Hi Pekka,
On 10/18/21 5:30 AM, Pekka Paalanen wrote:
On Tue, 5 Oct 2021 17:16:37 -0300
Igor Matheus Andrade Torrente <igormtorrente@xxxxxxxxx> wrote:
Currently the blend function only accepts XRGB_8888 and ARGB_8888
as a color input.
This patch refactors all the functions related to the plane composition
to overcome this limitation.
Now the blend function receives a format handler to each plane and a
blend function pointer. It will take two ARGB_1616161616 pixels, one
for each handler, and will use the blend function to calculate and
store the final color in the output buffer.
These format handlers will receive the `vkms_composer` and a pair of
coordinates. And they should return the respective pixel in the
ARGB_16161616 format.
The blend function will receive two ARGB_16161616 pixels, x, y, and
the vkms_composer of the output buffer. The method should perform the
blend operation and store output to the format aforementioned
ARGB_16161616.
Hi,
here are some drive-by comments which you are free to take or leave.
To find more efficient ways to do this, you might want research Pixman
library. It's MIT licensed.
IIRC, the elementary operations there operate on pixel lines (pointer +
length), not individual pixels (image, x, y). Input conversion function
reads and converts a whole line a time. Blending function blends two
lines and writes the output into back one of the lines. Output
conversion function takes a line and converts it into destination
buffer. That way the elementary operations do not need to take stride
into account, and blending does not need to deal with varying memory
alignment FWIW. The inner loops involve much less function calls and
state, probably.
I was doing some rudimentary profiling, and I noticed that the code
spends most of the time with the indirect system call overhead and not
the actual computation. This can definitively help with it.
Pixman may not do exactly this, but it does something very similar.
Pixman also has multiple different levels of optimisations, which may
not be necessary for VKMS.
It's a trade-off between speed and temporary memory consumed. You need
temporary buffers for two lines, but not more (not a whole image in
full intermediate precision). Further optimisation could determine
whether to process whole image rows as lines, or split a row into
multiple lines to stay within CPU cache size.
Sorry, I didn't understand the idea of the last sentence.
Since it seems you are blending multiple planes into a single
destination which is assumed to be opaque, you might also be able to do
the multiple blends without convert-writing and read-converting to/from
the destination between every plane. I think that might be possible to
architect on top of the per-line operations still.
I tried it. But I don't know how to do this without looking like a mess.
Does the pixman perform some similar?
Signed-off-by: Igor Matheus Andrade Torrente <igormtorrente@xxxxxxxxx>
---
drivers/gpu/drm/vkms/vkms_composer.c | 275 ++++++++++++++-------------
drivers/gpu/drm/vkms/vkms_formats.h | 125 ++++++++++++
2 files changed, 271 insertions(+), 129 deletions(-)
create mode 100644 drivers/gpu/drm/vkms/vkms_formats.h
...
+
+u64 ARGB8888_to_ARGB16161616(struct vkms_composer *composer, int x, int y)
+{
+ u8 *pixel_addr = packed_pixels_addr(composer, x, y);
+
+ /*
+ * Organizes the channels in their respective positions and converts
+ * the 8 bits channel to 16.
+ * The 257 is the "conversion ratio". This number is obtained by the
+ * (2^16 - 1) / (2^8 - 1) division. Which, in this case, tries to get
+ * the best color value in a color space with more possibilities.
Pixel format, not color space. >
+ * And a similar idea applies to others RGB color conversions.
+ */
+ return ((u64)pixel_addr[3] * 257) << 48 |
+ ((u64)pixel_addr[2] * 257) << 32 |
+ ((u64)pixel_addr[1] * 257) << 16 |
+ ((u64)pixel_addr[0] * 257);
I wonder if the compiler is smart enough to choose between "mul 257"
and "(v << 8) | v" operations... but that's probably totally drowning
under the overhead of per (x,y) looping.
I disassembled the code to check it. And looks like the compiler is
replacing the multiplication with shifts and additions.
