On 22/09/2016 22:00, Paulo Zanoni wrote:
The confusing thing is that plane_blocks_per_line is listed as part of
the method 2 calculation but is also used for other things. We
calculated it in two different places and different ways: one inside
skl_wm_method2() and the other inside skl_compute_plane_wm(). The
skl_wm_method2() implementation is the one that matches the
specification.
With this patch we fix the skl_compute_plane_wm() calculation and just
pass it as a parameter to skl_wm_method2(). We also take care to not
modify the value of plane_bytes_per_line since we're going to rely on
it having a correct value in later patches.
This should affect the watermarks for Linear and Y-tiled.
From my analysis, it looks like the two plane_blocks_per_line
variables got out of sync on 0fda65680e92, but we can't really say
that commit was a regression, it looks like just an incomplete fix.
There's always the possibility that 0fda65680e92 matched our
specification at that time, and then later the specification changed.
Yes, it wouldn't be a regression since before that commit changing
tiling with page flips did not work at all.
Whether or not calculation was fully correct at the time I am not sure.
The formulas changed at least twice after the initial implementation so
both are possible.
Regards,
Tvrtko
v2: Try to add a "Fixes" tag (Maarten).
Fixes: 0fda65680e92 ("drm/i915/skl: Update watermarks for Y tiling")
Cc: stable@xxxxxxxxxxxxxxx
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Reviewed-by: Lyude <cpaul@xxxxxxxxxx>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_pm.c | 39 +++++++++++++++------------------------
1 file changed, 15 insertions(+), 24 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index a7f5f7f..a6ae7b7 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3494,30 +3494,14 @@ static uint32_t skl_wm_method1(uint32_t pixel_rate, uint8_t cpp, uint32_t latenc
}
static uint32_t skl_wm_method2(uint32_t pixel_rate, uint32_t pipe_htotal,
- uint32_t horiz_pixels, uint8_t cpp,
- uint64_t tiling, uint32_t latency,
- uint32_t y_min_scanlines)
+ uint32_t latency, uint32_t plane_blocks_per_line)
{
uint32_t ret;
- uint32_t plane_bytes_per_line, plane_blocks_per_line;
uint32_t wm_intermediate_val;
if (latency == 0)
return UINT_MAX;
- plane_bytes_per_line = horiz_pixels * cpp;
-
- if (tiling == I915_FORMAT_MOD_Y_TILED ||
- tiling == I915_FORMAT_MOD_Yf_TILED) {
- plane_bytes_per_line *= y_min_scanlines;
- plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512);
- plane_blocks_per_line /= y_min_scanlines;
- } else if (tiling == DRM_FORMAT_MOD_NONE) {
- plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512) + 1;
- } else {
- plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512);
- }
-
wm_intermediate_val = latency * pixel_rate;
ret = DIV_ROUND_UP(wm_intermediate_val, pipe_htotal * 1000) *
plane_blocks_per_line;
@@ -3606,17 +3590,24 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
y_min_scanlines = 4;
}
+ plane_bytes_per_line = width * cpp;
+ if (fb->modifier[0] == I915_FORMAT_MOD_Y_TILED ||
+ fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED) {
+ plane_blocks_per_line =
+ DIV_ROUND_UP(plane_bytes_per_line * y_min_scanlines, 512);
+ plane_blocks_per_line /= y_min_scanlines;
+ } else if (fb->modifier[0] == DRM_FORMAT_MOD_NONE) {
+ plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512)
+ + 1;
+ } else {
+ plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512);
+ }
+
method1 = skl_wm_method1(plane_pixel_rate, cpp, latency);
method2 = skl_wm_method2(plane_pixel_rate,
cstate->base.adjusted_mode.crtc_htotal,
- width,
- cpp,
- fb->modifier[0],
latency,
- y_min_scanlines);
-
- plane_bytes_per_line = width * cpp;
- plane_blocks_per_line = DIV_ROUND_UP(plane_bytes_per_line, 512);
+ plane_blocks_per_line);
if (fb->modifier[0] == I915_FORMAT_MOD_Y_TILED ||
fb->modifier[0] == I915_FORMAT_MOD_Yf_TILED) {
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