linux-kernel - Re: [PATCH v1 1/3] drm/msm/dp: move struc of msm_display_info to msm

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Date:   Sat, 25 Jun 2022 02:41:35 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc:     dri-devel@...ts.freedesktop.org, robdclark@...il.com,
        sean@...rly.run, swboyd@...omium.org, dianders@...omium.org,
        vkoul@...nel.org, daniel@...ll.ch, airlied@...ux.ie,
        agross@...nel.org, bjorn.andersson@...aro.org,
        quic_abhinavk@...cinc.com, quic_aravindh@...cinc.com,
        quic_sbillaka@...cinc.com, freedreno@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/3] drm/msm/dp: move struc of msm_display_info to msm_drv.h

On Fri, 24 Jun 2022 at 20:15, Kuogee Hsieh <quic_khsieh@...cinc.com> wrote:
>
> With current implementation, communication between interface driver and
> upper mdss encoder layer are implemented through function calls. This
> increase code complexity. Since struct msm_display_info contains msm
> generic display information, it can be expended to contains more useful
> information, such as widebus and dcs, in future to serve as communication
> channel purpose between interface driver and upper mdss encoder layer so
> that existing function calls can be eliminated.
> This patch more struct msm_display_info to msm_drv.h to be visible by
> whole msm scope.

NAK.

The msm_display_info contains information used by (and useful to) DPU
only, it is not 'msm generic' info. For this reason it has been moved
from msm_drv.h to dpu_encoder.h inIn commit b7420739f112 ("drm/msm:
move struct msm_display_info to dpu driver") . Neither mdp5 nor mdp4
are going to use this structure.

At some point I thought too that we might be able to create a set of
data and functions to describe encoder backends (dsi, hdmi, dp). This
has failed for me. After musing over the msm_drv.h part containing
functions published by the backends, I could not end up with a set of
them being good enough. The only common part seems to be the
modeset_init, snapshot and (once DP gets the DSC interface)
get_dsc_config. The rest is backend-specific.

I would suggest returning to this topic if/once DSI gets wide bus
support or DP starts using bonded interfaces. Before that I don't
foresee that common data structure would simplify things rather than
complicating them.

>
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h | 20 --------------------
>  drivers/gpu/drm/msm/msm_drv.h               | 19 +++++++++++++++++++
>  2 files changed, 19 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
> index 781d41c..6b604c5 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
> @@ -19,26 +19,6 @@
>  #define IDLE_TIMEOUT   (66 - 16/2)
>
>  /**
> - * struct msm_display_info - defines display properties
> - * @intf_type:          DRM_MODE_ENCODER_ type
> - * @capabilities:       Bitmask of display flags
> - * @num_of_h_tiles:     Number of horizontal tiles in case of split interface
> - * @h_tile_instance:    Controller instance used per tile. Number of elements is
> - *                      based on num_of_h_tiles
> - * @is_te_using_watchdog_timer:  Boolean to indicate watchdog TE is
> - *                              used instead of panel TE in cmd mode panels
> - * @dsc:               DSC configuration data for DSC-enabled displays
> - */
> -struct msm_display_info {
> -       int intf_type;
> -       uint32_t capabilities;
> -       uint32_t num_of_h_tiles;
> -       uint32_t h_tile_instance[MAX_H_TILES_PER_DISPLAY];
> -       bool is_te_using_watchdog_timer;
> -       struct msm_display_dsc_config *dsc;
> -};
> -
> -/**
>   * dpu_encoder_assign_crtc - Link the encoder to the crtc it's assigned to
>   * @encoder:   encoder pointer
>   * @crtc:      crtc pointer
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index fdbaad5..f9c263b 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -106,11 +106,30 @@ struct msm_drm_thread {
>         struct kthread_worker *worker;
>  };
>
> +<<<<<<< HEAD

Not to mention that this patch is broken per se.

>  /* DSC config */
>  struct msm_display_dsc_config {
>         struct drm_dsc_config *drm;
>  };
>
> +/**
> + * struct msm_display_info - defines display properties
> + * @intf_type:          DRM_MODE_ENCODER_ type
> + * @capabilities:       Bitmask of display flags
> + * @num_of_h_tiles:     Number of horizontal tiles in case of split interface
> + * @h_tile_instance:    Controller instance used per tile. Number of elements is
> + *                      based on num_of_h_tiles
> + * @is_te_using_watchdog_timer:  Boolean to indicate watchdog TE is
> + *                              used instead of panel TE in cmd mode panels
> + */
> +struct msm_display_info {
> +       int intf_type;
> +       uint32_t capabilities;
> +       uint32_t num_of_h_tiles;
> +       uint32_t h_tile_instance[MAX_H_TILES_PER_DISPLAY];
> +       bool is_te_using_watchdog_timer;
> +};
> +
>  struct msm_drm_private {
>
>         struct drm_device *dev;
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>
--
With best wishes
Dmitry