From: Mahesh Kumar <mahesh1.kumar@xxxxxxxxx>
This patch changes Watermak calculation to fixed point calculation.
Problem with current calculation is during plane_blocks_per_line
calculation we divide intermediate blocks with min_scanlines and
takes floor of the result because of integer operation.
hence we end-up assigning less blocks than required. Which leads to
flickers.
Signed-off-by: Mahesh Kumar <mahesh1.kumar@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_pm.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 0eaaadc..4263212 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3527,16 +3527,19 @@ static uint32_t skl_pipe_pixel_rate(const struct intel_crtc_state *config)
* for the read latency) and cpp should always be <= 8, so that
* should allow pixel_rate up to ~2 GHz which seems sufficient since max
* 2xcdclk is 1350 MHz and the pixel rate should never exceed that.
+ * Both Method1 & Method2 returns fixedpoint 16.16 output
*/
static uint32_t skl_wm_method1(uint32_t pixel_rate, uint8_t cpp, uint32_t latency)
{
- uint32_t wm_intermediate_val, ret;
+ uint64_t wm_intermediate_val;
+ uint32_t ret;
if (latency == 0)
return UINT_MAX;
- wm_intermediate_val = latency * pixel_rate * cpp / 512;
- ret = DIV_ROUND_UP(wm_intermediate_val, 1000);
+ wm_intermediate_val = latency * pixel_rate * cpp;
+ wm_intermediate_val <<= 16;
+ ret = DIV_ROUND_UP_ULL(wm_intermediate_val, 1000 * 512);
return ret;
}
@@ -3658,12 +3661,15 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
if (y_tiled) {
plane_blocks_per_line =
DIV_ROUND_UP(plane_bytes_per_line * y_min_scanlines, 512);
- plane_blocks_per_line /= y_min_scanlines;
+ plane_blocks_per_line = (plane_blocks_per_line << 16) /
+ y_min_scanlines;
} else if (x_tiled) {
plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512);
+ plane_blocks_per_line <<= 16;
} else {
plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512)
+ 1;
+ plane_blocks_per_line <<= 16;
}
method1 = skl_wm_method1(plane_pixel_rate, cpp, latency);
@@ -3690,7 +3696,7 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
selected_result = method1;
}
- res_blocks = selected_result + 1;
+ res_blocks = DIV_ROUND_UP(selected_result, 1 << 16) + 1;
res_lines = DIV_ROUND_UP(selected_result, plane_blocks_per_line);
if (level >= 1 && level <= 7) {
--
2.10.1
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