linux-kernel - Re: [PATCH v2] drm/msm/dsi: Enable BURST_MODE for command mode for DSI 6G v1.3+

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Date:   Tue, 11 Jul 2023 03:04:00 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Jessica Zhang <quic_jesszhan@...cinc.com>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     quic_abhinavk@...cinc.com, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/msm/dsi: Enable BURST_MODE for command mode for
 DSI 6G v1.3+

On 27/06/2023 23:31, Jessica Zhang wrote:
> During a frame transfer in command mode, there could be frequent
> LP11 <-> HS transitions when multiple DCS commands are sent mid-frame or
> if the DSI controller is running on slow clock and is throttled. To
> minimize frame latency due to these transitions, it is recommended to
> send the frame in a single burst.
> 
> This feature is supported for DSI 6G 1.3 and above, thus enable burst
> mode if supported.
> 
> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
> ---
> Changes in v2:
> - Moved MDP_CTRL2 register setting to dsi_ctrl_config() (Dmitry/Marijn)
> - Read previous value of MDP_CTRL2 register before writing to it
>    (Dmitry)
> - Link to v1: https://lore.kernel.org/r/20230608-b4-add-burst-mode-v1-1-55dfbcfada55@quicinc.com
> ---
>   drivers/gpu/drm/msm/dsi/dsi_host.c | 7 +++++++
>   1 file changed, 7 insertions(+)

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

> 
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index 3f6dfb4f9d5a..cdb404885f3c 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -752,6 +752,13 @@ static void dsi_ctrl_enable(struct msm_dsi_host *msm_host,
>   		/* Always insert DCS command */
>   		data |= DSI_CMD_CFG1_INSERT_DCS_COMMAND;
>   		dsi_write(msm_host, REG_DSI_CMD_CFG1, data);
> +
> +		if (msm_host->cfg_hnd->major == MSM_DSI_VER_MAJOR_6G &&
> +				msm_host->cfg_hnd->minor >= MSM_DSI_6G_VER_MINOR_V1_3) {

Nit: please intent in future to the same level (vim: "set cino=(0").

> +			data = dsi_read(msm_host, REG_DSI_CMD_MODE_MDP_CTRL2);
> +			data |= DSI_CMD_MODE_MDP_CTRL2_BURST_MODE;
> +			dsi_write(msm_host, REG_DSI_CMD_MODE_MDP_CTRL2, data);
> +		}
>   	}
>   
>   	dsi_write(msm_host, REG_DSI_CMD_DMA_CTRL,
> 
> ---
> base-commit: a0364260213c96f6817f7e85cdce293cb743460f
> change-id: 20230608-b4-add-burst-mode-a5bb144069fa
> 
> Best regards,

-- 
With best wishes
Dmitry