linux-kernel - Re: [PATCH v2 10/18] drm/bridge: cdns-dsi: Fix event mode

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Message-ID: <eb4729f4-2f1b-49ca-ab01-4afca321e4a1@ti.com>
Date: Fri, 11 Apr 2025 16:34:38 +0530
From: Jayesh Choudhary <j-choudhary@...com>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
        Jyri Sarha
	<jyri.sarha@....fi>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Vinod Koul
	<vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Andrzej Hajda
	<andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert
 Foss <rfoss@...nel.org>,
        Laurent Pinchart
	<Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej
 Skrabec <jernej.skrabec@...il.com>
CC: <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        <linux-phy@...ts.infradead.org>,
        Francesco Dolcini <francesco@...cini.it>,
        Aradhya Bhatia <aradhya.bhatia@...ux.dev>,
        Devarsh Thakkar <devarsht@...com>
Subject: Re: [PATCH v2 10/18] drm/bridge: cdns-dsi: Fix event mode

Hello Tomi,

On 02/04/25 19:00, Tomi Valkeinen wrote:
> The timings calculation gets it wrong for DSI event mode, resulting in
> too large hbp value. Fix the issue by taking into account the
> pulse/event mode difference.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>

Reviewed-by: Jayesh Choudhary <j-choudhary@...com>

> ---
>   drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c | 33 ++++++++++++++++++--------
>   1 file changed, 23 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> index 62811631341b..9797e6faa29d 100644
> --- a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> +++ b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> @@ -417,7 +417,8 @@
>   #define DSI_OUTPUT_PORT			0
>   #define DSI_INPUT_PORT(inputid)		(1 + (inputid))
>   
> -#define DSI_HBP_FRAME_OVERHEAD		12
> +#define DSI_HBP_FRAME_PULSE_OVERHEAD	12
> +#define DSI_HBP_FRAME_EVENT_OVERHEAD	16


I have also observed this 4B discrepancy for event-mode after comparing
the dsi packet sizes for each line type as per the dsi specifications.

>   #define DSI_HSA_FRAME_OVERHEAD		14
>   #define DSI_HFP_FRAME_OVERHEAD		6
>   #define DSI_HSS_VSS_VSE_FRAME_OVERHEAD	4
> @@ -503,12 +504,18 @@ static int cdns_dsi_mode2cfg(struct cdns_dsi *dsi,
>   
>   	bpp = mipi_dsi_pixel_format_to_bpp(output->dev->format);
>   
> -	dsi_cfg->hbp = dpi_to_dsi_timing(dpi_hbp + (sync_pulse ? 0 : dpi_hsa),
> -					 bpp, DSI_HBP_FRAME_OVERHEAD);
> +	if (sync_pulse) {
> +		dsi_cfg->hbp = dpi_to_dsi_timing(dpi_hbp, bpp,
> +						 DSI_HBP_FRAME_PULSE_OVERHEAD);
>   
> -	if (sync_pulse)
> -		dsi_cfg->hsa =
> -			dpi_to_dsi_timing(dpi_hsa, bpp, DSI_HSA_FRAME_OVERHEAD);
> +		dsi_cfg->hsa = dpi_to_dsi_timing(dpi_hsa, bpp,
> +						 DSI_HSA_FRAME_OVERHEAD);
> +	} else {
> +		dsi_cfg->hbp = dpi_to_dsi_timing(dpi_hbp + dpi_hsa, bpp,
> +						 DSI_HBP_FRAME_EVENT_OVERHEAD);
> +
> +		dsi_cfg->hsa = 0;
> +	}
>   
>   	dsi_cfg->hact = dpi_to_dsi_timing(dpi_hact, bpp, 0);
>   
> @@ -532,9 +539,12 @@ static int cdns_dsi_adjust_phy_config(struct cdns_dsi *dsi,
>   	unsigned int dsi_hfp_ext;
>   	unsigned int lanes = output->dev->lanes;
>   
> -	dsi_htotal = dsi_cfg->hbp + DSI_HBP_FRAME_OVERHEAD;
> -	if (output->dev->mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE)
> +	if (output->dev->mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE) {
> +		dsi_htotal = dsi_cfg->hbp + DSI_HBP_FRAME_PULSE_OVERHEAD;
>   		dsi_htotal += dsi_cfg->hsa + DSI_HSA_FRAME_OVERHEAD;
> +	} else {
> +		dsi_htotal = dsi_cfg->hbp + DSI_HBP_FRAME_EVENT_OVERHEAD;
> +	}
>   
>   	dsi_htotal += dsi_cfg->hact;
>   	dsi_htotal += dsi_cfg->hfp + DSI_HFP_FRAME_OVERHEAD;
> @@ -607,9 +617,12 @@ static int cdns_dsi_check_conf(struct cdns_dsi *dsi,
>   		return -EINVAL;
>   	}
>   
> -	dsi_hss_hsa_hse_hbp = dsi_cfg->hbp + DSI_HBP_FRAME_OVERHEAD;
> -	if (output->dev->mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE)
> +	if (output->dev->mode_flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE) {
> +		dsi_hss_hsa_hse_hbp = dsi_cfg->hbp + DSI_HBP_FRAME_PULSE_OVERHEAD;
>   		dsi_hss_hsa_hse_hbp += dsi_cfg->hsa + DSI_HSA_FRAME_OVERHEAD;
> +	} else {
> +		dsi_hss_hsa_hse_hbp = dsi_cfg->hbp + DSI_HBP_FRAME_EVENT_OVERHEAD;
> +	}
>   
>   	/*
>   	 * Make sure DPI(HFP) > DSI(HSS+HSA+HSE+HBP) to guarantee that the FIFO
> 

Thanks,
Jayesh