linux-kernel - Re: [PATCH v5 0/3] Add option to mmap GEM buffers cached

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Date:   Sun, 23 May 2021 20:19:27 +0100
From:   Paul Cercueil <paul@...pouillou.net>
To:     Thomas Zimmermann <tzimmermann@...e.de>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-mips@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>, list@...ndingux.net
Subject: Re: [PATCH v5 0/3] Add option to mmap GEM buffers cached

Hi Thomas,

Le dim., mai 23 2021 at 21:05:30 +0200, Thomas Zimmermann 
<tzimmermann@...e.de> a écrit :
> Hi
> 
> Am 23.05.21 um 19:04 schrieb Paul Cercueil:
>> V5 of my patchset which adds the option for having GEM buffers 
>> backed by
>> non-coherent memory.
>> 
>> Changes from V4:
>> 
>> - [2/3]:
>>      - Rename to drm_fb_cma_sync_non_coherent
>>      - Invert loops for better cache locality
>>      - Only sync BOs that have the non-coherent flag
>>      - Properly sort includes
>>      - Move to drm_fb_cma_helper.c to avoid circular dependency
> 
> I'm pretty sure it's still not the right place. That would be 
> something like drm_gem_cma_atomic_helper.c, but creating a new file 
> just for a single function doesn't make sense.

drm_fb_cma_sync_non_coherent calls drm_fb_cma_* functions, so it's a 
better match than its former location (which wasn't good as it created 
a circular dependency between drm.ko and drm-kms-helper.ko).

Do you have a better idea?

>> 
>> - [3/3]:
>>      - Fix drm_atomic_get_new_plane_state() used to retrieve the old
>>        state
>>      - Use custom drm_gem_fb_create()
> 
> It's often a better choice to express such differences via different 
> data structures (i.e., different instances of drm_mode_config_funcs) 
> but it's not a big deal either.

The different drm_mode_config_funcs instances already exist in 
drm_gem_framebuffer_helper.c but are static, and drm_gem_fb_create() 
and drm_gem_fb_create_with_dirty() are just tiny wrappers around 
drm_gem_fb_create_with_funcs() with the corresponding 
drm_mode_config_funcs instance. I didn't want to copy them to 
ingenic-drm-drv.c, but maybe I can export the symbols and use 
drm_gem_fb_create_with_funcs() directly?

> Please go ahaed and merge if no one objects. All patches:
> 
> Acked-by: Thomas Zimmermann <tzimmermann@...e.de>

Thanks!

Cheers,
-Paul

> Best regards
> Thomas
> 
>>      - Only check damage clips and sync DMA buffers if non-coherent
>>        buffers are used
>> 
>> Cheers,
>> -Paul
>> 
>> Paul Cercueil (3):
>>    drm: Add support for GEM buffers backed by non-coherent memory
>>    drm: Add and export function drm_fb_cma_sync_non_coherent
>>    drm/ingenic: Add option to alloc cached GEM buffers
>> 
>>   drivers/gpu/drm/drm_fb_cma_helper.c       | 46 ++++++++++++++++++
>>   drivers/gpu/drm/drm_gem_cma_helper.c      | 38 +++++++++++----
>>   drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 59 
>> +++++++++++++++++++++--
>>   drivers/gpu/drm/ingenic/ingenic-drm.h     |  1 +
>>   drivers/gpu/drm/ingenic/ingenic-ipu.c     | 21 ++++++--
>>   include/drm/drm_fb_cma_helper.h           |  4 ++
>>   include/drm/drm_gem_cma_helper.h          |  3 ++
>>   7 files changed, 156 insertions(+), 16 deletions(-)
>> 
> 
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Felix Imendörffer
>