linux-kernel - Re: [EXTERNAL] [PATCH 3/7] drm/bridge: cdns-dsi: Wait for Clk and Data Lanes to be ready

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Message-ID: <f45daf0d6c0ab8a225277621b6e6b373929d145a.camel@phytec.de>
Date: Wed, 22 May 2024 10:23:37 +0000
From: Dominik Haller <D.Haller@...tec.de>
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Subject: Re: [EXTERNAL] [PATCH 3/7] drm/bridge: cdns-dsi: Wait for Clk and
 Data Lanes to be ready

Hi Aradhya,

this fixes the color-shift bug on our setup:
j721s2 -> ti,sn65dsi83 -> edt,etml1010g3dra



Tested-by: Dominik Haller <d.haller@...tec.de>


On Sat, 2024-05-11 at 21:00 +0530, Aradhya Bhatia wrote:
> Once the DSI Link and DSI Phy are initialized, the code needs to wait
> for Clk and Data Lanes to be ready, before continuing configuration.
> This is in accordance with the DSI Start-up procedure, found in the
> Technical Reference Manual of Texas Instrument's J721E SoC[0] which
> houses this DSI TX controller.
> 
> If the previous bridge (or crtc/encoder) are configured pre-maturely,
> the input signal FIFO gets corrupt. This introduces a color-shift on
> the
> display.
> 
> Allow the driver to wait for the clk and data lanes to get ready
> during
> DSI enable.
> 
> Fixes: e19233955d9e ("drm/bridge: Add Cadence DSI driver")
> Signed-off-by: Aradhya Bhatia <a-bhatia1@...com>
> ---
>  drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> index 557b037bbc67..05d2f4cc50da 100644
> --- a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> +++ b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> @@ -761,7 +761,7 @@ static void cdns_dsi_bridge_enable(struct
> drm_bridge *bridge)
>  	struct phy_configure_opts_mipi_dphy *phy_cfg = &output-
> >phy_opts.mipi_dphy;
>  	unsigned long tx_byte_period;
>  	struct cdns_dsi_cfg dsi_cfg;
> -	u32 tmp, reg_wakeup, div;
> +	u32 tmp, reg_wakeup, div, status;
>  	int nlanes;
>  
>  	if (WARN_ON(pm_runtime_get_sync(dsi->base.dev) < 0))
> @@ -778,6 +778,17 @@ static void cdns_dsi_bridge_enable(struct
> drm_bridge *bridge)
>  	cdns_dsi_init_link(dsi);
>  	cdns_dsi_hs_init(dsi);
>  
> +	/*
> +	 * Now that the DSI Link and DSI Phy are initialized,
> +	 * wait for the CLK and Data Lanes to be ready.
> +	 */
> +	tmp = CLK_LANE_RDY;
> +	for (int i = 0; i < nlanes; i++)
> +		tmp |= DATA_LANE_RDY(i);
> +
> +	WARN_ON_ONCE(readl_poll_timeout(dsi->regs + MCTL_MAIN_STS,
> status,
> +					status & tmp, 100, 0));
> +
>  	writel(HBP_LEN(dsi_cfg.hbp) | HSA_LEN(dsi_cfg.hsa),
>  	       dsi->regs + VID_HSIZE1);
>  	writel(HFP_LEN(dsi_cfg.hfp) | HACT_LEN(dsi_cfg.hact),