu/drm/bridge/sii902x.c | 247 ++++++++++++++++++++++++++++----------- > 1 file changed, 178 insertions(+), 69 deletions(-) > > diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c > index e59a135..bfa9020 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 +89,49 @@ 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) > +{ > + 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) > +{ > + 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 +179,11 @@ 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)); > + int num = 0, ret; > > - 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; > - > - 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 +195,6 @@ 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 +344,121 @@ 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. > + * > + * Also, since SII902X_SYS_CTRL_DATA is used with regmap_update_bits elsewhere > + * in this driver, we need to make sure that we only touch 0x1A[2:1] from > + * within sii902x_i2c_bypass_select and sii902x_i2c_bypass_deselect, and that > + * we leave the remaining bits as we have found them. > + */ > +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); > + 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_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; > + } > + > + return sii902x_write_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + status); > +} > + > +/* > + * 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. > + * > + * Also, since SII902X_SYS_CTRL_DATA is used with regmap_update_bits elsewhere > + * in this driver, we need to make sure that we only touch 0x1A[2:1] from > + * within sii902x_i2c_bypass_select and sii902x_i2c_bypass_deselect, and that > + * we leave the remaining bits as we have found them. > + */ > +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 +468,13 @@ static int sii902x_probe(struct i2c_client *client, > u8 chipid[4]; > int ret; > > + ret = i2c_check_functionality(client->adapter, > + I2C_FUNC_SMBUS_BYTE_DATA); > + if (!ret) { > + dev_err(dev, "I2C adapter not suitable\n"); > + return -EIO; > + } > + > sii902x = devm_kzalloc(dev, sizeof(*sii902x), GFP_KERNEL); > if (!sii902x) > return -ENOMEM; > @@ -433,7 +533,15 @@ static int sii902x_probe(struct i2c_client *client, > > i2c_set_clientdata(client, sii902x); > > - return 0; > + sii902x->i2cmux = i2c_mux_alloc(client->adapter, dev, > + 1, 0, I2C_MUX_GATE, > + sii902x_i2c_bypass_select, > + sii902x_i2c_bypass_deselect); > + if (!sii902x->i2cmux) > + return -ENOMEM; > + > + sii902x->i2cmux->priv = sii902x; > + return i2c_mux_add_adapter(sii902x->i2cmux, 0, 0, 0); > } > > static int sii902x_remove(struct i2c_client *client) > @@ -441,6 +549,7 @@ static int sii902x_remove(struct i2c_client *client) > { > struct sii902x *sii902x = i2c_get_clientdata(client); > > + i2c_mux_del_adapters(sii902x->i2cmux); > drm_bridge_remove(&sii902x->bridge); > > return 0;
On Tue, Nov 6, 2018 at 12:52 PM Fabrizio Castro <fabrizio.castro@bp.renesas.com> 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> > > --- > v2->v3: > * Incorporated comments from Boris Brezillon and Peter Rosin Acked-by: Linus Walleij <linus.walleij@linaro.org> Do you need help to apply this to drm-misc or do you have commit access? Yours, Linus Walleij
On Thu, 15 Nov 2018 11:13:52 +0100 Linus Walleij <linus.walleij@linaro.org> wrote: > On Tue, Nov 6, 2018 at 12:52 PM Fabrizio Castro > <fabrizio.castro@bp.renesas.com> 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> > > > > --- > > v2->v3: > > * Incorporated comments from Boris Brezillon and Peter Rosin > > Acked-by: Linus Walleij <linus.walleij@linaro.org> > > Do you need help to apply this to drm-misc or do you > have commit access? I can do it if needed.
On 2018-11-06 12:52, 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> Reviewed-by: Peter Rosin <peda@axentia.se> Cheers, Peter > > --- > v2->v3: > * Incorporated comments from Boris Brezillon and Peter Rosin > > v1->v2: > * Incorporated comments from Peter Rosin > > drivers/gpu/drm/bridge/sii902x.c | 247 ++++++++++++++++++++++++++++----------- > 1 file changed, 178 insertions(+), 69 deletions(-)
Hello Boris, > From: Boris Brezillon <boris.brezillon@bootlin.com> > Sent: 15 November 2018 10:16 > Subject: Re: [PATCH v3] drm/bridge/sii902x: Fix EDID readback > > On Thu, 15 Nov 2018 11:13:52 +0100 > Linus Walleij <linus.walleij@linaro.org> wrote: > > > On Tue, Nov 6, 2018 at 12:52 PM Fabrizio Castro > > <fabrizio.castro@bp.renesas.com> 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> > > > > > > --- > > > v2->v3: > > > * Incorporated comments from Boris Brezillon and Peter Rosin > > > > Acked-by: Linus Walleij <linus.walleij@linaro.org> > > > > Do you need help to apply this to drm-misc or do you > > have commit access? > > I can do it if needed. Yes, please, your help is very much appreciated. Thanks, Fab Renesas Electronics Europe Ltd, Dukes Meadow, Millboard Road, Bourne End, Buckinghamshire, SL8 5FH, UK. Registered in England & Wales under Registered No. 04586709.
