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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>
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@ -1672,6 +1672,9 @@ uint32_t ilk_pipe_pixel_rate(const struct intel_crtc_state *pipe_config)
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if (pipe_h < pfit_h)
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pipe_h = pfit_h;
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if (WARN_ON(!pfit_w || !pfit_h))
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return pixel_rate;
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pixel_rate = div_u64((uint64_t) pixel_rate * pipe_w * pipe_h,
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pfit_w * pfit_h);
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}
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@ -1703,6 +1706,8 @@ static uint32_t ilk_wm_method2(uint32_t pixel_rate, uint32_t pipe_htotal,
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if (WARN(latency == 0, "Latency value missing\n"))
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return UINT_MAX;
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if (WARN_ON(!pipe_htotal))
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return UINT_MAX;
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ret = (latency * pixel_rate) / (pipe_htotal * 10000);
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ret = (ret + 1) * horiz_pixels * bytes_per_pixel;
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@ -1713,6 +1718,17 @@ static uint32_t ilk_wm_method2(uint32_t pixel_rate, uint32_t pipe_htotal,
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static uint32_t ilk_wm_fbc(uint32_t pri_val, uint32_t horiz_pixels,
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uint8_t bytes_per_pixel)
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{
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/*
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* Neither of these should be possible since this function shouldn't be
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* called if the CRTC is off or the plane is invisible. But let's be
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* extra paranoid to avoid a potential divide-by-zero if we screw up
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* elsewhere in the driver.
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*/
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if (WARN_ON(!bytes_per_pixel))
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return 0;
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if (WARN_ON(!horiz_pixels))
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return 0;
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return DIV_ROUND_UP(pri_val * 64, horiz_pixels * bytes_per_pixel) + 2;
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}
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