From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
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.syrjala@xxxxxxxxxxxxxxx>
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: <stable@xxxxxxxxxxxxxxx> # 3.13+
Tested-by: Tim Richardson <tim@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
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
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