udl-kms: avoid division

Division is slow, so it shouldn't be done by the pixel generating code.
The driver supports only 2 or 4 bytes per pixel, so we can replace
division with a shift.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

3 files changed, 30 insertions, 26 deletions

diff --git a/drivers/gpu/drm/udl/udl_drv.h b/drivers/gpu/drm/udl/udl_drv.h
index 55c0cc309198..7588a9eb0ee0 100644
--- a/drivers/gpu/drm/udl/udl_drv.h
+++ b/drivers/gpu/drm/udl/udl_drv.h
@@ -112,7 +112,7 @@ udl_fb_user_fb_create(struct drm_device *dev,
                       struct drm_file *file,
                       const struct drm_mode_fb_cmd2 *mode_cmd);
 
-int udl_render_hline(struct drm_device *dev, int bpp, struct urb **urb_ptr,
+int udl_render_hline(struct drm_device *dev, int log_bpp, struct urb **urb_ptr,
                      const char *front, char **urb_buf_ptr,
                      u32 byte_offset, u32 device_byte_offset, u32 byte_width,
                      int *ident_ptr, int *sent_ptr);
diff --git a/drivers/gpu/drm/udl/udl_fb.c b/drivers/gpu/drm/udl/udl_fb.c
index c3f5867dac91..8746eeeec44d 100644
--- a/drivers/gpu/drm/udl/udl_fb.c
+++ b/drivers/gpu/drm/udl/udl_fb.c
@@ -90,7 +90,10 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, int y,
         int bytes_identical = 0;
         struct urb *urb;
         int aligned_x;
-        int bpp = fb->base.format->cpp[0];
+        int log_bpp;
+
+        BUG_ON(!is_power_of_2(fb->base.format->cpp[0]));
+        log_bpp = __ffs(fb->base.format->cpp[0]);
 
         if (!fb->active_16)
                 return 0;
@@ -125,12 +128,12 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, int y,
 
         for (i = y; i < y + height ; i++) {
                 const int line_offset = fb->base.pitches[0] * i;
-                const int byte_offset = line_offset + (x * bpp);
-                const int dev_byte_offset = (fb->base.width * bpp * i) + (x * bpp);
-                if (udl_render_hline(dev, bpp, &urb,
+                const int byte_offset = line_offset + (x << log_bpp);
+                const int dev_byte_offset = (fb->base.width * i + x) << log_bpp;
+                if (udl_render_hline(dev, log_bpp, &urb,
                                      (char *) fb->obj->vmapping,
                                      &cmd, byte_offset, dev_byte_offset,
-                                     width * bpp,
+                                     width << log_bpp,
                                      &bytes_identical, &bytes_sent))
                         goto error;
         }
@@ -149,7 +152,7 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, int y,
 error:
         atomic_add(bytes_sent, &udl->bytes_sent);
         atomic_add(bytes_identical, &udl->bytes_identical);
-        atomic_add(width*height*bpp, &udl->bytes_rendered);
+        atomic_add((width * height) << log_bpp, &udl->bytes_rendered);
         end_cycles = get_cycles();
         atomic_add(((unsigned int) ((end_cycles - start_cycles)
                     >> 10)), /* Kcycles */
diff --git a/drivers/gpu/drm/udl/udl_transfer.c b/drivers/gpu/drm/udl/udl_transfer.c
index b992644c17e6..f3331d33547a 100644
--- a/drivers/gpu/drm/udl/udl_transfer.c
+++ b/drivers/gpu/drm/udl/udl_transfer.c
@@ -83,12 +83,12 @@ static inline u16 pixel32_to_be16(const uint32_t pixel)
                 ((pixel >> 8) & 0xf800));
 }
 
-static inline u16 get_pixel_val16(const uint8_t *pixel, int bpp)
+static inline u16 get_pixel_val16(const uint8_t *pixel, int log_bpp)
 {
-        u16 pixel_val16 = 0;
-        if (bpp == 2)
+        u16 pixel_val16;
+        if (log_bpp == 1)
                 pixel_val16 = *(const uint16_t *)pixel;
-        else if (bpp == 4)
+        else
                 pixel_val16 = pixel32_to_be16(*(const uint32_t *)pixel);
         return pixel_val16;
 }
@@ -125,8 +125,9 @@ static void udl_compress_hline16(
         const u8 *const pixel_end,
         uint32_t *device_address_ptr,
         uint8_t **command_buffer_ptr,
-        const uint8_t *const cmd_buffer_end, int bpp)
+        const uint8_t *const cmd_buffer_end, int log_bpp)
 {
+        const int bpp = 1 << log_bpp;
         const u8 *pixel = *pixel_start_ptr;
         uint32_t dev_addr  = *device_address_ptr;
         uint8_t *cmd = *command_buffer_ptr;
@@ -153,12 +154,12 @@ static void udl_compress_hline16(
                 raw_pixels_count_byte = cmd++; /*  we'll know this later */
                 raw_pixel_start = pixel;
 
