lkml.org 
[lkml]   [2018]   [Apr]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[PATCH v1 1/2] PCI/ASPM: Disable ASPM L1.2 Substate if we don't have LTR
From
Date
From: Bjorn Helgaas <bhelgaas@google.com>

When in the ASPM L1.0 state (but not the PCI-PM L1.0 state), the most
recent LTR value and the LTR_L1.2_THRESHOLD determines whether the link
enters the L1.2 substate.

If we don't have LTR enabled, prevent the use of ASPM L1.2.

PCI-PM L1.2 may still be used because it doesn't depend on
LTR_L1.2_THRESHOLD (see PCIe r4.0, sec 5.5.1).

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
drivers/pci/pcie/aspm.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index f76eb7704f64..c687c817b47d 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -400,6 +400,15 @@ static void pcie_get_aspm_reg(struct pci_dev *pdev,
info->l1ss_cap = 0;
return;
}
+
+ /*
+ * If we don't have LTR for the entire path from the Root Complex
+ * to this device, we can't use ASPM L1.2 because it relies on the
+ * LTR_L1.2_THRESHOLD. See PCIe r4.0, secs 5.5.4, 6.18.
+ */
+ if (!pdev->ltr_path)
+ info->l1ss_cap &= ~PCI_L1SS_CAP_ASPM_L1_2;
+
pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CTL1,
&info->l1ss_ctl1);
pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CTL2,
\
 
 \ /
  Last update: 2018-04-19 23:06    [W:0.062 / U:0.344 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site