From cc33985d26c92a5c908c0185239c59ec35b8637c Mon Sep 17 00:00:00 2001 From: Lukas Wunner Date: Mon, 16 Feb 2026 08:46:13 +0100 Subject: [PATCH] PCI/ASPM: Fix pci_clear_and_set_config_dword() usage MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When aspm_calc_l12_info() programs the L1 PM Substates Control 1 register fields Common_Mode_Restore_Time, LTR_L1.2_THRESHOLD_Value and _Scale, it invokes pci_clear_and_set_config_dword() in an incorrect way: For the bits to clear it selects those corresponding to the field. So far so good. But for the bits to set it passes a full register value. pci_clear_and_set_config_dword() performs a boolean OR operation which sets all bits of that value, not just the ones that were just cleared. Thus, when setting the LTR_L1.2_THRESHOLD_Value and _Scale on the child of an ASPM link, aspm_calc_l12_info() also sets the Common_Mode_Restore_Time. That's a spec violation: PCIe r7.0 sec 7.8.3.3 says this field is RsvdP for Upstream Ports. On Adrià's Pixelbook Eve, Common_Mode_Restore_Time of the Intel 7265 "Stone Peak" wifi card is zero, yet aspm_calc_l12_info() does not preserve the zero bits but instead programs the value calculated for the Root Port into the wifi card. Likewise, when setting the Common_Mode_Restore_Time on the Root Port, aspm_calc_l12_info() also changes the LTR_L1.2_THRESHOLD_Value and _Scale from the initial 163840 nsec to 237568 nsec (due to ORing those fields), only to reduce it afterwards to 106496 nsec. Amend all invocations of pci_clear_and_set_config_dword() to only set bits which are cleared. Finally, when setting the T_POWER_ON_Value and _Scale on the Root Port and the wifi card, aspm_calc_l12_info() fails to preserve bits declared RsvdP and instead overwrites them with zeroes. Replace pci_write_config_dword() with pci_clear_and_set_config_dword() to avoid this. Fixes: aeda9adebab8 ("PCI/ASPM: Configure L1 substate settings") Link: https://bugzilla.kernel.org/show_bug.cgi?id=220705#c22 Signed-off-by: Lukas Wunner Signed-off-by: Bjorn Helgaas Tested-by: Adrià Vilanova Martínez Cc: stable@vger.kernel.org # v4.11+ Link: https://patch.msgid.link/5c1752d7512eed0f4ea57b84b12d7ee08ca61fc5.1771226659.git.lukas@wunner.de --- drivers/pci/pcie/aspm.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index 21f5d23e0b61..925373b98dff 100644 --- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -706,22 +706,29 @@ static void aspm_calc_l12_info(struct pcie_link_state *link, } /* Program T_POWER_ON times in both ports */ - pci_write_config_dword(parent, parent->l1ss + PCI_L1SS_CTL2, ctl2); - pci_write_config_dword(child, child->l1ss + PCI_L1SS_CTL2, ctl2); + pci_clear_and_set_config_dword(parent, parent->l1ss + PCI_L1SS_CTL2, + PCI_L1SS_CTL2_T_PWR_ON_VALUE | + PCI_L1SS_CTL2_T_PWR_ON_SCALE, ctl2); + pci_clear_and_set_config_dword(child, child->l1ss + PCI_L1SS_CTL2, + PCI_L1SS_CTL2_T_PWR_ON_VALUE | + PCI_L1SS_CTL2_T_PWR_ON_SCALE, ctl2); /* Program Common_Mode_Restore_Time in upstream device */ pci_clear_and_set_config_dword(parent, parent->l1ss + PCI_L1SS_CTL1, - PCI_L1SS_CTL1_CM_RESTORE_TIME, ctl1); + PCI_L1SS_CTL1_CM_RESTORE_TIME, + ctl1 & PCI_L1SS_CTL1_CM_RESTORE_TIME); /* Program LTR_L1.2_THRESHOLD time in both ports */ pci_clear_and_set_config_dword(parent, parent->l1ss + PCI_L1SS_CTL1, PCI_L1SS_CTL1_LTR_L12_TH_VALUE | PCI_L1SS_CTL1_LTR_L12_TH_SCALE, - ctl1); + ctl1 & (PCI_L1SS_CTL1_LTR_L12_TH_VALUE | + PCI_L1SS_CTL1_LTR_L12_TH_SCALE)); pci_clear_and_set_config_dword(child, child->l1ss + PCI_L1SS_CTL1, PCI_L1SS_CTL1_LTR_L12_TH_VALUE | PCI_L1SS_CTL1_LTR_L12_TH_SCALE, - ctl1); + ctl1 & (PCI_L1SS_CTL1_LTR_L12_TH_VALUE | + PCI_L1SS_CTL1_LTR_L12_TH_SCALE)); if (pl1_2_enables || cl1_2_enables) { pci_clear_and_set_config_dword(parent,