linux-kernel - Re: [PATCH] drm/tidss: Soft Reset DISPC on startup

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Date:   Tue, 12 Apr 2022 14:40:55 +0530
From:   Devarsh Thakkar <devarsht@...com>
To:     <linux-kernel@...r.kernel.org>, <jyri.sarha@....fi>,
        <tomba@...nel.org>, <airlied@...ux.ie>, <daniel@...ll.ch>,
        <dri-devel@...ts.freedesktop.org>,
        <laurent.pinchart@...asonboard.com>,
        <tomi.valkeinen@...asonboard.com>
CC:     <nm@...com>, <a-bhatia1@...com>, <r-ravikumar@...com>,
        <nikhil.nd@...com>, <linux-arm-kernel@...ts.infradead.org>,
        <vigneshr@...com>
Subject: Re: [PATCH] drm/tidss: Soft Reset DISPC on startup

Hi Laurent, Tomi,

On 14/03/22 17:07, Devarsh Thakkar wrote:
> Soft reset the display subsystem controller on startup and wait for
> the reset to complete. This helps the scenario where display was
> already in use by some other core before the linux was booted.

Could you please help review this patch ?

Regards,

Devarsh

> Signed-off-by: Devarsh Thakkar <devarsht@...com>
> ---
>  drivers/gpu/drm/tidss/tidss_dispc.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c b/drivers/gpu/drm/tidss/tidss_dispc.c
> index 60b92df615aa..dae47853b728 100644
> --- a/drivers/gpu/drm/tidss/tidss_dispc.c
> +++ b/drivers/gpu/drm/tidss/tidss_dispc.c
> @@ -2650,6 +2650,20 @@ static void dispc_init_errata(struct dispc_device *dispc)
>  	}
>  }
>  
> +static void dispc_softreset(struct dispc_device *dispc)
> +{
> +	u32 val;
> +	int ret = 0;
> +
> +	/* Soft reset */
> +	REG_FLD_MOD(dispc, DSS_SYSCONFIG, 1, 1, 1);
> +	/* Wait for reset to complete */
> +	ret = readl_poll_timeout(dispc->base_common + DSS_SYSSTATUS,
> +				 val, val & 1, 100, 5000);
> +	if (ret)
> +		dev_warn(dispc->dev, "failed to reset dispc\n");
> +}
> +
>  int dispc_init(struct tidss_device *tidss)
>  {
>  	struct device *dev = tidss->dev;
> @@ -2709,6 +2723,10 @@ int dispc_init(struct tidss_device *tidss)
>  			return r;
>  	}
>  
> +	/* K2G display controller does not support soft reset */
> +	if (feat->subrev != DISPC_K2G)
> +		dispc_softreset(dispc);
> +
>  	for (i = 0; i < dispc->feat->num_vps; i++) {
>  		u32 gamma_size = dispc->feat->vp_feat.color.gamma_size;
>  		u32 *gamma_table;