[Intel-gfx] [PATCH 03/12] drm/i915: Add counters in the drm_dp_aux struct for I2C NACKs and DEFERs

[Paulo Zanoni]

2014-07-14 16:10 GMT-03:00 Todd Previte <tprevite at gmail.com>:
> These counters are used for Displayort complinace testing to detect error conditions
> when executing certain compliance tests. Currently these are used in the EDID tests
> to determine if the video mode needs to be set to the preferred mode or the failsafe
> mode.
>

It would be nice if you could cite on the commit message the name of
the specification and the name of the test(s) that use it.

Usually when I have patches that touch things outside
drivers/gpu/drm/i915, I add a Cc tag so I don't forget to email the
appropriate list:

Cc: dri-devel at lists.freedesktop.org
> Signed-off-by: Todd Previte <tprevite at gmail.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 2 ++
>  include/drm/drm_dp_helper.h     | 1 +
>  2 files changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 08e33b8..8353051 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -654,10 +654,12 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
>
>                 case DP_AUX_I2C_REPLY_NACK:
>                         DRM_DEBUG_KMS("I2C nack\n");
> +                       aux->i2c_nack_count++;
>                         return -EREMOTEIO;
>
>                 case DP_AUX_I2C_REPLY_DEFER:
>                         DRM_DEBUG_KMS("I2C defer\n");
> +                       aux->i2c_defer_count++;
>                         usleep_range(400, 500);
>                         continue;
>
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index a21568b..3749cb4 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -550,6 +550,7 @@ struct drm_dp_aux {
>         struct mutex hw_mutex;
>         ssize_t (*transfer)(struct drm_dp_aux *aux,
>                             struct drm_dp_aux_msg *msg);
> +       uint8_t i2c_nack_count, i2c_defer_count;

Does it really need to be uint8_t? I see on patch 7 that you don't
really write this value to a place that only accepts uint8_t-sized
arguments, so I fear that if we get 256 NACKs or DEFERs we may end up
doing the wrong thing.

Also, why don't we need to count the native NACKs and DEFERs?

>  };
>
>  ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
> --
> 1.9.1
>
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-- 
Paulo Zanoni