ARGB8888_to_ARGB16161616:
0xffffffff816ad660 <+0>: imul 0x12c(%rdi),%edx
0xffffffff816ad667 <+7>: imul 0x130(%rdi),%esi
0xffffffff816ad66e <+14>: add %edx,%esi
0xffffffff816ad670 <+16>: add 0x128(%rdi),%esi
0xffffffff816ad676 <+22>: movslq %esi,%rax
0xffffffff816ad679 <+25>: add 0xe8(%rdi),%rax
0xffffffff816ad680 <+32>: movzbl 0x3(%rax),%ecx
0xffffffff816ad684 <+36>: movzbl 0x2(%rax),%esi
0xffffffff816ad688 <+40>: mov %rcx,%rdx
0xffffffff816ad68b <+43>: shl $0x8,%rdx
0xffffffff816ad68f <+47>: add %rcx,%rdx
0xffffffff816ad692 <+50>: mov %rsi,%rcx
0xffffffff816ad695 <+53>: shl $0x8,%rcx
0xffffffff816ad699 <+57>: shl $0x30,%rdx
0xffffffff816ad69d <+61>: add %rsi,%rcx
0xffffffff816ad6a0 <+64>: movzbl (%rax),%esi
0xffffffff816ad6a3 <+67>: shl $0x20,%rcx
0xffffffff816ad6a7 <+71>: or %rcx,%rdx
0xffffffff816ad6aa <+74>: mov %rsi,%rcx
0xffffffff816ad6ad <+77>: shl $0x8,%rcx
0xffffffff816ad6b1 <+81>: add %rsi,%rcx
0xffffffff816ad6b4 <+84>: or %rcx,%rdx
0xffffffff816ad6b7 <+87>: movzbl 0x1(%rax),%ecx
0xffffffff816ad6bb <+91>: mov %rcx,%rax
0xffffffff816ad6be <+94>: shl $0x8,%rax
0xffffffff816ad6c2 <+98>: add %rcx,%rax
0xffffffff816ad6c5 <+101>: shl $0x10,%rax
0xffffffff816ad6c9 <+105>: or %rdx,%rax
0xffffffff816ad6cc <+108>: ret
+}
+
+u64 XRGB8888_to_ARGB16161616(struct vkms_composer *composer, int x, int y)
+{
+ u8 *pixel_addr = packed_pixels_addr(composer, x, y);
+
+ /*
+ * The same as the ARGB8888 but with the alpha channel as the
+ * maximum value as possible.
+ */
+ return 0xffffllu << 48 |
+ ((u64)pixel_addr[2] * 257) << 32 |
+ ((u64)pixel_addr[1] * 257) << 16 |
+ ((u64)pixel_addr[0] * 257);
+}
+
+u64 get_ARGB16161616(struct vkms_composer *composer, int x, int y)
+{
+ __le64 *pixel_addr = packed_pixels_addr(composer, x, y);
+
+ /*
+ * Because the format byte order is in little-endian and this code
+ * needs to run on big-endian machines too, we need modify
+ * the byte order from little-endian to the CPU native byte order.
+ */
+ return le64_to_cpu(*pixel_addr);
+}
+
+/*
+ * The following functions are used as blend operations. But unlike the
+ * `alpha_blend`, these functions take an ARGB16161616 pixel from the
+ * source, convert it to a specific format, and store it in the destination.
+ *
+ * They are used in the `compose_active_planes` and `write_wb_buffer` to
+ * copy and convert one pixel from/to the output buffer to/from
+ * another buffer (e.g. writeback buffer, primary plane buffer).
+ */
+
+void convert_to_ARGB8888(u64 argb_src1, u64 argb_src2, int x, int y,
+ struct vkms_composer *dst_composer)
+{
+ u8 *pixel_addr = packed_pixels_addr(dst_composer, x, y);
+
+ /*
+ * This sequence below is important because the format's byte order is
+ * in little-endian. In the case of the ARGB8888 the memory is
+ * organized this way:
+ *
+ * | Addr | = blue channel
+ * | Addr + 1 | = green channel
+ * | Addr + 2 | = Red channel
+ * | Addr + 3 | = Alpha channel
+ */
+ pixel_addr[0] = DIV_ROUND_UP(argb_src1 & 0xffffllu, 257);
+ pixel_addr[1] = DIV_ROUND_UP((argb_src1 & (0xffffllu << 16)) >> 16, 257);
+ pixel_addr[2] = DIV_ROUND_UP((argb_src1 & (0xffffllu << 32)) >> 32, 257);
+ pixel_addr[3] = DIV_ROUND_UP((argb_src1 & (0xffffllu << 48)) >> 48, 257);
This could be potentially expensive if the compiler ends up using an
actual div instruction.
Yes, I'm using the DIV_ROUND_UP because I couldn't figure out how the
"Faster div by 255" works to adapt to 16 bits.
Btw. this would be shorter to write as
(argb_src1 >> 16) & 0xffff
etc.
I will use it in the V2. Thanks.
Thanks,
pq
+}
+
+void convert_to_XRGB8888(u64 argb_src1, u64 argb_src2, int x, int y,
+ struct vkms_composer *dst_composer)
+{
+ u8 *pixel_addr = packed_pixels_addr(dst_composer, x, y);
+
+ pixel_addr[0] = DIV_ROUND_UP(argb_src1 & 0xffffllu, 257);
+ pixel_addr[1] = DIV_ROUND_UP((argb_src1 & (0xffffllu << 16)) >> 16, 257);
+ pixel_addr[2] = DIV_ROUND_UP((argb_src1 & (0xffffllu << 32)) >> 32, 257);
+ pixel_addr[3] = 0xff;
+}
+
+void convert_to_ARGB16161616(u64 argb_src1, u64 argb_src2, int x, int y,
+ struct vkms_composer *dst_composer)
+{
+ __le64 *pixel_addr = packed_pixels_addr(dst_composer, x, y);
+
+ *pixel_addr = cpu_to_le64(argb_src1);
+}
+
+#endif /* _VKMS_FORMATS_H_ */
