linux-kernel - Re: [PATCH v3 2/6] drm/msm: add support for per-CRTC max_vblank

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Message-ID: <CAOCk7NppkmSPrfVRAbDnmV=RQ5Rcn4d3xSKZND50gRTG=1K_kg@mail.gmail.com>
Date:   Mon, 3 Jun 2019 08:54:59 -0600
From:   Jeffrey Hugo <jeffrey.l.hugo@...il.com>
To:     Brian Masney <masneyb@...tation.org>
Cc:     Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        MSM <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Dave Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        lkml <linux-kernel@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Jonathan Marek <jonathan@...ek.ca>,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v3 2/6] drm/msm: add support for per-CRTC max_vblank_count
 on mdp5

On Fri, May 31, 2019 at 3:46 AM Brian Masney <masneyb@...tation.org> wrote:
>
> The mdp5 drm/kms driver currently does not work on command-mode DSI
> panels due to 'vblank wait timed out' errors. This causes a latency
> of seconds, or tens of seconds in some cases, before content is shown
> on the panel. This hardware does not have the something that we can use
> as a frame counter available when running in command mode, so we need to
> fall back to using timestamps by setting the max_vblank_count to zero.
> This can be done on a per-CRTC basis, so the convert mdp5 to use
> drm_crtc_set_max_vblank_count().
>
> This change was tested on a LG Nexus 5 (hammerhead) phone.
>
> Signed-off-by: Brian Masney <masneyb@...tation.org>
> Suggested-by: Jeffrey Hugo <jeffrey.l.hugo@...il.com>

Reviewed-by: Jeffrey Hugo <jeffrey.l.hugo@...il.com>

> ---
>  drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c | 16 +++++++++++++++-
>  drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c  |  2 +-
>  2 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
> index c3751c95b452..6fde1097844f 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_crtc.c
> @@ -450,6 +450,18 @@ static void mdp5_crtc_atomic_disable(struct drm_crtc *crtc,
>         mdp5_crtc->enabled = false;
>  }
>
> +static void mdp5_crtc_vblank_on(struct drm_crtc *crtc)
> +{
> +       struct mdp5_crtc_state *mdp5_cstate = to_mdp5_crtc_state(crtc->state);
> +       struct mdp5_interface *intf = mdp5_cstate->pipeline.intf;
> +       u32 count;
> +
> +       count = intf->mode == MDP5_INTF_DSI_MODE_COMMAND ? 0 : 0xffffffff;
> +       drm_crtc_set_max_vblank_count(crtc, count);
> +
> +       drm_crtc_vblank_on(crtc);
> +}
> +
>  static void mdp5_crtc_atomic_enable(struct drm_crtc *crtc,
>                                     struct drm_crtc_state *old_state)
>  {
> @@ -486,7 +498,7 @@ static void mdp5_crtc_atomic_enable(struct drm_crtc *crtc,
>         }
>
>         /* Restore vblank irq handling after power is enabled */
> -       drm_crtc_vblank_on(crtc);
> +       mdp5_crtc_vblank_on(crtc);
>
>         mdp5_crtc_mode_set_nofb(crtc);
>
> @@ -1039,6 +1051,8 @@ static void mdp5_crtc_reset(struct drm_crtc *crtc)
>                 mdp5_crtc_destroy_state(crtc, crtc->state);
>
>         __drm_atomic_helper_crtc_reset(crtc, &mdp5_cstate->base);
> +
> +       drm_crtc_vblank_reset(crtc);
>  }
>
>  static const struct drm_crtc_funcs mdp5_crtc_funcs = {
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
> index 97179bec8902..fcb0b0455abe 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
> @@ -750,7 +750,7 @@ struct msm_kms *mdp5_kms_init(struct drm_device *dev)
>         dev->driver->get_vblank_timestamp = drm_calc_vbltimestamp_from_scanoutpos;
>         dev->driver->get_scanout_position = mdp5_get_scanoutpos;
>         dev->driver->get_vblank_counter = mdp5_get_vblank_counter;
> -       dev->max_vblank_count = 0xffffffff;
> +       dev->max_vblank_count = 0; /* max_vblank_count is set on each CRTC */
>         dev->vblank_disable_immediate = true;
>
>         return kms;
> --
> 2.20.1
>