[PATCH v3 3/7] gpu/radeon: Set flag to indicate broken 64-bit MSI

[Benjamin Herrenschmidt]

Some radeon ASICs don't support all 64 address bits of MSIs despite
advertising support for 64-bit MSIs in their configuration space.

This breaks on systems such as IBM POWER7/8, where 64-bit MSIs can
be assigned with some of the high address bits set.

This makes use of the newly introduced "no_64bit_msi" flag in structure
pci_dev to allow the MSI allocation code to fallback to 32-bit MSIs
on those adapters.

Signed-off-by: Benjamin Herrenschmidt <***@kernel.crashing.org>
Reviewed-by: Alex Deucher <***@amd.com>
CC: <***@vger.kernel.org>
---

Adding Alex's review tag. Patch to the driver is identical to the
reviewed one, I dropped the arch/powerpc hunk rewrote the subject
and cset comment.
---
drivers/gpu/drm/radeon/radeon_irq_kms.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon_irq_kms.c b/drivers/gpu/drm/radeon/radeon_irq_kms.c
index 16807af..c74f12d 100644
--- a/drivers/gpu/drm/radeon/radeon_irq_kms.c
+++ b/drivers/gpu/drm/radeon/radeon_irq_kms.c
@@ -202,6 +202,16 @@ static bool radeon_msi_ok(struct radeon_device *rdev)
if (rdev->flags & RADEON_IS_AGP)
return false;

+ /*
+ * Older chips have a HW limitation, they can only generate 40 bits
+ * of address for "64-bit" MSIs which breaks on some platforms, notably
+ * IBM POWER servers, so we limit them
+ */
+ if (rdev->family < CHIP_BONAIRE) {
+ dev_info(rdev->dev, "radeon: MSI limited to 32-bit\n");
+ rdev->pdev->no_64bit_msi = 1;
+ }
+
/* force MSI on */
if (radeon_msi == 1)
return true;