[SRU][N][PATCH 2/3] UBUNTU: SAUCE: PCI/ASPM: Add notes about enabling PCI-PM L1SS to pci_enable_link_state(_locked)
En-Wei Wu
en-wei.wu at canonical.com
Mon Oct 21 09:28:31 UTC 2024
From: Jian-Hong Pan <jhp at endlessos.org>
BugLink: https://bugs.launchpad.net/bugs/2085092
According to "PCIe r6.0, sec 5.5.4", add note about D0 requirement in
pci_enable_link_state() kernel-doc.
Signed-off-by: Jian-Hong Pan <jhp at endlessos.org>
Acked-by: Bjorn Helgaas <bhelgaas at google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy at linux.intel.com>
(cherry picked from https://lore.kernel.org/linux-pci/20241001083438.10070-2-jhp@endlessos.org)
[En-Wei - need to fix this issue ASAP and the patch hasn't been merged yet]
Signed-off-by: En-Wei Wu <en-wei.wu at canonical.com>
---
drivers/pci/pcie/aspm.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 138ff0efa6dd..182226ce5c4e 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1450,6 +1450,9 @@ static int __pci_enable_link_state(struct pci_dev *pdev, int state, bool locked)
* touch the LNKCTL register. Also note that this does not enable states
* disabled by pci_disable_link_state(). Return 0 or a negative errno.
*
+ * Note: Ensure devices are in D0 before enabling PCI-PM L1 PM Substates, per
+ * PCIe r6.0, sec 5.5.4.
+ *
* @pdev: PCI device
* @state: Mask of ASPM link states to enable
*/
@@ -1466,6 +1469,9 @@ EXPORT_SYMBOL(pci_enable_link_state);
* can't touch the LNKCTL register. Also note that this does not enable states
* disabled by pci_disable_link_state(). Return 0 or a negative errno.
*
+ * Note: Ensure devices are in D0 before enabling PCI-PM L1 PM Substates, per
+ * PCIe r6.0, sec 5.5.4.
+ *
* @pdev: PCI device
* @state: Mask of ASPM link states to enable
*
--
2.43.0
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