drm/i915: Add extra paranoia to ILK watermark calculations
Our low-level watermark calculation functions don't get called when the
CRTC is disabled or the relevant plane is invisible, so they should
never see a zero htotal or zero bpp. However add some checks to ensure
this is true so that we don't wind up dividing by zero if we make a
mistake elsewhere in the driver (which the atomic watermark series has
revealed we might be).
References: http://lists.freedesktop.org/archives/intel-gfx/2015-October/077370.html
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1449171462-30763-6-git-send-email-matthew.d.roper@intel.com
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 0f22d11..f9cbd2e 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -1672,6 +1672,9 @@
if (pipe_h < pfit_h)
pipe_h = pfit_h;
+ if (WARN_ON(!pfit_w || !pfit_h))
+ return pixel_rate;
+
pixel_rate = div_u64((uint64_t) pixel_rate * pipe_w * pipe_h,
pfit_w * pfit_h);
}
@@ -1703,6 +1706,8 @@
if (WARN(latency == 0, "Latency value missing\n"))
return UINT_MAX;
+ if (WARN_ON(!pipe_htotal))
+ return UINT_MAX;
ret = (latency * pixel_rate) / (pipe_htotal * 10000);
ret = (ret + 1) * horiz_pixels * bytes_per_pixel;
@@ -1713,6 +1718,17 @@
static uint32_t ilk_wm_fbc(uint32_t pri_val, uint32_t horiz_pixels,
uint8_t bytes_per_pixel)
{
+ /*
+ * Neither of these should be possible since this function shouldn't be
+ * called if the CRTC is off or the plane is invisible. But let's be
+ * extra paranoid to avoid a potential divide-by-zero if we screw up
+ * elsewhere in the driver.
+ */
+ if (WARN_ON(!bytes_per_pixel))
+ return 0;
+ if (WARN_ON(!horiz_pixels))
+ return 0;
+
return DIV_ROUND_UP(pri_val * 64, horiz_pixels * bytes_per_pixel) + 2;
}