[RFC] PCI: tegra: Revert raw_violation_fixup for tegra124

From: Nicolas Chauvet <kwizart@gmail.com>
To: Manikanta Maddireddy <mmaddireddy@nvidia.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	linux-tegra@vger.kernel.org, linux-pci@vger.kernel.org,
	Nicolas Chauvet <kwizart@gmail.com>
Subject: [RFC] PCI: tegra: Revert raw_violation_fixup for tegra124
Date: Mon, 20 Apr 2020 18:43:04 +0200	[thread overview]
Message-ID: <20200420164304.28810-1-kwizart@gmail.com> (raw)

As reported in https://bugzilla.kernel.org/206217 , raw_violation_fixup
is causing more harm than good in some common use-cases.

This patch as RFC is a partial revert of the 191cd6fb5 commit:
 "PCI: tegra: Add SW fixup for RAW violations" 
that was first introduced in 5.3 kernel.
This fix the following regression since then.


When using both the network NIC and I/O on MMC this can lead to the
following message on jetson-tk1:

 NETDEV WATCHDOG: enp1s0 (r8169): transmit queue 0 timed out

and

 pcieport 0000:00:02.0: AER: Uncorrected (Non-Fatal) error received: 0000:01:00.0
 r8169 0000:01:00.0: AER: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Requester ID)
 r8169 0000:01:00.0: AER:   device [10ec:8168] error status/mask=00004000/00400000
 r8169 0000:01:00.0: AER:    [14] CmpltTO                (First)
 r8169 0000:01:00.0: AER: can't recover (no error_detected callback)
 pcieport 0000:00:02.0: AER: device recovery failed


After that, the ethernet NIC isn't functional anymore even after reloading
the module.
After a reboot, this is reproducible by copying a large file over the
ethernet NIC to the MMC.
For some reasons this cannot be reproduced when the same file is copied
to a tmpfs.


This patch is RFC because it requires more understanding from Nvidia.
 - Is the fixup (available in l4t downstrem) still needed for upstream ?
 - Is there a need to update the fixup values for upstream ?
 - If the fixup is reverted, does the hw bug can still be seen with
   upstream ?

Others can also provides more understanding:
 - Conditions to reproduce the bug (or not)...


Signed-off-by: Nicolas Chauvet <kwizart@gmail.com>
---
 drivers/pci/controller/pci-tegra.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pci-tegra.c b/drivers/pci/controller/pci-tegra.c
index 3e64ba6a36a8..4027e074094a 100644
--- a/drivers/pci/controller/pci-tegra.c
+++ b/drivers/pci/controller/pci-tegra.c
@@ -2470,7 +2470,7 @@ static const struct tegra_pcie_soc tegra124_pcie = {
 	.program_uphy = true,
 	.update_clamp_threshold = true,
 	.program_deskew_time = false,
-	.raw_violation_fixup = true,
+	.raw_violation_fixup = false,
 	.update_fc_timer = false,
 	.has_cache_bars = false,
 	.ectl.enable = false,
-- 
2.25.2

