linux-kernel - Re: [PATCH] drm/imx: Remove unused field imx_drm

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Date:   Tue, 17 Jul 2018 14:34:32 +0000
From:   Leonard Crestez <leonard.crestez@....com>
To:     "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "stefan@...er.ch" <stefan@...er.ch>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>
CC:     dl-linux-imx <linux-imx@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "laurent.pinchart+renesas@...asonboard.com" 
        <laurent.pinchart+renesas@...asonboard.com>,
        "Liviu.Dudau@....com" <Liviu.Dudau@....com>,
        Fabio Estevam <fabio.estevam@....com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "gnuiyl@...il.com" <gnuiyl@...il.com>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>
Subject: Re: [PATCH] drm/imx: Remove unused field imx_drm_device.pipes

On Tue, 2018-07-17 at 15:21 +0200, Philipp Zabel wrote:
> On Tue, 2018-07-17 at 15:11 +0300, Leonard Crestez wrote:
> > This has been unused since commit 44b460cfe554 ("drm: imx: remove struct
> > imx_drm_crtc and imx_drm_crtc_helper_funcs")
> > 
> > Signed-off-by: Leonard Crestez <leonard.crestez@....com>
> 
> Applied to imx-drm/next, thank you.
> 
> > ---
> >  drivers/gpu/drm/imx/imx-drm-core.c | 1 -
> >  1 file changed, 1 deletion(-)
> > 
> > Looking at the imx_drm_device struct it is only used to save the
> > drm_atomic_helper_suspend state. It seems like this could be replaced
> > with drm_mode_config_helper_suspend/resume and the entire struct
> > removed.
> > 
> > The only difference between imx_drm_suspend/resume and
> > drm_mode_config_helper_suspend/resume is that the latter also suspends
> > the fb_helper. This would be an improvement, right?
> 
> This looks about right to me. We currently don't call the
> fbdev suspend/resume notifiers at all. The correct call
> would be drm_fbdev_cma_set_suspend_unlocked instead of
> drm_fb_helper_set_suspend_unlocked, though.
> 
> Since drm_fb_cma_fbdev_init registers its fb_helper with the
> drm_device via drm_fb_helper_init, both (currently) do exactly
> the same thing.

Is drm_fbdev_cma_set_suspend expected to ever do anything extra on top
of drm_fb_helper_set_suspend? Since it only handles memory management
my answer would be "no".

Grepping for drm_fbdev_cma_set_suspend I only find two users: rcar-du
and hdlcd. The suspend/resume code in both of those drivers looks
entirely equivalent to drm_mode_config_helper_suspend/resume.

So maybe drm_fbdev_cma_set_suspend itself should be dropped in favor of
drm_mode_config_helper_suspend everywhere.