Re: build failure of next-20220906 due to 396369d67549 ("drm: vkms: Add support to the RGB565 format")

[Melissa Wen]

On 09/06, Sudip Mukherjee wrote:
> On Tue, Sep 6, 2022 at 4:59 PM Sudip Mukherjee (Codethink)
> <sudipm.mukherjee@xxxxxxxxx> wrote:
> >
> > Hi All,
> >
> > The builds of next-20220906 fails for mips, xtensa and arm allmodconfig.
> >
> > The errors in mips and xtensa are:
> >
> > ERROR: modpost: "__divdi3" [drivers/gpu/drm/vkms/vkms.ko] undefined!
> > ERROR: modpost: "__udivdi3" [drivers/gpu/drm/vkms/vkms.ko] undefined!
> >
> > The error in arm is:
> >
> > ERROR: modpost: "__aeabi_uldivmod" [drivers/gpu/drm/vkms/vkms.ko] undefined!
> > ERROR: modpost: "__aeabi_ldivmod" [drivers/gpu/drm/vkms/vkms.ko] undefined!
> >
> >
> > Trying to do a git bisect to find out the offending commit.
> 
> git bisect points to 396369d67549 ("drm: vkms: Add support to the
> RGB565 format")

Hi Sudip,

Thanks for pointing out this issue.

I think we can replace the macros that are triggering those compilation
error by functions in drm/drm_fixed.h that do the same calculation.

I checked those errors when building for arm and i386 and the issues are
fixed after applying the patch below. I appreciate if you can test.

I didn't check with mips and xtensa, but I guess it works in the same
way.

Igor,

it would be good if you double-check the calculation and compare to your
previous results.

Thanks,

Melissa

---

From 0853d85c0b9d6108f916665ff55efa079f28bc53 Mon Sep 17 00:00:00 2001
From: Melissa Wen <mwen@xxxxxxxxxx>
Date: Wed, 7 Sep 2022 15:14:31 -0100
Subject: [PATCH] drm/vkms: fix 32 bits compilation error by replacing macros

Replace vkms_formats macro for fixed-point operations with functions
from drm/drm_fixed.h to do the same job and fix 32-bits compilation
errors.

Fixes: a19c2ac9858 ("drm: vkms: Add support to the RGB565 format")
Reported-by: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Melissa Wen <mwen@xxxxxxxxxx>
---
 drivers/gpu/drm/vkms/vkms_formats.c | 54 +++++++++++------------------
 1 file changed, 20 insertions(+), 34 deletions(-)

diff --git a/drivers/gpu/drm/vkms/vkms_formats.c b/drivers/gpu/drm/vkms/vkms_formats.c
index 30bf8e6660ad..5c2612b822d4 100644
--- a/drivers/gpu/drm/vkms/vkms_formats.c
+++ b/drivers/gpu/drm/vkms/vkms_formats.c
@@ -1,27 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0+
 
-#include <drm/drm_rect.h>
+#include <linux/kernel.h>
 #include <linux/minmax.h>
+#include <drm/drm_rect.h>
+#include <drm/drm_fixed.h>
 
 #include "vkms_formats.h"
 
-/* The following macros help doing fixed point arithmetic. */
-/*
- * With Fixed-Point scale 15 we have 17 and 15 bits of integer and fractional
- * parts respectively.
- *  | 0000 0000 0000 0000 0.000 0000 0000 0000 |
- * 31                                          0
- */
-#define SHIFT 15
-
-#define INT_TO_FIXED(a) ((a) << SHIFT)
-#define FIXED_MUL(a, b) ((s32)(((s64)(a) * (b)) >> SHIFT))
-#define FIXED_DIV(a, b) ((s32)(((s64)(a) << SHIFT) / (b)))
-/* This macro converts a fixed point number to int, and round half up it */
-#define FIXED_TO_INT_ROUND(a) (((a) + (1 << (SHIFT - 1))) >> SHIFT)
-#define INT_TO_FIXED_DIV(a, b) (FIXED_DIV(INT_TO_FIXED(a), INT_TO_FIXED(b)))
-#define INT_TO_FIXED_DIV(a, b) (FIXED_DIV(INT_TO_FIXED(a), INT_TO_FIXED(b)))
-
 static size_t pixel_offset(const struct vkms_frame_info *frame_info, int x, int y)
 {
 	return frame_info->offset + (y * frame_info->pitch)
@@ -137,20 +122,21 @@ static void RGB565_to_argb_u16(struct line_buffer *stage_buffer,
 	int x_limit = min_t(size_t, drm_rect_width(&frame_info->dst),
 			       stage_buffer->n_pixels);
 
