linux-kernel - Re: [PATCH 3/3] drm/msm/dsi: Enable DATABUS

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Message-ID: <3a6cc492-6b54-2c70-402e-995c0b003c01@linaro.org>
Date:   Wed, 14 Jun 2023 10:49:31 +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>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Marijn Suijten <marijn.suijten@...ainline.org>
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 3/3] drm/msm/dsi: Enable DATABUS_WIDEN for DSI command
 mode

On 14/06/2023 04:57, Jessica Zhang wrote:
> DSI 6G v2.5.x+ supports a data-bus widen mode that allows DSI to send
> 48 bits of compressed data per pclk instead of 24.
> 
> For all chipsets that support this mode, enable it whenever DSC is
> enabled as recommend by the hardware programming guide.
> 
> Only enable this for command mode as we are currently unable to validate
> it for video mode.
> 
> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
> ---
> 
> Note: The dsi.xml.h changes were generated using the headergen2 script in
> envytools [1], but the changes to the copyright and rules-ng-ng source file
> paths were dropped.
> 
> [1] https://github.com/freedreno/envytools/
> 
>   drivers/gpu/drm/msm/dsi/dsi.xml.h  |  1 +
>   drivers/gpu/drm/msm/dsi/dsi_host.c | 19 ++++++++++++++++++-
>   2 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/dsi.xml.h b/drivers/gpu/drm/msm/dsi/dsi.xml.h
> index a4a154601114..2a7d980e12c3 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi.xml.h
> +++ b/drivers/gpu/drm/msm/dsi/dsi.xml.h
> @@ -664,6 +664,7 @@ static inline uint32_t DSI_CMD_MODE_MDP_CTRL2_INPUT_RGB_SWAP(enum dsi_rgb_swap v
>   	return ((val) << DSI_CMD_MODE_MDP_CTRL2_INPUT_RGB_SWAP__SHIFT) & DSI_CMD_MODE_MDP_CTRL2_INPUT_RGB_SWAP__MASK;
>   }
>   #define DSI_CMD_MODE_MDP_CTRL2_BURST_MODE			0x00010000
> +#define DSI_CMD_MODE_MDP_CTRL2_DATABUS_WIDEN			0x00100000
> 
>   #define REG_DSI_CMD_MODE_MDP_STREAM2_CTRL			0x000001b8
>   #define DSI_CMD_MODE_MDP_STREAM2_CTRL_DATA_TYPE__MASK		0x0000003f
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index 5d7b4409e4e9..1da5238e7105 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -927,6 +927,9 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
>   	u32 hdisplay = mode->hdisplay;
>   	u32 wc;
>   	int ret;
> +	bool widebus_supported = msm_host->cfg_hnd->major == MSM_DSI_VER_MAJOR_6G &&
> +			msm_host->cfg_hnd->minor >= MSM_DSI_6G_VER_MINOR_V2_5_0;
> +
> 
>   	DBG("");
> 
> @@ -973,8 +976,15 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
>   		 *
>   		 * hdisplay will be divided by 3 here to account for the fact
>   		 * that DPU sends 3 bytes per pclk cycle to DSI.
> +		 *
> +		 * If widebus is supported, set DATABUS_WIDEN register and divide hdisplay by 6
> +		 * instead of 3

This is useless, it is already obvious from the code below. Instead 
there should be something like "wide bus extends that to 6 bytes per 
pclk cycle"

>   		 */
> -		hdisplay = DIV_ROUND_UP(msm_dsc_get_bytes_per_line(msm_host->dsc), 3);
> +		if (!(msm_host->mode_flags & MIPI_DSI_MODE_VIDEO) && widebus_supported)
> +			hdisplay = DIV_ROUND_UP(msm_dsc_get_bytes_per_line(msm_host->dsc), 6);
> +		else
> +			hdisplay = DIV_ROUND_UP(msm_dsc_get_bytes_per_line(msm_host->dsc), 3);
> +
>   		h_total += hdisplay;
>   		ha_end = ha_start + hdisplay;
>   	}
> @@ -1027,6 +1037,13 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
>   		dsi_write(msm_host, REG_DSI_CMD_MDP_STREAM0_TOTAL,
>   			DSI_CMD_MDP_STREAM0_TOTAL_H_TOTAL(hdisplay) |
>   			DSI_CMD_MDP_STREAM0_TOTAL_V_TOTAL(mode->vdisplay));
> +
> +		if (msm_host->dsc && widebus_supported) {
> +			u32 mdp_ctrl2 = dsi_read(msm_host, REG_DSI_CMD_MODE_MDP_CTRL2);
> +
> +			mdp_ctrl2 |= DSI_CMD_MODE_MDP_CTRL2_DATABUS_WIDEN;
> +			dsi_write(msm_host, REG_DSI_CMD_MODE_MDP_CTRL2, mdp_ctrl2);

Is widebus applicable only to the CMD mode, or video mode can employ it too?

> +		}
>   	}
>   }
> 
> 
> --
> 2.40.1
> 

-- 
With best wishes
Dmitry