linux-kernel - Re: [PATCH 04/10] drm/tidss: Move reset to the end of dispc

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Date:   Wed, 1 Nov 2023 15:57:49 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc:     Aradhya Bhatia <a-bhatia1@...com>,
        Devarsh Thakkar <devarsht@...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>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/10] drm/tidss: Move reset to the end of dispc_init()

Hi Tomi,

Thank you for the patch.

On Wed, Nov 01, 2023 at 11:17:41AM +0200, Tomi Valkeinen wrote:
> We do a DSS reset in the middle of the dispc_init(). While that happens
> to work now, we should really make sure that e..g the fclk, which is
> acquired only later in the function, is enabled when doing a reset. This
> will be handled in a later patch, but for now, let's move the
> dispc_softreset() call to the end of dispc_init(), which is a sensible
> place for it anyway.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

But do I understand correctly that the device isn't powered up at this
point ? That seems problematic.

I'm also not sure why we need to reset the device at probe time.

> ---
>  drivers/gpu/drm/tidss/tidss_dispc.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c b/drivers/gpu/drm/tidss/tidss_dispc.c
> index ad7999434299..9430625e2d62 100644
> --- a/drivers/gpu/drm/tidss/tidss_dispc.c
> +++ b/drivers/gpu/drm/tidss/tidss_dispc.c
> @@ -2777,10 +2777,6 @@ 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;
> @@ -2831,5 +2827,9 @@ int dispc_init(struct tidss_device *tidss)
>  
>  	tidss->dispc = dispc;
>  
> +	/* K2G display controller does not support soft reset */
> +	if (feat->subrev != DISPC_K2G)
> +		dispc_softreset(dispc);
> +
>  	return 0;
>  }
> 

-- 
Regards,

Laurent Pinchart