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From: Jian-Hong Pan <jhp@endlessos.org>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Johan Hovold <johan@kernel.org>,
	David Box <david.e.box@linux.intel.com>,
	=?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Damien Le Moal <dlemoal@kernel.org>,
	Nirmal Patel <nirmal.patel@linux.intel.com>,
	Jonathan Derrick <jonathan.derrick@linux.dev>,
	linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Jian-Hong Pan <jhp@endlessos.org>,
	Bjorn Helgaas <bhelgaas@google.com>
Subject: [PATCH v5 2/4] PCI/ASPM: Add notes about enabling PCI-PM L1SS to pci_enable_link_state(_locked)
Date: Wed, 24 Apr 2024 18:59:47 +0800
Message-ID: <20240424105946.21735-2-jhp@endlessos.org>
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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@endlessos.org>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
v3:
- Fix as readable comments

v4:
- The same

v5:
- Tweak and simplify the commit message

 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 2428d278e015..91a8b35b1ae2 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1446,6 +1446,9 @@ 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
  */
@@ -1462,6 +1465,9 @@ 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
  *
-- 
2.44.0