linux-kernel - Re: [PATCH 08/10] drm/tidss: Add dispc_is

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Message-ID: <20231101143231.GX12764@pendragon.ideasonboard.com>
Date:   Wed, 1 Nov 2023 16:32:31 +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 08/10] drm/tidss: Add dispc_is_idle()

Hi Tomi,

Thank you for the patch.

On Wed, Nov 01, 2023 at 11:17:45AM +0200, Tomi Valkeinen wrote:
> Add a helper function, dispc_is_idle(), which returns whether the DSS is
> idle (i.e. is any video port enabled).
> 
> For now we add a call to it in the suspend and resume callbacks, and
> print a warning if in either place the DSS is not idle.

Could you please explain here why these checks are needed/useful ? Why
would the dispc not be idle ?

> In the future
> this can be used to detect if the bootloader had enabled the DSS, and
> the driver can act on that.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> ---
>  drivers/gpu/drm/tidss/tidss_dispc.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c b/drivers/gpu/drm/tidss/tidss_dispc.c
> index 13db062892e3..a527c28c8833 100644
> --- a/drivers/gpu/drm/tidss/tidss_dispc.c
> +++ b/drivers/gpu/drm/tidss/tidss_dispc.c
> @@ -2603,10 +2603,18 @@ void dispc_vp_setup(struct dispc_device *dispc, u32 hw_videoport,
>  	dispc_vp_set_color_mgmt(dispc, hw_videoport, state, newmodeset);
>  }
>  
> +static bool dispc_is_idle(struct dispc_device *dispc)
> +{
> +	return REG_GET(dispc, DSS_SYSSTATUS, 9, 9);
> +}
> +
>  int dispc_runtime_suspend(struct dispc_device *dispc)
>  {
>  	dev_dbg(dispc->dev, "suspend\n");
>  
> +	if (!dispc_is_idle(dispc))
> +		dev_warn(dispc->dev, "Bad HW state: DSS not idle when suspending");
> +
>  	dispc->is_enabled = false;
>  
>  	clk_disable_unprepare(dispc->fclk);
> @@ -2620,6 +2628,9 @@ int dispc_runtime_resume(struct dispc_device *dispc)
>  
>  	clk_prepare_enable(dispc->fclk);
>  
> +	if (!dispc_is_idle(dispc))
> +		dev_warn(dispc->dev, "Bad HW state: DSS not idle when resuming");
> +
>  	if (REG_GET(dispc, DSS_SYSSTATUS, 0, 0) == 0)
>  		dev_warn(dispc->dev, "DSS FUNC RESET not done!\n");
>  

-- 
Regards,

Laurent Pinchart