-	s32 fp_rb_ratio = INT_TO_FIXED_DIV(65535, 31);
-	s32 fp_g_ratio = INT_TO_FIXED_DIV(65535, 63);
+	s32 fp_rb_ratio = drm_fixp_div(drm_int2fixp(65535), 31);
+	s32 fp_g_ratio = drm_fixp_div(drm_int2fixp(65535), 63);
 
 	for (size_t x = 0; x < x_limit; x++, src_pixels++) {
 		u16 rgb_565 = le16_to_cpu(*src_pixels);
-		s32 fp_r = INT_TO_FIXED((rgb_565 >> 11) & 0x1f);
-		s32 fp_g = INT_TO_FIXED((rgb_565 >> 5) & 0x3f);
-		s32 fp_b = INT_TO_FIXED(rgb_565 & 0x1f);
+		s32 fp_r = drm_int2fixp((rgb_565 >> 11) & 0x1f);
+		s32 fp_g = drm_int2fixp((rgb_565 >> 5) & 0x3f);
+		s32 fp_b = drm_int2fixp(rgb_565 & 0x1f);
 
 		out_pixels[x].a = (u16)0xffff;
-		out_pixels[x].r = FIXED_TO_INT_ROUND(FIXED_MUL(fp_r, fp_rb_ratio));
-		out_pixels[x].g = FIXED_TO_INT_ROUND(FIXED_MUL(fp_g, fp_g_ratio));
-		out_pixels[x].b = FIXED_TO_INT_ROUND(FIXED_MUL(fp_b, fp_rb_ratio));
+		out_pixels[x].r = drm_fixp2int(drm_fixp_mul(fp_r, fp_rb_ratio));
+		out_pixels[x].g = drm_fixp2int(drm_fixp_mul(fp_g, fp_g_ratio));
+		out_pixels[x].b = drm_fixp2int(drm_fixp_mul(fp_b, fp_rb_ratio));
 	}
+
 }
 
 
@@ -249,17 +235,17 @@ static void argb_u16_to_RGB565(struct vkms_frame_info *frame_info,
 	int x_limit = min_t(size_t, drm_rect_width(&frame_info->dst),
 			    src_buffer->n_pixels);
 
-	s32 fp_rb_ratio = INT_TO_FIXED_DIV(65535, 31);
-	s32 fp_g_ratio = INT_TO_FIXED_DIV(65535, 63);
+	s32 fp_rb_ratio = drm_fixp_div(drm_int2fixp(65535), 31);
+	s32 fp_g_ratio = drm_fixp_div(drm_int2fixp(65535), 63);
 
 	for (size_t x = 0; x < x_limit; x++, dst_pixels++) {
-		s32 fp_r = INT_TO_FIXED(in_pixels[x].r);
-		s32 fp_g = INT_TO_FIXED(in_pixels[x].g);
-		s32 fp_b = INT_TO_FIXED(in_pixels[x].b);
+		s32 fp_r = drm_int2fixp(in_pixels[x].r);
+		s32 fp_g = drm_int2fixp(in_pixels[x].g);
+		s32 fp_b = drm_int2fixp(in_pixels[x].b);
 
-		u16 r = FIXED_TO_INT_ROUND(FIXED_DIV(fp_r, fp_rb_ratio));
-		u16 g = FIXED_TO_INT_ROUND(FIXED_DIV(fp_g, fp_g_ratio));
-		u16 b = FIXED_TO_INT_ROUND(FIXED_DIV(fp_b, fp_rb_ratio));
+		u16 r = drm_fixp2int(drm_fixp_div(fp_r, fp_rb_ratio));
+		u16 g = drm_fixp2int(drm_fixp_div(fp_g, fp_g_ratio));
+		u16 b = drm_fixp2int(drm_fixp_div(fp_b, fp_rb_ratio));
 
 		*dst_pixels = cpu_to_le16(r << 11 | g << 5 | b);
 	}
-- 
2.35.1

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