linux-kernel - Re: [PATCH v2 4/4] drm/dp_mst: Print errors on ACT timeouts

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Message-ID: <CAMavQKJ5TaTbbS2iqkcQhwCbfiXoDvG5+V1qEa509GaqjBwM2g@mail.gmail.com>
Date:   Tue, 7 Apr 2020 13:43:11 -0400
From:   Sean Paul <sean@...rly.run>
To:     Lyude Paul <lyude@...hat.com>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/4] drm/dp_mst: Print errors on ACT timeouts

On Mon, Apr 6, 2020 at 6:13 PM Lyude Paul <lyude@...hat.com> wrote:
>
> Although it's not unexpected for drm_dp_check_act_status() to fail due
> to DPCD read failures (as the hub may have just been unplugged
> suddenly), timeouts are a bit more worrying as they either mean we need
> a longer timeout value, or we aren't setting up payload allocations
> properly. So, let's start printing errors on timeouts.
>
> Signed-off-by: Lyude Paul <lyude@...hat.com>
> Cc: Sean Paul <sean@...rly.run>

Patches 1,2,4 are still

Reviewed-by: Sean Paul <sean@...rly.run>

> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index ce61964baa7c..0cbeb0f5c834 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -4499,10 +4499,14 @@ int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr)
>                                  status & DP_PAYLOAD_ACT_HANDLED || status < 0,
>                                  100, timeout_ms * USEC_PER_MSEC);
>         if (ret < 0 && status >= 0) {
> -               DRM_DEBUG_KMS("Failed to get ACT bit %d after %dms\n",
> -                             status, timeout_ms);
> +               DRM_ERROR("Failed to get ACT after %dms, last status: %02x\n",
> +                         timeout_ms, status);
>                 return -EINVAL;
>         } else if (status < 0) {
> +               /*
> +                * Failure here isn't unexpected - the hub may have
> +                * just been unplugged
> +                */
>                 DRM_DEBUG_KMS("Failed to read payload table status: %d\n",
>                               status);
>                 return status;
> --
> 2.25.1
>