Re: [PATCH 1/3] drm/dp: WARN about invalid/unknown link rates and bw codes

From: Thierry Reding <treding@nvidia.com>
To: Jani Nikula <jani.nikula@intel.com>
Cc: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	Alex Deucher <alexander.deucher@amd.com>
Subject: Re: [PATCH 1/3] drm/dp: WARN about invalid/unknown link rates and bw codes
Date: Mon, 9 Oct 2017 12:32:07 +0200	[thread overview]
Message-ID: <20171009103207.GA14644@ulmo> (raw)
In-Reply-To: <20171009092959.29021-1-jani.nikula@intel.com>

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On Mon, Oct 09, 2017 at 12:29:57PM +0300, Jani Nikula wrote:
> Falling back to the lowest value is likely the only thing we can do, but
> doing it silently seems like a bad thing to do. Catch it early and make
> loud noises.
> 
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: Thierry Reding <treding@nvidia.com>
> Cc: Rob Clark <robdclark@gmail.com>
> Cc: Sean Paul <seanpaul@chromium.org>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 08af8d6b844b..dca21b5a03ec 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -137,8 +137,10 @@ EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay);
>  u8 drm_dp_link_rate_to_bw_code(int link_rate)
>  {
>  	switch (link_rate) {
> -	case 162000:
>  	default:
> +		WARN(1, "unknown DP link rate %d, using %x\n", link_rate,
> +		     DP_LINK_BW_1_62);
> +	case 162000:
>  		return DP_LINK_BW_1_62;
>  	case 270000:
>  		return DP_LINK_BW_2_7;
> @@ -151,8 +153,9 @@ EXPORT_SYMBOL(drm_dp_link_rate_to_bw_code);
>  int drm_dp_bw_code_to_link_rate(u8 link_bw)
>  {
>  	switch (link_bw) {
> -	case DP_LINK_BW_1_62:
>  	default:
> +		WARN(1, "unknown DP link bw code %x, using 162000\n", link_bw);

Nit: "DP link BW" because it is an abbreviation. Otherwise looks good:

Reviewed-by: Thierry Reding <treding@nvidia.com>

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