Re: [Intel-gfx] [PATCH] drm/i915: Avoid div-by-zero when pixel_multiplier is zero
On Mon, Jun 09, 2014 at 04:20:46PM +0300, ville.syrj...@linux.intel.com wrote: From: Ville Syrjälä ville.syrj...@linux.intel.com On certain platforms pixel_multiplier is read out in .get_pipe_config(), but it also gets used to calculate the pixel clock in intel_sdvo_get_config(). If the pipe is disable but some SDVO outputs are active, we may end up dividing by zero in intel_sdvo_get_config(). To avoid the problem simply check for zero pixel_multiplier and skip the division. Another attempt at fixing this involved populating pixel_multiplier to 1 even for disabled pipes, but that triggered a WARN because SDVO_CMD_GET_CLOCK_RATE_MULT command failed and thus encoder_pixel_multiplier was left at zero and didn't match pipe_config-pixel_multiplier. The divide by pixel_multiplier operation got introduced here: commit 18442d08786472c63a0a80c27f92b033dffc26de Author: Ville Syrjälä ville.syrj...@linux.intel.com Date: Fri Sep 13 16:00:08 2013 +0300 drm/i915: Fix port_clock and adjusted_mode.clock readout all over and it has caused a regression on certain machines since they would hit the div-by-zero during resume. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76520 Cc: sta...@vger.kernel.org # 3.13+ Tested-by: Tim Richardson t...@tim-richardson.net Signed-off-by: Ville Syrjälä ville.syrj...@linux.intel.com Reviewed-by: Daniel Vetter daniel.vet...@ffwll.ch --- drivers/gpu/drm/i915/intel_sdvo.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c index 6a4d5bc..20375cc 100644 --- a/drivers/gpu/drm/i915/intel_sdvo.c +++ b/drivers/gpu/drm/i915/intel_sdvo.c @@ -1385,7 +1385,9 @@ static void intel_sdvo_get_config(struct intel_encoder *encoder, SDVO_PORT_MULTIPLY_SHIFT) + 1; } - dotclock = pipe_config-port_clock / pipe_config-pixel_multiplier; + dotclock = pipe_config-port_clock; + if (pipe_config-pixel_multiplier) + dotclock /= pipe_config-pixel_multiplier; if (HAS_PCH_SPLIT(dev)) ironlake_check_encoder_dotclock(pipe_config, dotclock); -- 1.8.5.5 ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
Re: [Intel-gfx] [PATCH] drm/i915: Avoid div-by-zero when pixel_multiplier is zero
On Tue, 10 Jun 2014, Daniel Vetter dan...@ffwll.ch wrote: On Mon, Jun 09, 2014 at 04:20:46PM +0300, ville.syrj...@linux.intel.com wrote: From: Ville Syrjälä ville.syrj...@linux.intel.com On certain platforms pixel_multiplier is read out in .get_pipe_config(), but it also gets used to calculate the pixel clock in intel_sdvo_get_config(). If the pipe is disable but some SDVO outputs are active, we may end up dividing by zero in intel_sdvo_get_config(). To avoid the problem simply check for zero pixel_multiplier and skip the division. Another attempt at fixing this involved populating pixel_multiplier to 1 even for disabled pipes, but that triggered a WARN because SDVO_CMD_GET_CLOCK_RATE_MULT command failed and thus encoder_pixel_multiplier was left at zero and didn't match pipe_config-pixel_multiplier. The divide by pixel_multiplier operation got introduced here: commit 18442d08786472c63a0a80c27f92b033dffc26de Author: Ville Syrjälä ville.syrj...@linux.intel.com Date: Fri Sep 13 16:00:08 2013 +0300 drm/i915: Fix port_clock and adjusted_mode.clock readout all over and it has caused a regression on certain machines since they would hit the div-by-zero during resume. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76520 Cc: sta...@vger.kernel.org # 3.13+ Tested-by: Tim Richardson t...@tim-richardson.net Signed-off-by: Ville Syrjälä ville.syrj...@linux.intel.com Reviewed-by: Daniel Vetter daniel.vet...@ffwll.ch Pushed to -fixes, thanks for the patch and review. BR, Jani. --- drivers/gpu/drm/i915/intel_sdvo.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c index 6a4d5bc..20375cc 100644 --- a/drivers/gpu/drm/i915/intel_sdvo.c +++ b/drivers/gpu/drm/i915/intel_sdvo.c @@ -1385,7 +1385,9 @@ static void intel_sdvo_get_config(struct intel_encoder *encoder, SDVO_PORT_MULTIPLY_SHIFT) + 1; } -dotclock = pipe_config-port_clock / pipe_config-pixel_multiplier; +dotclock = pipe_config-port_clock; +if (pipe_config-pixel_multiplier) +dotclock /= pipe_config-pixel_multiplier; if (HAS_PCH_SPLIT(dev)) ironlake_check_encoder_dotclock(pipe_config, dotclock); -- 1.8.5.5 ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Jani Nikula, Intel Open Source Technology Center ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
[Intel-gfx] [PATCH] drm/i915: Avoid div-by-zero when pixel_multiplier is zero
From: Ville Syrjälä ville.syrj...@linux.intel.com On certain platforms pixel_multiplier is read out in .get_pipe_config(), but it also gets used to calculate the pixel clock in intel_sdvo_get_config(). If the pipe is disable but some SDVO outputs are active, we may end up dividing by zero in intel_sdvo_get_config(). To avoid the problem simply check for zero pixel_multiplier and skip the division. Another attempt at fixing this involved populating pixel_multiplier to 1 even for disabled pipes, but that triggered a WARN because SDVO_CMD_GET_CLOCK_RATE_MULT command failed and thus encoder_pixel_multiplier was left at zero and didn't match pipe_config-pixel_multiplier. The divide by pixel_multiplier operation got introduced here: commit 18442d08786472c63a0a80c27f92b033dffc26de Author: Ville Syrjälä ville.syrj...@linux.intel.com Date: Fri Sep 13 16:00:08 2013 +0300 drm/i915: Fix port_clock and adjusted_mode.clock readout all over and it has caused a regression on certain machines since they would hit the div-by-zero during resume. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76520 Cc: sta...@vger.kernel.org # 3.13+ Tested-by: Tim Richardson t...@tim-richardson.net Signed-off-by: Ville Syrjälä ville.syrj...@linux.intel.com --- drivers/gpu/drm/i915/intel_sdvo.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c index 6a4d5bc..20375cc 100644 --- a/drivers/gpu/drm/i915/intel_sdvo.c +++ b/drivers/gpu/drm/i915/intel_sdvo.c @@ -1385,7 +1385,9 @@ static void intel_sdvo_get_config(struct intel_encoder *encoder, SDVO_PORT_MULTIPLY_SHIFT) + 1; } - dotclock = pipe_config-port_clock / pipe_config-pixel_multiplier; + dotclock = pipe_config-port_clock; + if (pipe_config-pixel_multiplier) + dotclock /= pipe_config-pixel_multiplier; if (HAS_PCH_SPLIT(dev)) ironlake_check_encoder_dotclock(pipe_config, dotclock); -- 1.8.5.5 ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
