linux-kernel - Re: [PATCH 04/21] drm/msm/dsi: support DSC configurations with slice_per

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Message-ID: <CAA8EJprKnd269S_KMVUDk7UfT-c4ighPq4VkX-nEkwGg8ys1cQ@mail.gmail.com>
Date: Thu, 29 Aug 2024 14:04:34 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Jun Nie <jun.nie@...aro.org>
Cc: Rob Clark <robdclark@...il.com>, Abhinav Kumar <quic_abhinavk@...cinc.com>, 
	Sean Paul <sean@...rly.run>, Marijn Suijten <marijn.suijten@...ainline.org>, 
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, linux-arm-msm@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, Jonathan Marek <jonathan@...ek.ca>
Subject: Re: [PATCH 04/21] drm/msm/dsi: support DSC configurations with
 slice_per_pkt > 1

On Thu, 29 Aug 2024 at 13:19, Jun Nie <jun.nie@...aro.org> wrote:
>
> From: Jonathan Marek <jonathan@...ek.ca>
>
> MSM display controller support multiple slice to be sent in a single DSC
> packet.

This is not MSM-specific. It is allowed per the standard.

> Add a dsc_slice_per_pkt field to mipi_dsi_device struct and
> support this field in msm mdss driver.

This doesn't describe why this is necessary at all. Is it a fix or a feature?

>
> Note that the removed "pkt_per_line = slice_per_intf * slice_per_pkt"
> comment is incorrect.
>
> Signed-off-by: Jonathan Marek <jonathan@...ek.ca>
> Signed-off-by: Jun Nie <jun.nie@...aro.org>
> ---
>  drivers/gpu/drm/msm/dsi/dsi_host.c | 25 ++++++++++---------------
>  include/drm/drm_mipi_dsi.h         |  2 ++
>  2 files changed, 12 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index 5abade8f26b88..36f0470cdf588 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -157,6 +157,7 @@ struct msm_dsi_host {
>
>         struct drm_display_mode *mode;
>         struct drm_dsc_config *dsc;
> +       unsigned int dsc_slice_per_pkt;
>
>         /* connected device info */
>         unsigned int channel;
> @@ -861,17 +862,10 @@ static void dsi_update_dsc_timing(struct msm_dsi_host *msm_host, bool is_cmd_mod
>         slice_per_intf = msm_dsc_get_slices_per_intf(dsc, hdisplay);
>
>         total_bytes_per_intf = dsc->slice_chunk_size * slice_per_intf;
> -       bytes_per_pkt = dsc->slice_chunk_size; /* * slice_per_pkt; */
> +       bytes_per_pkt = dsc->slice_chunk_size * msm_host->dsc_slice_per_pkt;
>
>         eol_byte_num = total_bytes_per_intf % 3;
> -
> -       /*
> -        * Typically, pkt_per_line = slice_per_intf * slice_per_pkt.
> -        *
> -        * Since the current driver only supports slice_per_pkt = 1,
> -        * pkt_per_line will be equal to slice per intf for now.
> -        */
> -       pkt_per_line = slice_per_intf;
> +       pkt_per_line = slice_per_intf / msm_host->dsc_slice_per_pkt;
>
>         if (is_cmd_mode) /* packet data type */
>                 reg = DSI_COMMAND_COMPRESSION_MODE_CTRL_STREAM0_DATATYPE(MIPI_DSI_DCS_LONG_WRITE);
> @@ -1019,12 +1013,8 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
>                 else
>                         /*
>                          * When DSC is enabled, WC = slice_chunk_size * slice_per_pkt + 1.
> -                        * Currently, the driver only supports default value of slice_per_pkt = 1
> -                        *
> -                        * TODO: Expand mipi_dsi_device struct to hold slice_per_pkt info
> -                        *       and adjust DSC math to account for slice_per_pkt.
>                          */
> -                       wc = msm_host->dsc->slice_chunk_size + 1;
> +                       wc = msm_host->dsc->slice_chunk_size * msm_host->dsc_slice_per_pkt + 1;
>
>                 dsi_write(msm_host, REG_DSI_CMD_MDP_STREAM0_CTRL,
>                         DSI_CMD_MDP_STREAM0_CTRL_WORD_COUNT(wc) |
> @@ -1629,8 +1619,13 @@ static int dsi_host_attach(struct mipi_dsi_host *host,
>         msm_host->lanes = dsi->lanes;
>         msm_host->format = dsi->format;
>         msm_host->mode_flags = dsi->mode_flags;
> -       if (dsi->dsc)
> +       if (dsi->dsc) {
>                 msm_host->dsc = dsi->dsc;
> +               msm_host->dsc_slice_per_pkt = dsi->dsc_slice_per_pkt;
> +               /* for backwards compatibility, assume 1 if not set */
> +               if (!msm_host->dsc_slice_per_pkt)
> +                       msm_host->dsc_slice_per_pkt = 1;
> +       }
>
>         ret = dsi_dev_attach(msm_host->pdev);
>         if (ret)
> diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
> index 0f520eeeaa8e3..1c1b56077d44a 100644
> --- a/include/drm/drm_mipi_dsi.h
> +++ b/include/drm/drm_mipi_dsi.h
> @@ -182,6 +182,7 @@ struct mipi_dsi_device_info {
>   * be set to the real limits of the hardware, zero is only accepted for
>   * legacy drivers
>   * @dsc: panel/bridge DSC pps payload to be sent
> + * @dsc_slice_per_pkt: number of DSC slices to be sent as in a single packet
>   */
>  struct mipi_dsi_device {
>         struct mipi_dsi_host *host;
> @@ -196,6 +197,7 @@ struct mipi_dsi_device {
>         unsigned long hs_rate;
>         unsigned long lp_rate;
>         struct drm_dsc_config *dsc;
> +       unsigned int dsc_slice_per_pkt;
>  };
>
>  /**
>
> --
> 2.34.1
>


-- 
With best wishes
Dmitry