-                cmd_pixel_end = pixel + min3(MAX_CMD_PIXELS + 1UL,
-                                        (unsigned long)(pixel_end - pixel) / bpp,
-                                        (unsigned long)(cmd_buffer_end - 1 - cmd) / 2) * bpp;
+                cmd_pixel_end = pixel + (min3(MAX_CMD_PIXELS + 1UL,
+                                        (unsigned long)(pixel_end - pixel) >> log_bpp,
+                                        (unsigned long)(cmd_buffer_end - 1 - cmd) / 2) << log_bpp);
 
                 prefetch_range((void *) pixel, cmd_pixel_end - pixel);
-                pixel_val16 = get_pixel_val16(pixel, bpp);
+                pixel_val16 = get_pixel_val16(pixel, log_bpp);
 
                 while (pixel < cmd_pixel_end) {
                         const u8 *const start = pixel;
@@ -170,7 +171,7 @@ static void udl_compress_hline16(
                         pixel += bpp;
 
                         while (pixel < cmd_pixel_end) {
-                                pixel_val16 = get_pixel_val16(pixel, bpp);
+                                pixel_val16 = get_pixel_val16(pixel, log_bpp);
                                 if (pixel_val16 != repeating_pixel_val16)
                                         break;
                                 pixel += bpp;
@@ -179,10 +180,10 @@ static void udl_compress_hline16(
                         if (unlikely(pixel > start + bpp)) {
                                 /* go back and fill in raw pixel count */
                                 *raw_pixels_count_byte = (((start -
-                                                raw_pixel_start) / bpp) + 1) & 0xFF;
+                                                raw_pixel_start) >> log_bpp) + 1) & 0xFF;
 
                                 /* immediately after raw data is repeat byte */
-                                *cmd++ = (((pixel - start) / bpp) - 1) & 0xFF;
+                                *cmd++ = (((pixel - start) >> log_bpp) - 1) & 0xFF;
 
                                 /* Then start another raw pixel span */
                                 raw_pixel_start = pixel;
@@ -192,14 +193,14 @@ static void udl_compress_hline16(
 
                 if (pixel > raw_pixel_start) {
                         /* finalize last RAW span */
-                        *raw_pixels_count_byte = ((pixel-raw_pixel_start) / bpp) & 0xFF;
+                        *raw_pixels_count_byte = ((pixel - raw_pixel_start) >> log_bpp) & 0xFF;
                 } else {
                         /* undo unused byte */
                         cmd--;
                 }
 
-                *cmd_pixels_count_byte = ((pixel - cmd_pixel_start) / bpp) & 0xFF;
-                dev_addr += ((pixel - cmd_pixel_start) / bpp) * 2;
+                *cmd_pixels_count_byte = ((pixel - cmd_pixel_start) >> log_bpp) & 0xFF;
+                dev_addr += ((pixel - cmd_pixel_start) >> log_bpp) * 2;
         }
 
         if (cmd_buffer_end <= MIN_RLX_CMD_BYTES + cmd) {
@@ -222,19 +223,19 @@ static void udl_compress_hline16(
  * (that we can only write to, slowly, and can never read), and (optionally)
  * our shadow copy that tracks what's been sent to that hardware buffer.
  */
-int udl_render_hline(struct drm_device *dev, int bpp, struct urb **urb_ptr,
+int udl_render_hline(struct drm_device *dev, int log_bpp, struct urb **urb_ptr,
                      const char *front, char **urb_buf_ptr,
                      u32 byte_offset, u32 device_byte_offset,
                      u32 byte_width,
                      int *ident_ptr, int *sent_ptr)
 {
         const u8 *line_start, *line_end, *next_pixel;
-        u32 base16 = 0 + (device_byte_offset / bpp) * 2;
+        u32 base16 = 0 + (device_byte_offset >> log_bpp) * 2;
         struct urb *urb = *urb_ptr;
         u8 *cmd = *urb_buf_ptr;
         u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;
 
-        BUG_ON(!(bpp == 2 || bpp == 4));
+        BUG_ON(!(log_bpp == 1 || log_bpp == 2));
 
         line_start = (u8 *) (front + byte_offset);
         next_pixel = line_start;
@@ -244,7 +245,7 @@ int udl_render_hline(struct drm_device *dev, int bpp, struct urb **urb_ptr,
 
                 udl_compress_hline16(&next_pixel,
                              line_end, &base16,
-                             (u8 **) &cmd, (u8 *) cmd_end, bpp);
+                             (u8 **) &cmd, (u8 *) cmd_end, log_bpp);
 
                 if (cmd >= cmd_end) {
                         int len = cmd - (u8 *) urb->transfer_buffer;