[PATCH 1/9] drm/format-helper: Pass destination pitch to drm_fb_memcpy_dstclip()
Thomas Zimmermann
tzimmermann at suse.de
Mon Sep 28 09:13:06 UTC 2020
Hi
Am 28.09.20 um 10:53 schrieb Daniel Vetter:
> On Mon, Sep 28, 2020 at 9:22 AM Thomas Zimmermann <tzimmermann at suse.de> wrote:
>>
>> Hi
>>
>> Am 26.09.20 um 18:42 schrieb Daniel Vetter:
>>> On Fri, Sep 25, 2020 at 4:55 PM Thomas Zimmermann <tzimmermann at suse.de> wrote:
>>>>
>>>> Hi
>>>>
>>>> Am 29.06.20 um 10:40 schrieb Daniel Vetter:
>>>>> On Thu, Jun 25, 2020 at 02:00:03PM +0200, Thomas Zimmermann wrote:
>>>>>> The memcpy's destination buffer might have a different pitch than the
>>>>>> source. Support different pitches as function argument.
>>>>>>
>>>>>> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
>>>>>
>>>>> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>>>>>
>>>>> But I do have questions ... why did we allocate a source drm_framebuffer
>>>>> with mismatching pitch? That sounds backwards, especially for simplekms.
>>>>
>>>> There's userspace that allocates framebuffers in tiles of 64x64 pixels.
>>>> I think I've seen this with Gnome. So if you have a 800x600 display
>>>> mode, the allocated framebuffer has a scanline pitch of 832 pixels and
>>>> the final 32 pixels are ignored.
>>>
>>> At least with dumb buffer allocation ioctls userspace should not do
>>> that. If it wants 800x600, it needs to allocate 800x600, not something
>>
>> That ship has sailed.
>
> Not really, right now that ship is simply leaking and sinking. If we
> decide to patch this up from the kernel side, then indeed it has
> sailed. And I'm not sure that's a good idea.
We have code in at least cirrus, ast and mgag200 to support this. And
userspace has been behaving like this since at least when I got involved
(2017).
>
>>> else. The driver is supposed to apply any rounding necessary for the
>>> size. Or is this a buffer allocated somewhere else and then shared?
>>
>> I don't quite remember where exactly this was implemented. It was not a
>> shared buffer, though. IIRC the buffer allocation code in one of the
>> libs rounded the size towards multiples of 64. I remember thinking that
>> it was probably done for tiled rendering.
>
> Yeah, but you don't do rendering on dumb buffers. Like ever. So this
> smells like a userspace bug.
It's also part of the software rendering. It is not a bug, but
implemented deliberately in one of the userspace components that
allocates framebuffers (but I cannot remember which one.)
Best regards
Thomas
>
> If it's for shared buffers then I think that sounds more reasonable.
> -Daniel
>
>>
>> Best regards
>> Thomas
>>
>>> -Daniel
>>>
>>>> In regular drivers, we can handle this with the VGA offset register [1]
>>>> or some equivalent. That's obviously not an option with simplekms, so
>>>> the different pitch is required.
>>>>
>>>> Best regards
>>>> Thomas
>>>>
>>>> [1]
>>>> https://web.stanford.edu/class/cs140/projects/pintos/specs/freevga/vga/crtcreg.htm#13
>>>>
>>>>>
>>>>> Would be good to add the reasons why we need this to the commit message,
>>>>> I'm sure I'll discover it later on eventually.
>>>>> -Daniel
>>>>>
>>>>>> ---
>>>>>> drivers/gpu/drm/drm_format_helper.c | 9 +++++----
>>>>>> drivers/gpu/drm/mgag200/mgag200_mode.c | 2 +-
>>>>>> drivers/gpu/drm/tiny/cirrus.c | 2 +-
>>>>>> include/drm/drm_format_helper.h | 2 +-
>>>>>> 4 files changed, 8 insertions(+), 7 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
>>>>>> index c043ca364c86..8d5a683afea7 100644
>>>>>> --- a/drivers/gpu/drm/drm_format_helper.c
>>>>>> +++ b/drivers/gpu/drm/drm_format_helper.c
>>>>>> @@ -52,6 +52,7 @@ EXPORT_SYMBOL(drm_fb_memcpy);
>>>>>> /**
>>>>>> * drm_fb_memcpy_dstclip - Copy clip buffer
>>>>>> * @dst: Destination buffer (iomem)
>>>>>> + * @dst_pitch: Number of bytes between two consecutive scanlines within dst
>>>>>> * @vaddr: Source buffer
>>>>>> * @fb: DRM framebuffer
>>>>>> * @clip: Clip rectangle area to copy
>>>>>> @@ -59,12 +60,12 @@ EXPORT_SYMBOL(drm_fb_memcpy);
>>>>>> * This function applies clipping on dst, i.e. the destination is a
>>>>>> * full (iomem) framebuffer but only the clip rect content is copied over.
