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

Ville Syrjälä
2016-03-09T15:13:07Z

On Mon, Mar 07, 2016 at 07:06:37PM +0200, Jani Nikula wrote:
> On Mon, 07 Mar 2016, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@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@intel.com>

Patch pushed to dinq. Thanks for the review.

>
> >
> > Cc: Jani Nikula <jani.nikula@intel.com>
> > Cc: drm-intel-fixes@lists.freedesktop.org
> > Fixes: bffce907d640 ("drm/i915: abstract i2c bit banging fallback in gmbus xfer")
> > Signed-off-by: Ville Syrjälä <ville.syrjala@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

--
Ville Syrjälä
Intel OTC