Re: [PATCH v2] i2c: omap: Trigger bus recovery in lockup case

[Wolfram Sang <wsa@the-dreams.de>]

[-- Attachment #1: Type: text/plain, Size: 1177 bytes --]

On Wed, Oct 04, 2017 at 11:43:45AM +0200, Claudio Foellmi wrote:
> A very conservative check for bus activity (to prevent interference
> in multimaster setups) prevented the bus recovery methods from being
> triggered in the case that SDA or SCL was stuck low.
> This defeats the purpose of the recovery mechanism, which was introduced
> for exactly this situation (a slave device keeping SDA pulled down).
> 
> Also added a check to make sure SDA is low before attempting recovery.
> If SDA is not stuck low, recovery will not help, so we can skip it.
> 
> Note that bus lockups can persist across reboots. The only other options
> are to reset or power cycle the offending slave device, and many i2c
> slaves do not even have a reset pin.
> 
> If we see that one of the lines is low for the entire timeout duration,
> we can actually be sure that there is no other master driving the bus.
> It is therefore save for us to attempt a bus recovery.
> 
> Signed-off-by: Claudio Foellmi <claudio.foellmi@ergon.ch>
> Cc: Grygorii Strashko <grygorii.strashko@ti.com>
> Cc: Vignesh R <vigneshr@ti.com>

Applied with the discussed change to for-next, thanks!


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]