[PATCH 3.16 270/328] PCI: Reprogram bridge prefetch registers on resume

Ben Hutchings
2018-12-09T22:01:44Z

From: Daniel Drake <drake@endlessm.com>

commit 083874549fdfefa629dfa752785e20427dde1511 upstream.

On 38+ Intel-based ASUS products, the NVIDIA GPU becomes unusable after S3
suspend/resume. The affected products include multiple generations of
NVIDIA GPUs and Intel SoCs. After resume, nouveau logs many errors such
as:

fifo: fault 00 [READ] at 0000005555555000 engine 00 [GR] client 04
[HUB/FE] reason 4a [] on channel -1 [007fa91000 unknown]
DRM: failed to idle channel 0 [DRM]

Similarly, the NVIDIA proprietary driver also fails after resume (black
screen, 100% CPU usage in Xorg process). We shipped a sample to NVIDIA for
diagnosis, and their response indicated that it's a problem with the parent
PCI bridge (on the Intel SoC), not the GPU.

Runtime suspend/resume works fine, only S3 suspend is affected.

We found a workaround: on resume, rewrite the Intel PCI bridge
'Prefetchable Base Upper 32 Bits' register (PCI_PREF_BASE_UPPER32). In the
cases that I checked, this register has value 0 and we just have to rewrite
that value.

Linux already saves and restores PCI config space during suspend/resume,
but this register was being skipped because upon resume, it already has
value 0 (the correct, pre-suspend value).

Intel appear to have previously acknowledged this behaviour and the
requirement to rewrite this register:
https://bugzilla.kernel.org/show_bug.cgi?id=116851#c23

Based on that, rewrite the prefetch register values even when that appears
unnecessary.

We have confirmed this solution on all the affected models we have in-hands
(X542UQ, UX533FD, X530UN, V272UN).

Additionally, this solves an issue where r8169 MSI-X interrupts were broken
after S3 suspend/resume on ASUS X441UAR. This issue was recently worked
around in commit 7bb05b85bc2d ("r8169: don't use MSI-X on RTL8106e"). It
also fixes the same issue on RTL6186evl/8111evl on an Aimfor-tech laptop
that we had not yet patched. I suspect it will also fix the issue that was
worked around in commit 7c53a722459c ("r8169: don't use MSI-X on
RTL8168g").

Thomas Martitz reports that this change also solves an issue where the AMD
Radeon Polaris 10 GPU on the HP Zbook 14u G5 is unresponsive after S3
suspend/resume.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=201069
Signed-off-by: Daniel Drake <drake@endlessm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-By: Peter Wu <peter@lekensteyn.nl>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/pci/pci.c | 27 +++++++++++++++++++--------
1 file changed, 19 insertions(+), 8 deletions(-)

--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1014,12 +1014,12 @@ int pci_save_state(struct pci_dev *dev)
EXPORT_SYMBOL(pci_save_state);

static void pci_restore_config_dword(struct pci_dev *pdev, int offset,
- u32 saved_val, int retry)
+ u32 saved_val, int retry, bool force)
{
u32 val;

pci_read_config_dword(pdev, offset, &val);
- if (val == saved_val)
+ if (!force && val == saved_val)
return;

for (;;) {
@@ -1038,25 +1038,36 @@ static void pci_restore_config_dword(str
}

static void pci_restore_config_space_range(struct pci_dev *pdev,
- int start, int end, int retry)
+ int start, int end, int retry,
+ bool force)
{
int index;

for (index = end; index >= start; index--)
pci_restore_config_dword(pdev, 4 * index,
pdev->saved_config_space[index],
- retry);
+ retry, force);
}

static void pci_restore_config_space(struct pci_dev *pdev)
{
if (pdev->hdr_type == PCI_HEADER_TYPE_NORMAL) {
- pci_restore_config_space_range(pdev, 10, 15, 0);
+ pci_restore_config_space_range(pdev, 10, 15, 0, false);
/* Restore BARs before the command register. */
- pci_restore_config_space_range(pdev, 4, 9, 10);
- pci_restore_config_space_range(pdev, 0, 3, 0);
+ pci_restore_config_space_range(pdev, 4, 9, 10, false);
+ pci_restore_config_space_range(pdev, 0, 3, 0, false);
+ } else if (pdev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
+ pci_restore_config_space_range(pdev, 12, 15, 0, false);
+
+ /*
+ * Force rewriting of prefetch registers to avoid S3 resume
+ * issues on Intel PCI bridges that occur when these
+ * registers are not explicitly written.
+ */
+ pci_restore_config_space_range(pdev, 9, 11, 0, true);
+ pci_restore_config_space_range(pdev, 0, 8, 0, false);
} else {
- pci_restore_config_space_range(pdev, 0, 15, 0);
+ pci_restore_config_space_range(pdev, 0, 15, 0, false);
}
}