linux-kernel - Re: [PATCH] drm/rockchip: use generic fbdev setup

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Message-ID: <20211101113415.3bed0f62.john@metanate.com>
Date:   Mon, 1 Nov 2021 11:34:15 +0000
From:   John Keeping <john@...anate.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>
Cc:     dri-devel@...ts.freedesktop.org, Sandy Huang <hjc@...k-chips.com>,
        Heiko Stübner <heiko@...ech.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH] drm/rockchip: use generic fbdev setup

On Sun, 31 Oct 2021 19:09:39 +0100
Thomas Zimmermann <tzimmermann@...e.de> wrote:
> Am 30.10.21 um 14:05 schrieb John Keeping:
> > On Fri, Oct 29, 2021 at 09:00:08PM +0200, Thomas Zimmermann wrote:  
> >> Am 29.10.21 um 13:50 schrieb John Keeping:  
> >>> The Rockchip fbdev code does not add anything compared to
> >>> drm_fbdev_generic_setup(); the one custom function for .fb_mmap does the
> >>> same thing as gem_prime_mmap which is called by the helper.
> >>>
> >>> Signed-off-by: John Keeping <john@...anate.com>
> >>> ---
> >>>    drivers/gpu/drm/rockchip/Makefile             |   1 -
> >>>    drivers/gpu/drm/rockchip/rockchip_drm_drv.c   |  10 +-
> >>>    drivers/gpu/drm/rockchip/rockchip_drm_drv.h   |   2 -
> >>>    drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c | 164 ------------------
> >>>    drivers/gpu/drm/rockchip/rockchip_drm_fbdev.h |  24 ---
> >>>    5 files changed, 2 insertions(+), 199 deletions(-)
> >>>    delete mode 100644 drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c
> >>>    delete mode 100644 drivers/gpu/drm/rockchip/rockchip_drm_fbdev.h
> >>>
> >>> diff --git a/drivers/gpu/drm/rockchip/Makefile b/drivers/gpu/drm/rockchip/Makefile
> >>> index 17a9e7eb2130..1a56f696558c 100644
> >>> --- a/drivers/gpu/drm/rockchip/Makefile
> >>> +++ b/drivers/gpu/drm/rockchip/Makefile
> >>> @@ -5,7 +5,6 @@
> >>>    rockchipdrm-y := rockchip_drm_drv.o rockchip_drm_fb.o \
> >>>    		rockchip_drm_gem.o rockchip_drm_vop.o rockchip_vop_reg.o
> >>> -rockchipdrm-$(CONFIG_DRM_FBDEV_EMULATION) += rockchip_drm_fbdev.o
> >>>    rockchipdrm-$(CONFIG_ROCKCHIP_ANALOGIX_DP) += analogix_dp-rockchip.o
> >>>    rockchipdrm-$(CONFIG_ROCKCHIP_CDN_DP) += cdn-dp-core.o cdn-dp-reg.o
> >>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> >>> index 69c699459dce..20d81ae69828 100644
> >>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> >>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> >>> @@ -26,7 +26,6 @@
> >>>    #include "rockchip_drm_drv.h"
> >>>    #include "rockchip_drm_fb.h"
> >>> -#include "rockchip_drm_fbdev.h"
> >>>    #include "rockchip_drm_gem.h"
> >>>    #define DRIVER_NAME	"rockchip"
> >>> @@ -159,10 +158,6 @@ static int rockchip_drm_bind(struct device *dev)
> >>>    	drm_mode_config_reset(drm_dev);
> >>> -	ret = rockchip_drm_fbdev_init(drm_dev);
> >>> -	if (ret)
> >>> -		goto err_unbind_all;
> >>> -
> >>>    	/* init kms poll for handling hpd */
> >>>    	drm_kms_helper_poll_init(drm_dev);
> >>> @@ -170,10 +165,11 @@ static int rockchip_drm_bind(struct device *dev)
> >>>    	if (ret)
> >>>    		goto err_kms_helper_poll_fini;
> >>> +	drm_fbdev_generic_setup(drm_dev, 32);  
> >>
> >> Please pass 0 for the final argument. The fbdev helpers pick 32 by default.
> >> Maybe leave a comment if you require 32 here.  
> > 
> > I wanted to minimise the changes introduced here - passing 32 matches
> > the value passed to drm_fb_helper_initial_config() in the deleted code
> > from rockchip_drm_fbdev.c.  
> 
> In that case
> 
> Acked-by: Thomas Zimmermann <tzimmermann@...e.de>

Thanks!

> > 
> > What do you think about changing this to 0 in a follow-up patch?
> >   
> 
> Yes. If possible, please provide a follow-up patch for this and set 
> modeconfig.prefered_depth to 24.

I'll follow up with a patch setting this to zero, but I'm not convinced
I understand mode_config.prefered_depth well enough to be confident
setting it to 24 is the right thing to do.

Looking at commits 23d4e55f7eeb ("drm/vkms: Unset preferred_depth") and
550f17441f53 ("drm/cirrus: flip default from 24bpp to 16bpp") it seems
that this will have a wider impact beyond fbdev.  32bpp has been used
since the Rockchip driver was added so I don't see any real need to
change to 24 now.


Regards,
John