Hello Fabrizio, Many thanks for your patch. It's very helpful. Tested-by: Yannick Fertré <yannick.fertre@st.com> Best regards Yannick Fertré > Subject: [PATCH v3] drm/bridge/sii902x: Fix EDID readback > Date: Tue, 6 Nov 2018 11:52:36 +0000 > From: Fabrizio Castro <fabrizio.castro@bp.renesas.com> > To: Archit Taneja <architt@codeaurora.org>, Andrzej Hajda > <a.hajda@samsung.com>, David Airlie <airlied@linux.ie>, Peter Rosin > <peda@axentia.se>, Wolfram Sang <wsa@the-dreams.de>, Mark Brown > <broonie@kernel.org> > CC: Fabrizio Castro <fabrizio.castro@bp.renesas.com>, Chris Paterson > <Chris.Paterson2@renesas.com>, Geert Uytterhoeven > <geert+renesas@glider.be>, Boris Brezillon > <boris.brezillon@free-electrons.com>, dri-devel@lists.freedesktop.org > <dri-devel@lists.freedesktop.org>, Biju Das <biju.das@bp.renesas.com>, > linux-renesas-soc@vger.kernel.org <linux-renesas-soc@vger.kernel.org>, > Simon Horman <horms@verge.net.au>, Laurent Pinchart > <Laurent.pinchart@ideasonboard.com>, linux-i2c@vger.kernel.org > <linux-i2c@vger.kernel.org> > > 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> > > --- > v2->v3: > * Incorporated comments from Boris Brezillon and Peter Rosin > > v1->v2: > * Incorporated comments from Peter Rosin > > drivers/gpu/drm/bridge/sii902x.c | 247 > ++++++++++++++++++++++++++++----------- > 1 file changed, 178 insertions(+), 69 deletions(-) > > diff --git a/drivers/gpu/drm/bridge/sii902x.c > b/drivers/gpu/drm/bridge/sii902x.c > index e59a135..bfa9020 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 +89,49 @@ 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) > +{ > + 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) > +{ > + 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 +179,11 @@ 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)); > + int num = 0, ret; > - 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; > - > - 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 +195,6 @@ 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 +344,121 @@ 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. > + * > + * Also, since SII902X_SYS_CTRL_DATA is used with regmap_update_bits > elsewhere > + * in this driver, we need to make sure that we only touch 0x1A[2:1] from > + * within sii902x_i2c_bypass_select and sii902x_i2c_bypass_deselect, > and that > + * we leave the remaining bits as we have found them. > + */ > +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); > + 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_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; > + } > + > + return sii902x_write_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, > + status); > +} > + > +/* > + * 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. > + * > + * Also, since SII902X_SYS_CTRL_DATA is used with regmap_update_bits > elsewhere > + * in this driver, we need to make sure that we only touch 0x1A[2:1] from > + * within sii902x_i2c_bypass_select and sii902x_i2c_bypass_deselect, > and that > + * we leave the remaining bits as we have found them. > + */ > +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 +468,13 @@ static int sii902x_probe(struct i2c_client *client, > u8 chipid[4]; > int ret; > + ret = i2c_check_functionality(client->adapter, > + I2C_FUNC_SMBUS_BYTE_DATA); > + if (!ret) { > + dev_err(dev, "I2C adapter not suitable\n"); > + return -EIO; > + } > + > sii902x = devm_kzalloc(dev, sizeof(*sii902x), GFP_KERNEL); > if (!sii902x) > return -ENOMEM; > @@ -433,7 +533,15 @@ static int sii902x_probe(struct i2c_client *client, > i2c_set_clientdata(client, sii902x); > - return 0; > + sii902x->i2cmux = i2c_mux_alloc(client->adapter, dev, > + 1, 0, I2C_MUX_GATE, > + sii902x_i2c_bypass_select, > + sii902x_i2c_bypass_deselect); > + if (!sii902x->i2cmux) > + return -ENOMEM; > + > + sii902x->i2cmux->priv = sii902x; > + return i2c_mux_add_adapter(sii902x->i2cmux, 0, 0, 0); > } > static int sii902x_remove(struct i2c_client *client) > @@ -441,6 +549,7 @@ static int sii902x_remove(struct i2c_client *client) > { > struct sii902x *sii902x = i2c_get_clientdata(client); > + i2c_mux_del_adapters(sii902x->i2cmux); > drm_bridge_remove(&sii902x->bridge); > return 0;
