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Date: Mon, 6 Jan 2014 14:37:16 -0800 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Paulo Zanoni <paulo.r.zanoni@...el.com>, Dave Jones <davej@...hat.com>, Daniel Vetter <daniel.vetter@...ll.ch> Subject: [PATCH 3.12 075/144] drm/i915: change CRTC assertion on LCPLL disable 3.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paulo Zanoni <paulo.r.zanoni@...el.com> commit 96b4026878d9dac71bd4c3d6e05c7fbb16a3e0aa upstream. Currently, PC8 is enabled at modeset_global_resources, which is called after intel_modeset_update_state. Due to this, there's a small race condition on the case where we start enabling PC8, then do a modeset while PC8 is still being enabled. The racing condition triggers a WARN because intel_modeset_update_state will mark the CRTC as enabled, then the thread that's still enabling PC8 might look at the data structure and think that PC8 is being enabled while a pipe is enabled. Despite the WARN, this is not really a bug since we'll wait for the PC8-enabling thread to finish when we call modeset_global_resources. The spec says the CRTC cannot be enabled when we disable LCPLL, so we had a check for crtc->base.enabled. If we change to crtc->active we will still prevent disabling LCPLL while the CRTC is enabled, and we will also prevent the WARN above. This is a replacement for the previous patch named "drm/i915: get/put PC8 when we get/put a CRTC" Testcase: igt/pm_pc8/modeset-lpsp-stress-no-wait Signed-off-by: Paulo Zanoni <paulo.r.zanoni@...el.com> (cherry picked from commit 798183c54799fbe1e5a5bfabb3a8c0505ffd2149 from -next due to Dave's report.) Reported-by: Dave Jones <davej@...hat.com> Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- drivers/gpu/drm/i915/intel_display.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -6009,7 +6009,7 @@ static void assert_can_disable_lcpll(str uint32_t val; list_for_each_entry(crtc, &dev->mode_config.crtc_list, base.head) - WARN(crtc->base.enabled, "CRTC for pipe %c enabled\n", + WARN(crtc->active, "CRTC for pipe %c enabled\n", pipe_name(crtc->pipe)); WARN(I915_READ(HSW_PWR_WELL_DRIVER), "Power well on\n"); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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