Re: [PATCH] drm/amd/display: Fix error returned by program_hpd_filter

From: Harry Wentland <hwentlan@amd.com>
To: Aditya Pakki <pakki001@umn.edu>
Cc: dri-devel@lists.freedesktop.org,
	"Chris Park" <Chris.Park@amd.com>,
	"Eric Yang" <Eric.Yang2@amd.com>, "Leo Li" <sunpeng.li@amd.com>,
	"Bhawanpreet Lakha" <Bhawanpreet.Lakha@amd.com>,
	"David Francis" <David.Francis@amd.com>,
	kjlu@umn.edu, linux-kernel@vger.kernel.org,
	amd-gfx@lists.freedesktop.org,
	"Nikola Cornij" <nikola.cornij@amd.com>,
	"David Airlie" <airlied@linux.ie>,
	"Eric Bernstein" <eric.bernstein@amd.com>,
	"David Galiffi" <david.galiffi@amd.com>,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Wenjing Liu" <Wenjing.Liu@amd.com>, "Jun Lei" <Jun.Lei@amd.com>,
	"Christian König" <christian.koenig@amd.com>,
	"Anthony Koo" <Anthony.Koo@amd.com>
Subject: Re: [PATCH] drm/amd/display: Fix error returned by program_hpd_filter
Date: Tue, 31 Dec 2019 10:08:29 -0500	[thread overview]
Message-ID: <b176fd4b-b2d3-8741-e1d7-f9b0899bc24e@amd.com> (raw)
In-Reply-To: <20191117172236.2140-1-pakki001@umn.edu>

On 2019-11-17 12:22 p.m., Aditya Pakki wrote:
> program_hpd_filter() currently fails to check for the errors
> returned in construct(). This patch returns error in
> case of failure.
> 
> Signed-off-by: Aditya Pakki <pakki001@umn.edu>
> ---
>  drivers/gpu/drm/amd/display/dc/core/dc_link.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> index ca20b150afcc..bbb648a50c41 100644
> --- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> @@ -1379,9 +1379,8 @@ static bool construct(
>  	 * If GPIO isn't programmed correctly HPD might not rise or drain
>  	 * fast enough, leading to bounces.
>  	 */
> -	program_hpd_filter(link);
> +	return program_hpd_filter(link);

We don't want program_hpd_filter to become a fatal error, which this
would do.

Though it would be good to print a warning if program_hpd_filter fails
as it's unexpected and might lead to bugs with some displays. In many
cases failing to program the HPD filter won't lead to adverse behavior.

Harry

>  
> -	return true;
>  device_tag_fail:
>  	link->link_enc->funcs->destroy(&link->link_enc);
>  link_enc_create_fail:
> 
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