From 87536bfea3d962fd0f2dcba1e5fc029d5c2b27d7 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Mon, 9 Jun 2014 16:20:46 +0300 Subject: [PATCH] drm/i915: Avoid div-by-zero when pixel_multiplier is zero MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit 2b85886a5457f5c5dbcd32edbd4e6bba0f4e8678 upstream. 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 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 Tested-by: Tim Richardson Reviewed-by: Daniel Vetter Signed-off-by: Ville Syrjälä Signed-off-by: Jani Nikula Signed-off-by: Greg Kroah-Hartman --- 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 cbc2fee..1890264 100644 --- a/drivers/gpu/drm/i915/intel_sdvo.c +++ b/drivers/gpu/drm/i915/intel_sdvo.c @@ -1383,7 +1383,9 @@ 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); -- 2.7.4