[Intel-gfx] [PATCH 1/4] drm/i915: Actually retry with bit-banging after GMBUS timeout

[Jani Nikula]

On Mon, 07 Mar 2016, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> After the GMBUS transfer times out, we set force_bit=1 and
> return -EAGAIN expecting the i2c core to call the .master_xfer
> hook again so that we will retry the same transfer via bit-banging.
> This is in case the gmbus hardware is somehow faulty.
>
> Unfortunately we left adapter->retries to 0, meaning the i2c core
> didn't actually do the retry. Let's tell the core we want one retry
> when we return -EAGAIN.
>
> Note that i2c-algo-bit also uses this retry count for some internal
> retries, so we'll end up increasing those a bit as well.

I think I must have confused this with the dp aux i2c adapter retries
which does get initialized to 3. Meh.

Reviewed-by: Jani Nikula <jani.nikula at intel.com>


>
> Cc: Jani Nikula <jani.nikula at intel.com>
> Cc: drm-intel-fixes at lists.freedesktop.org
> Fixes: bffce907d640 ("drm/i915: abstract i2c bit banging fallback in gmbus xfer")
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_i2c.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
> index deb8282c26d8..52fbe530fc9e 100644
> --- a/drivers/gpu/drm/i915/intel_i2c.c
> +++ b/drivers/gpu/drm/i915/intel_i2c.c
> @@ -664,6 +664,12 @@ int intel_setup_gmbus(struct drm_device *dev)
>  
>  		bus->adapter.algo = &gmbus_algorithm;
>  
> +		/*
> +		 * We wish to retry with bit banging
> +		 * after a timed out GMBUS attempt.
> +		 */
> +		bus->adapter.retries = 1;
> +
>  		/* By default use a conservative clock rate */
>  		bus->reg0 = pin | GMBUS_RATE_100KHZ;

-- 
Jani Nikula, Intel Open Source Technology Center