drm/radeon/kms: add MSI module parameter

Allow the user to override whether MSIs are enabled
or not on supported ASICs.  MSIs are disabled by default
on IGP chips as they tend not to work.  However certain
IGP chips only seem to work with MSIs enabled.

I suspect this is a chipset or bios issue, but I'm not sure
what the proper fix is.  This will at least make diagnosing
and working around the problem much easier.

See:
https://bugs.freedesktop.org/show_bug.cgi?id=37679

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_irq_kms.c b/drivers/gpu/drm/radeon/radeon_irq_kms.c
index 914d9ee8fd3..8f86aeb2669 100644
--- a/drivers/gpu/drm/radeon/radeon_irq_kms.c
+++ b/drivers/gpu/drm/radeon/radeon_irq_kms.c
@@ -118,6 +118,12 @@ static bool radeon_msi_ok(struct radeon_device *rdev)
         if (rdev->flags & RADEON_IS_AGP)
                 return false;
 
+        /* force MSI on */
+        if (radeon_msi == 1)
+                return true;
+        else if (radeon_msi == 0)
+                return false;
+
         /* Quirks */
         /* HP RS690 only seems to work with MSIs. */
         if ((rdev->pdev->device == 0x791f) &&