FAILED: patch "[PATCH] drm/i915: Disable MSI for all pre-gen5" failed to apply to 4.13-stable tree

From e38c2da01f76cca82b59ca612529b81df82a7cc7 Mon Sep 17 00:00:00 2001

The patch below does not apply to the 4.13-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e38c2da01f76cca82b59ca612529b81df82a7cc7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <[email protected]>
Date: Mon, 26 Jun 2017 23:30:51 +0300
Subject: [PATCH] drm/i915: Disable MSI for all pre-gen5
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

We have pretty clear evidence that MSIs are getting lost on g4x and somehow the interrupt logic doesn't seem to recover from that state even if we try hard to clear the IIR.

Disabling IER around the normal IIR clearing in the irq handler isn't sufficient to avoid this, so the problem really seems to be further up the interrupt chain. This should guarantee that there's always an edge if any IIR bits are set after the interrupt handler is done, which should normally guarantee that the CPU interrupt is generated. That approach seems to work perfectly on VLV/CHV, but apparently not on g4x.

MSI is documented to be broken on 965gm at least. The chipset spec says MSI is defeatured because interrupts can be delayed or lost, which fits well with what we're seeing on g4x. Previously we've already disabled GMBUS interrupts on g4x because somehow GMBUS manages to raise legacy interrupts even when MSI is enabled.

Since there's such widespread MSI breakahge all over in the pre-gen5 land let's just give up on MSI on these platforms.

Seqno reporting might be negatively affected by this since the legcy interrupts aren't guaranteed to be ordered with the seqno writes, whereas MSI interrupts may be? But an occasioanlly missed seqno seems like a small price to pay for generally working interrupts.

Cc [email protected]

Cc Diego Viola <[email protected]>

Tested-by Diego Viola <[email protected]>

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101261

Signed-off-by Ville Syrjälä <[email protected]>

Link http://patchwork.freedesktop.org/patch/msgid/[email protected]

Reviewed-by Daniel Vetter <[email protected]>

drivers/gpu/drm/i915/i915_drv.c +0 -2

index 43e925933688..a6bef9ee8703 100644
@@ -1141,10 +1141,12 @@ static int i915_driver_init_hw(struct drm_i915_private *dev_priv)
         * and the registers being closely associated.
         *
         * According to chipset errata, on the 965GM, MSI interrupts may
-        * be lost or delayed, but we use them anyways to avoid
-        * stuck interrupts on some machines.

Quoted 65 lines · On Wed, Sep 20, 2017 at 6:17 AM, <[email protected]> wrote:

The patch below does not apply to the 4.13-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e38c2da01f76cca82b59ca612529b81df82a7cc7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <[email protected]>
Date: Mon, 26 Jun 2017 23:30:51 +0300
Subject: [PATCH] drm/i915: Disable MSI for all pre-gen5
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

We have pretty clear evidence that MSIs are getting lost on g4x and somehow the interrupt logic doesn't seem to recover from that state even if we try hard to clear the IIR.

Disabling IER around the normal IIR clearing in the irq handler isn't sufficient to avoid this, so the problem really seems to be further up the interrupt chain. This should guarantee that there's always an edge if any IIR bits are set after the interrupt handler is done, which should normally guarantee that the CPU interrupt is generated. That approach seems to work perfectly on VLV/CHV, but apparently not on g4x.

MSI is documented to be broken on 965gm at least. The chipset spec says MSI is defeatured because interrupts can be delayed or lost, which fits well with what we're seeing on g4x. Previously we've already disabled GMBUS interrupts on g4x because somehow GMBUS manages to raise legacy interrupts even when MSI is enabled.

Since there's such widespread MSI breakahge all over in the pre-gen5 land let's just give up on MSI on these platforms.

Seqno reporting might be negatively affected by this since the legcy interrupts aren't guaranteed to be ordered with the seqno writes, whereas MSI interrupts may be? But an occasioanlly missed seqno seems like a small price to pay for generally working interrupts.

Cc [email protected]

Cc Diego Viola <[email protected]>

Tested-by Diego Viola <[email protected]>

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101261

Signed-off-by Ville Syrjälä <[email protected]>

Link http://patchwork.freedesktop.org/patch/msgid/[email protected]

Reviewed-by Daniel Vetter <[email protected]>

drivers/gpu/drm/i915/i915_drv.c +0 -2

index 43e925933688..a6bef9ee8703 100644
@@ -1141,10 +1141,12 @@ static int i915_driver_init_hw(struct drm_i915_private *dev_priv)
         * and the registers being closely associated.
         *
         * According to chipset errata, on the 965GM, MSI interrupts may
-        * be lost or delayed, but we use them anyways to avoid
-        * stuck interrupts on some machines.

drivers/gpu/drm/i915/i915_drv.c static int i915_driver_init_hw(struct drm_i915_private *dev_priv) · line 1152

Quoted 10 lines

drivers/gpu/drm/i915/i915_drv.c +5 -1

+        * be lost or delayed, and was defeatured. MSI interrupts seem to
+        * get lost on g4x as well, and interrupt delivery seems to stay
+        * properly dead afterwards. So we'll just disable them for all
+        * pre-gen5 chipsets.
         */
-       if (!IS_I945G(dev_priv) && !IS_I945GM(dev_priv)) {
+       if (INTEL_GEN(dev_priv) >= 5) {
                if (pci_enable_msi(pdev) < 0)
                        DRM_DEBUG_DRIVER("can't enable MSI");
        }

Hi Greg,

This patch was already merged in torvalds/linux.git before 4.13 was released, so it is already available in 4.13.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/gpu/drm/i915/i915_drv.c?id=e38c2da01f76cca82b59ca612529b81df82a7cc7

Thanks,
Diego