>>>>>> */
>>>>>> -void drm_fb_memcpy_dstclip(void __iomem *dst, void *vaddr,
>>>>>> - struct drm_framebuffer *fb,
>>>>>> +void drm_fb_memcpy_dstclip(void __iomem *dst, unsigned int dst_pitch,
>>>>>> + void *vaddr, struct drm_framebuffer *fb,
>>>>>> struct drm_rect *clip)
>>>>>> {
>>>>>> unsigned int cpp = fb->format->cpp[0];
>>>>>> - unsigned int offset = clip_offset(clip, fb->pitches[0], cpp);
>>>>>> + unsigned int offset = clip_offset(clip, dst_pitch, cpp);
>>>>>> size_t len = (clip->x2 - clip->x1) * cpp;
>>>>>> unsigned int y, lines = clip->y2 - clip->y1;
>>>>>>
>>>>>> @@ -73,7 +74,7 @@ void drm_fb_memcpy_dstclip(void __iomem *dst, void *vaddr,
>>>>>> for (y = 0; y < lines; y++) {
>>>>>> memcpy_toio(dst, vaddr, len);
>>>>>> vaddr += fb->pitches[0];
>>>>>> - dst += fb->pitches[0];
>>>>>> + dst += dst_pitch;
>>>>>> }
>>>>>> }
>>>>>> EXPORT_SYMBOL(drm_fb_memcpy_dstclip);
>>>>>> diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
>>>>>> index f16bd278ab7e..7d4f3a62d885 100644
>>>>>> --- a/drivers/gpu/drm/mgag200/mgag200_mode.c
>>>>>> +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
>>>>>> @@ -1586,7 +1586,7 @@ mgag200_handle_damage(struct mga_device *mdev, struct drm_framebuffer *fb,
>>>>>> if (drm_WARN_ON(dev, !vmap))
>>>>>> return; /* BUG: SHMEM BO should always be vmapped */
>>>>>>
>>>>>> - drm_fb_memcpy_dstclip(mdev->vram, vmap, fb, clip);
>>>>>> + drm_fb_memcpy_dstclip(mdev->vram, fb->pitches[0], vmap, fb, clip);
>>>>>>
>>>>>> drm_gem_shmem_vunmap(fb->obj[0], vmap);
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/tiny/cirrus.c b/drivers/gpu/drm/tiny/cirrus.c
>>>>>> index 744a8e337e41..2dd9e5e31e3d 100644
>>>>>> --- a/drivers/gpu/drm/tiny/cirrus.c
>>>>>> +++ b/drivers/gpu/drm/tiny/cirrus.c
>>>>>> @@ -327,7 +327,7 @@ static int cirrus_fb_blit_rect(struct drm_framebuffer *fb,
>>>>>> goto out_dev_exit;
>>>>>>
>>>>>> if (cirrus->cpp == fb->format->cpp[0])
>>>>>> - drm_fb_memcpy_dstclip(cirrus->vram,
>>>>>> + drm_fb_memcpy_dstclip(cirrus->vram, fb->pitches[0],
>>>>>> vmap, fb, rect);
>>>>>>
>>>>>> else if (fb->format->cpp[0] == 4 && cirrus->cpp == 2)
>>>>>> diff --git a/include/drm/drm_format_helper.h b/include/drm/drm_format_helper.h
>>>>>> index 5f9e37032468..2b5036a5fbe7 100644
>>>>>> --- a/include/drm/drm_format_helper.h
>>>>>> +++ b/include/drm/drm_format_helper.h
>>>>>> @@ -11,7 +11,7 @@ struct drm_rect;
>>>>>>
>>>>>> void drm_fb_memcpy(void *dst, void *vaddr, struct drm_framebuffer *fb,
>>>>>> struct drm_rect *clip);
>>>>>> -void drm_fb_memcpy_dstclip(void __iomem *dst, void *vaddr,
>>>>>> +void drm_fb_memcpy_dstclip(void __iomem *dst, unsigned int dst_pitch, void *vaddr,
>>>>>> struct drm_framebuffer *fb,
>>>>>> struct drm_rect *clip);
>>>>>> void drm_fb_swab(void *dst, void *src, struct drm_framebuffer *fb,
>>>>>> --
>>>>>> 2.27.0
>>>>>>
>>>>>
>>>>
>>>> --
>>>> Thomas Zimmermann
>>>> Graphics Driver Developer
>>>> SUSE Software Solutions Germany GmbH
>>>> Maxfeldstr. 5, 90409 Nürnberg, Germany
>>>> (HRB 36809, AG Nürnberg)
>>>> Geschäftsführer: Felix Imendörffer
>>>>
>>>
>>>
>>
>> --
>> Thomas Zimmermann
>> Graphics Driver Developer
>> SUSE Software Solutions Germany GmbH
>> Maxfeldstr. 5, 90409 Nürnberg, Germany
>> (HRB 36809, AG Nürnberg)
>> Geschäftsführer: Felix Imendörffer
>>
>
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
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