On Mon, Aug 30, 2021 at 02:08:14PM +0200, Noralf Trønnes wrote:
>
>
> Den 17.08.2021 15.56, skrev Daniel Vetter:
> > On Tue, Aug 17, 2021 at 02:29:12PM +0200, Noralf Trønnes wrote:
> >> Add XRGB8888 emulation support for devices that can only do RGB332.
> >>
> >> Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> >> Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
> >> ---
> >> drivers/gpu/drm/drm_format_helper.c | 47 +++++++++++++++++++++++++++++
> >> include/drm/drm_format_helper.h | 2 ++
> >> 2 files changed, 49 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
> >> index 5231104b1498..53b426da7467 100644
> >> --- a/drivers/gpu/drm/drm_format_helper.c
> >> +++ b/drivers/gpu/drm/drm_format_helper.c
> >> @@ -135,6 +135,53 @@ void drm_fb_swab(void *dst, void *src, struct drm_framebuffer *fb,
> >> }
> >> EXPORT_SYMBOL(drm_fb_swab);
> >>
> >> +static void drm_fb_xrgb8888_to_rgb332_line(u8 *dbuf, u32 *sbuf, unsigned int pixels)
> >> +{
> >> + unsigned int x;
> >> +
> >> + for (x = 0; x < pixels; x++)
> >> + dbuf[x] = ((sbuf[x] & 0x00e00000) >> 16) |
> >
> > I think for 2/3 bits correct rounding would be useful, not just masking.
> > i.e. before you shift add 0x00100000 here, and similar below.
> >
>
> Math isn't my strongest side and my brain failed to turn this into code.
Essentially add half of the lowest bit before you mask, so
((sbuf[x] + 0x10) & 0xe0 )
I dropped the shift to make it clear what's going on. If you're mask is
0xc0, then you simply add 0x20 before masking.
> > Also I just realized we've totally ignored endianess on these, which is
> > not great, because strictly speaking all the drm_fourcc codes should be
> > little endian. But I'm also not sure that's worth fixing ...
> >
>
> Is it as simple as using le32_to_cpu()?
I think so.
Plus on any format that has u16 output we'd need a cpu_to_le16 wrapped
around the entire thing.
-Daniel
> static void drm_fb_xrgb8888_to_rgb332_line(u8 *dbuf, __le32 *sbuf,
> unsigned int pixels)
> {
> unsigned int x;
> u32 pix;
>
> for (x = 0; x < pixels; x++) {
> pix = le32_to_cpu(sbuf[x]);
> dbuf[x] = ((pix & 0x00e00000) >> 16) |
> ((pix & 0x0000e000) >> 11) |
> ((pix & 0x000000c0) >> 6);
> }
> }
>
> Noralf.
>
> > Either way, lgtm:
> >
> > Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> >
> >> + ((sbuf[x] & 0x0000e000) >> 11) |
> >> + ((sbuf[x] & 0x000000c0) >> 6);
> >> +}
> >> +
> >> +/**
> >> + * drm_fb_xrgb8888_to_rgb332 - Convert XRGB8888 to RGB332 clip buffer
> >> + * @dst: RGB332 destination buffer
> >> + * @src: XRGB8888 source buffer
> >> + * @fb: DRM framebuffer
> >> + * @clip: Clip rectangle area to copy
> >> + *
> >> + * Drivers can use this function for RGB332 devices that don't natively support XRGB8888.
> >> + *
> >> + * This function does not apply clipping on dst, i.e. the destination is a small buffer
> >> + * containing the clip rect only.
> >> + */
> >> +void drm_fb_xrgb8888_to_rgb332(void *dst, void *src, struct drm_framebuffer *fb,
> >> + struct drm_rect *clip)
> >> +{
> >> + size_t width = drm_rect_width(clip);
> >> + size_t src_len = width * sizeof(u32);
> >> + unsigned int y;
> >> + void *sbuf;
> >> +
> >> + /* Use a buffer to speed up access on buffers with uncached read mapping (i.e. WC) */
> >> + sbuf = kmalloc(src_len, GFP_KERNEL);
> >> + if (!sbuf)
> >> + return;
> >> +
> >> + src += clip_offset(clip, fb->pitches[0], sizeof(u32));
> >> + for (y = 0; y < drm_rect_height(clip); y++) {
> >> + memcpy(sbuf, src, src_len);
> >> + drm_fb_xrgb8888_to_rgb332_line(dst, sbuf, width);
> >> + src += fb->pitches[0];
> >> + dst += width;
> >> + }
> >> +
> >> + kfree(sbuf);
> >> +}
> >> +EXPORT_SYMBOL(drm_fb_xrgb8888_to_rgb332);
> >> +
> >> static void drm_fb_xrgb8888_to_rgb565_line(u16 *dbuf, u32 *sbuf,
> >> unsigned int pixels,
> >> bool swab)
> >> diff --git a/include/drm/drm_format_helper.h b/include/drm/drm_format_helper.h
> >> index 4e0258a61311..d0809aff5cf8 100644
> >> --- a/include/drm/drm_format_helper.h
> >> +++ b/include/drm/drm_format_helper.h
> >> @@ -16,6 +16,8 @@ void drm_fb_memcpy_dstclip(void __iomem *dst, unsigned int dst_pitch, void *vadd
> >> struct drm_rect *clip);
> >> void drm_fb_swab(void *dst, void *src, struct drm_framebuffer *fb,
> >> struct drm_rect *clip, bool cached);
> >> +void drm_fb_xrgb8888_to_rgb332(void *dst, void *vaddr, struct drm_framebuffer *fb,
> >> + struct drm_rect *clip);
> >> void drm_fb_xrgb8888_to_rgb565(void *dst, void *vaddr,
> >> struct drm_framebuffer *fb,
> >> struct drm_rect *clip, bool swab);
> >> --
> >> 2.32.0
> >>
> >
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
