This is a note to let you know that I've just added the patch titled
PCI: keystone: Fix race condition when initializing PHYs
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
pci-keystone-fix-race-condition-when-initializing-ph.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 7e76cfd1e54efc18eca65df943457e8d0332b491
Author: Siddharth Vadapalli <s-vadapalli@xxxxxx>
Date: Wed Sep 27 09:48:45 2023 +0530
PCI: keystone: Fix race condition when initializing PHYs
[ Upstream commit c12ca110c613a81cb0f0099019c839d078cd0f38 ]
The PCI driver invokes the PHY APIs using the ks_pcie_enable_phy()
function. The PHY in this case is the Serdes. It is possible that the
PCI instance is configured for two lane operation across two different
Serdes instances, using one lane of each Serdes.
In such a configuration, if the reference clock for one Serdes is
provided by the other Serdes, it results in a race condition. After the
Serdes providing the reference clock is initialized by the PCI driver by
invoking its PHY APIs, it is not guaranteed that this Serdes remains
powered on long enough for the PHY APIs based initialization of the
dependent Serdes. In such cases, the PLL of the dependent Serdes fails
to lock due to the absence of the reference clock from the former Serdes
which has been powered off by the PM Core.
Fix this by obtaining reference to the PHYs before invoking the PHY
initialization APIs and releasing reference after the initialization is
complete.
Link: https://lore.kernel.org/linux-pci/20230927041845.1222080-1-s-vadapalli@xxxxxx
Fixes: 49229238ab47 ("PCI: keystone: Cleanup PHY handling")
Signed-off-by: Siddharth Vadapalli <s-vadapalli@xxxxxx>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@xxxxxxxxxx>
Acked-by: Ravi Gunasekaran <r-gunasekaran@xxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/pci/controller/dwc/pci-keystone.c b/drivers/pci/controller/dwc/pci-keystone.c
index 920444b1cfc7..b18ddb2b9ef8 100644
--- a/drivers/pci/controller/dwc/pci-keystone.c
+++ b/drivers/pci/controller/dwc/pci-keystone.c
@@ -1305,7 +1305,16 @@ static int ks_pcie_probe(struct platform_device *pdev)
goto err_link;
}
+ /* Obtain references to the PHYs */
+ for (i = 0; i < num_lanes; i++)
+ phy_pm_runtime_get_sync(ks_pcie->phy[i]);
+
ret = ks_pcie_enable_phy(ks_pcie);
+
+ /* Release references to the PHYs */
+ for (i = 0; i < num_lanes; i++)
+ phy_pm_runtime_put_sync(ks_pcie->phy[i]);
+
if (ret) {
dev_err(dev, "failed to enable phy\n");
goto err_link;
