| Message ID | 20241218001618.488946-9-prabhakar.mahadev-lad.rj@bp.renesas.com (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Geert Uytterhoeven |
| Headers | show |
| Series | Add support for I2C bus recovery for riic driver | expand |
On Wed, Dec 18, 2024 at 1:16 AM Prabhakar <prabhakar.csengg@gmail.com> wrote: > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> > > Introduce a new `riic_bus_barrier()` function to verify bus availability > before initiating an I2C transfer. This function enhances the bus > arbitration check by ensuring that the SDA and SCL lines are not held low, > in addition to checking the BBSY flag using `readb_poll_timeout()`. > > Previously, only the BBSY flag was checked to determine bus availability. > However, it is possible for the SDA line to remain low even when BBSY = 0. > This new implementation performs an additional check on the SDA and SCL > lines to avoid potential bus contention issues. > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> > --- > v1->v2 > - Used single register read to check SDA/SCL lines Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> Gr{oetje,eeting}s, Geert
On Wed, Dec 18, 2024 at 12:16:17AM +0000, Prabhakar wrote: > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> > > Introduce a new `riic_bus_barrier()` function to verify bus availability > before initiating an I2C transfer. This function enhances the bus > arbitration check by ensuring that the SDA and SCL lines are not held low, > in addition to checking the BBSY flag using `readb_poll_timeout()`. > > Previously, only the BBSY flag was checked to determine bus availability. > However, it is possible for the SDA line to remain low even when BBSY = 0. > This new implementation performs an additional check on the SDA and SCL > lines to avoid potential bus contention issues. > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> ... > - if (riic_readb(riic, RIIC_ICCR2) & ICCR2_BBSY) { > - riic->err = -EBUSY; > + riic->err = riic_bus_barrier(riic); > + if (riic->err) > goto out; > - } > > reinit_completion(&riic->msg_done); > riic->err = 0; This initialization can go now. err is 0 already. With that fixed: Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
diff --git a/drivers/i2c/busses/i2c-riic.c b/drivers/i2c/busses/i2c-riic.c index a2d0cde5ac54..586092454bb2 100644 --- a/drivers/i2c/busses/i2c-riic.c +++ b/drivers/i2c/busses/i2c-riic.c @@ -40,6 +40,7 @@ #include <linux/i2c.h> #include <linux/interrupt.h> #include <linux/io.h> +#include <linux/iopoll.h> #include <linux/module.h> #include <linux/of.h> #include <linux/platform_device.h> @@ -50,6 +51,8 @@ #define ICCR1_ICE BIT(7) #define ICCR1_IICRST BIT(6) #define ICCR1_SOWP BIT(4) +#define ICCR1_SCLI BIT(1) +#define ICCR1_SDAI BIT(0) #define ICCR2_BBSY BIT(7) #define ICCR2_SP BIT(3) @@ -135,6 +138,27 @@ static inline void riic_clear_set_bit(struct riic_dev *riic, u8 clear, u8 set, u riic_writeb(riic, (riic_readb(riic, reg) & ~clear) | set, reg); } +static int riic_bus_barrier(struct riic_dev *riic) +{ + int ret; + u8 val; + + /* + * The SDA line can still be low even when BBSY = 0. Therefore, after checking + * the BBSY flag, also verify that the SDA and SCL lines are not being held low. + */ + ret = readb_poll_timeout(riic->base + riic->info->regs[RIIC_ICCR2], val, + !(val & ICCR2_BBSY), 10, riic->adapter.timeout); + if (ret) + return -EBUSY; + + if ((riic_readb(riic, RIIC_ICCR1) & (ICCR1_SDAI | ICCR1_SCLI)) != + (ICCR1_SDAI | ICCR1_SCLI)) + return -EBUSY; + + return 0; +} + static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num) { struct riic_dev *riic = i2c_get_adapdata(adap); @@ -147,10 +171,9 @@ static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num) if (ret) return ret; - if (riic_readb(riic, RIIC_ICCR2) & ICCR2_BBSY) { - riic->err = -EBUSY; + riic->err = riic_bus_barrier(riic); + if (riic->err) goto out; - } reinit_completion(&riic->msg_done); riic->err = 0;