On Fri, Feb 02, 2018 at 07:56:22PM +0530, Ramalingam C wrote:
> 
> 
> On Friday 02 February 2018 07:46 PM, Sean Paul wrote:
> > On Fri, Feb 02, 2018 at 04:15:16PM +0530, Ramalingam C wrote:
> > > When BKSV is invalid, to mitigate any communication errors,
> > > BKSV is read once again.
> > Why is the Bksv read any more volatile than other reads? If the channel is
> > noisy, the retries should be done in the shim implementation (I think there 
> > are
> > already i2c retries).
> > 
> > Sean
> True. But compliance spec says that when we determine that bksv is invalid
> (not with 20 1s), we should re-read and confirm.
> CTS test 1A-05 test expect this behavior.

Ah, ok. So this is different from what you wrote in the commit message. I think
we can simplify this to make it more clear.

> 
> --Ram
> 
> > 
> > > Signed-off-by: Ramalingam C <ramalinga...@intel.com>
> > > ---
> > >   drivers/gpu/drm/i915/intel_hdcp.c | 13 +++++++++----
> > >   1 file changed, 9 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_hdcp.c 
> > > b/drivers/gpu/drm/i915/intel_hdcp.c
> > > index b3f407cef8b0..fa2e7c727d00 100644
> > > --- a/drivers/gpu/drm/i915/intel_hdcp.c
> > > +++ b/drivers/gpu/drm/i915/intel_hdcp.c
> > > @@ -401,7 +401,7 @@ static int intel_hdcp_auth(struct intel_connector 
> > > *connector)
> > >           struct drm_i915_private *dev_priv;
> > >           enum port port;
> > >           unsigned long r0_prime_gen_start;
> > > - int ret, i;
> > > + int ret, i, retry = 1;
> > >           union {
> > >                   u32 reg[2];
> > >                   u8 shim[DRM_HDCP_AN_LEN];
> > > @@ -443,11 +443,16 @@ static int intel_hdcp_auth(struct intel_connector 
> > > *connector)
> > >           r0_prime_gen_start = jiffies;
> > >           memset(&bksv, 0, sizeof(bksv));
> > > - ret = shim->read_bksv(intel_dig_port, bksv.shim);
> > > +
> > > + do {
> > > +         ret = shim->read_bksv(intel_dig_port, bksv.shim);
> > > +         if (!ret)
> > > +                 if (!intel_hdcp_is_ksv_valid(bksv.shim))
> > > +                         ret = -ENODEV;
> > > + } while (ret && retry--);


        /* HDCP spec states that we must retry the bksv if it is invalid */
        for (i = 0; i < bksv_tries; i++) {
                ret = shim->read_bksv(intel_dig_port, bksv.shim);
                if (ret)
                        return ret;
                if (intel_hdcp_is_ksv_valid(bksv.shim))
                        break;
        }
        if (i == bksv_tries)
                return -ENODEV;



> > > +
> > >           if (ret)
> > >                   return ret;
> > > - else if (!intel_hdcp_is_ksv_valid(bksv.shim))
> > > -         return -ENODEV;
> > >           I915_WRITE(PORT_HDCP_BKSVLO(port), bksv.reg[0]);
> > >           I915_WRITE(PORT_HDCP_BKSVHI(port), bksv.reg[1]);
> > > -- 
> > > 2.7.4
> > > 
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS
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