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Subject[PATCH 4.8 026/125] drm/i915/gen9: fix plane_blocks_per_line on watermarks calculations
Date
4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paulo Zanoni <paulo.r.zanoni@intel.com>

commit cf6c525a31fac11b0775b8c06c00a508c6356d9b upstream.

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.

v2: Try to add a "Fixes" tag (Maarten).

Fixes: 0fda65680e92 ("drm/i915/skl: Update watermarks for Y tiling")
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Lyude <cpaul@redhat.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1474578035-424-7-git-send-email-paulo.r.zanoni@intel.com
(cherry picked from commit 7a1a8aed67e0a60772defe3f6499eb340da48634)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/gpu/drm/i915/intel_pm.c | 39 +++++++++++++++------------------------
1 file changed, 15 insertions(+), 24 deletions(-)

--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3475,30 +3475,14 @@ static uint32_t skl_wm_method1(uint32_t
}

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;
@@ -3587,17 +3571,24 @@ static int skl_compute_plane_wm(const st
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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