Re: [PATCH v2 8/9] i2c: riic: Add `riic_bus_barrier()` to check bus availability

Wolfram Sang
2024-12-20T21:27:02Z

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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>

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