Hi Prabhakar,
On Fri, Dec 13, 2024 at 6:58 PM Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxx>
Thanks for your patch!
> --- a/drivers/i2c/busses/i2c-riic.c
> +++ b/drivers/i2c/busses/i2c-riic.c
> @@ -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) ||
> + !(riic_readb(riic, RIIC_ICCR1) & ICCR1_SCLI))
Surely you can read the register once, and check both bits?
> + 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);
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