On Thu, 15 Nov 2018 11:39:30 +0000 Fabrizio Castro <fabrizio.castro@bp.renesas.com> wrote: > Hello Boris, > > > From: Boris Brezillon <boris.brezillon@bootlin.com> > > Sent: 15 November 2018 10:16 > > Subject: Re: [PATCH v3] drm/bridge/sii902x: Fix EDID readback > > > > On Thu, 15 Nov 2018 11:13:52 +0100 > > Linus Walleij <linus.walleij@linaro.org> wrote: > > > > > On Tue, Nov 6, 2018 at 12:52 PM Fabrizio Castro > > > <fabrizio.castro@bp.renesas.com> 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> > > > > > > > > --- > > > > v2->v3: > > > > * Incorporated comments from Boris Brezillon and Peter Rosin > > > > > > Acked-by: Linus Walleij <linus.walleij@linaro.org> > > > > > > Do you need help to apply this to drm-misc or do you > > > have commit access? > > > > I can do it if needed. > > Yes, please, your help is very much appreciated. Queued to drm-misc-next. Thanks, Boris
diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c index e59a135..bfa9020 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 +89,49 @@ 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) +{ + 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) +{ + 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 +179,11 @@ 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)); + int num = 0, ret; - 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; - - 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 +195,6 @@ 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 +344,121 @@ 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. + * + * Also, since SII902X_SYS_CTRL_DATA is used with regmap_update_bits elsewhere + * in this driver, we need to make sure that we only touch 0x1A[2:1] from + * within sii902x_i2c_bypass_select and sii902x_i2c_bypass_deselect, and that + * we leave the remaining bits as we have found them. + */ +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); + 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_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; + } + + return sii902x_write_unlocked(sii902x->i2c, SII902X_SYS_CTRL_DATA, + status); +} + +/* + * 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. + * + * Also, since SII902X_SYS_CTRL_DATA is used with regmap_update_bits elsewhere + * in this driver, we need to make sure that we only touch 0x1A[2:1] from + * within sii902x_i2c_bypass_select and sii902x_i2c_bypass_deselect, and that + * we leave the remaining bits as we have found them. + */ +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 +468,13 @@ static int sii902x_probe(struct i2c_client *client, u8 chipid[4]; int ret; + ret = i2c_check_functionality(client->adapter, + I2C_FUNC_SMBUS_BYTE_DATA); + if (!ret) { + dev_err(dev, "I2C adapter not suitable\n"); + return -EIO; + } + sii902x = devm_kzalloc(dev, sizeof(*sii902x), GFP_KERNEL); if (!sii902x) return -ENOMEM; @@ -433,7 +533,15 @@ static int sii902x_probe(struct i2c_client *client, i2c_set_clientdata(client, sii902x); - return 0; + sii902x->i2cmux = i2c_mux_alloc(client->adapter, dev, + 1, 0, I2C_MUX_GATE, + sii902x_i2c_bypass_select, + sii902x_i2c_bypass_deselect); + if (!sii902x->i2cmux) + return -ENOMEM; + + sii902x->i2cmux->priv = sii902x; + return i2c_mux_add_adapter(sii902x->i2cmux, 0, 0, 0); } static int sii902x_remove(struct i2c_client *client) @@ -441,6 +549,7 @@ static int sii902x_remove(struct i2c_client *client) { struct sii902x *sii902x = i2c_get_clientdata(client); + 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> --- v2->v3: * Incorporated comments from Boris Brezillon and Peter Rosin v1->v2: * Incorporated comments from Peter Rosin drivers/gpu/drm/bridge/sii902x.c | 247 ++++++++++++++++++++++++++++----------- 1 file changed, 178 insertions(+), 69 deletions(-)