linux-kernel - Re: [PATCH] drm: mxsfb: fix runtime PM handling

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Date:   Fri, 13 Jul 2018 11:03:15 +0200
From:   Marek Vasut <marex@...x.de>
To:     Anson Huang <Anson.Huang@....com>, airlied@...ux.ie,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     Linux-imx@....com
Subject: Re: [PATCH] drm: mxsfb: fix runtime PM handling

On 07/13/2018 10:54 AM, Anson Huang wrote:
> As display power domain is combined with lcdif node
> on some i.MX platforms like i.MX6SL, when lcdif driver
> is enabled, the mxsfb_load is called to enable runtime
> pm, and a pair of pm_runtime_get_sync and
> pm_runtime_put_sync are also called, that will cause
> generic power domain driver to disable lcdif power domain
> and lcdif is no longer working, the lcdif power
> should ONLY be turned off when display is disabled,
> so move the pm_runtime_put_sync to mxsfb_unload
> and remove the pm_runtime_get_sync in mxsfb_unload
> as well, in this way, when display is enabled, the
> lcdif power will be always ON until the display
> is disabled.
> 
> Signed-off-by: Anson Huang <Anson.Huang@....com>

Doesn't this also mean the block will always be on, thus wasting power ?

> ---
>  drivers/gpu/drm/mxsfb/mxsfb_drv.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> index ffe5137..1ba179b 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> @@ -235,7 +235,6 @@ static int mxsfb_load(struct drm_device *drm, unsigned long flags)
>  
>  	pm_runtime_get_sync(drm->dev);
>  	ret = drm_irq_install(drm, platform_get_irq(pdev, 0));
> -	pm_runtime_put_sync(drm->dev);
>  
>  	if (ret < 0) {
>  		dev_err(drm->dev, "Failed to install IRQ handler\n");
> @@ -264,6 +263,7 @@ static int mxsfb_load(struct drm_device *drm, unsigned long flags)
>  err_irq:
>  	drm_panel_detach(mxsfb->panel);
>  err_vblank:
> +	pm_runtime_put_sync(drm->dev);
>  	pm_runtime_disable(drm->dev);
>  
>  	return ret;
> @@ -279,7 +279,6 @@ static void mxsfb_unload(struct drm_device *drm)
>  	drm_kms_helper_poll_fini(drm);
>  	drm_mode_config_cleanup(drm);
>  
> -	pm_runtime_get_sync(drm->dev);
>  	drm_irq_uninstall(drm);
>  	pm_runtime_put_sync(drm->dev);
>  
> 


-- 
Best regards,
Marek Vasut