[PATCH v5 2/6] PCI: dwc: Don't poll L2 if QUIRK_NOL2POLL_IN_PM is existing in suspend
From: Richard Zhu <hongxing.zhu@nxp.com>
Date: 2025-09-02 08:02:46
Also in:
imx, linux-pci, lkml
Subsystem:
pci driver for synopsys designware, pci native host bridge and endpoint drivers, pci subsystem, the rest · Maintainers:
Jingoo Han, Manivannan Sadhasivam, Lorenzo Pieralisi, Krzysztof Wilczyński, Bjorn Helgaas, Linus Torvalds
Refer to PCIe r6.0, sec 5.2, fig 5-1 Link Power Management State Flow Diagram. Both L0 and L2/L3 Ready can be transferred to LDn directly. It's harmless to let dw_pcie_suspend_noirq() proceed suspend after the PME_Turn_Off is sent out, whatever the LTSSM state is in L2 or L3 after a recommended 10ms max wait refer to PCIe r6.0, sec 5.3.3.2.1 PME Synchronization. The LTSSM states are inaccessible on i.MX6QP and i.MX7D after the PME_Turn_Off is sent out. To support this case, don't poll L2 state and apply a simple delay of PCIE_PME_TO_L2_TIMEOUT_US(10ms) if the QUIRK_NOL2POLL_IN_PM flag is set in suspend. Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com> Reviewed-by: Frank Li <Frank.Li@nxp.com> --- .../pci/controller/dwc/pcie-designware-host.c | 34 +++++++++++++------ drivers/pci/controller/dwc/pcie-designware.h | 4 +++ 2 files changed, 28 insertions(+), 10 deletions(-)
diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 9d46d1f0334b..57a1ba08c427 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c@@ -1016,15 +1016,29 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci) return ret; } - ret = read_poll_timeout(dw_pcie_get_ltssm, val, - val == DW_PCIE_LTSSM_L2_IDLE || - val <= DW_PCIE_LTSSM_DETECT_WAIT, - PCIE_PME_TO_L2_TIMEOUT_US/10, - PCIE_PME_TO_L2_TIMEOUT_US, false, pci); - if (ret) { - /* Only log message when LTSSM isn't in DETECT or POLL */ - dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val); - return ret; + if (dwc_quirk(pci, QUIRK_NOL2POLL_IN_PM)) { + /* + * Add the QUIRK_NOL2_POLL_IN_PM case to avoid the read hang, + * when LTSSM is not powered in L2/L3/LDn properly. + * + * Refer to PCIe r6.0, sec 5.2, fig 5-1 Link Power Management + * State Flow Diagram. Both L0 and L2/L3 Ready can be + * transferred to LDn directly. On the LTSSM states poll broken + * platforms, add a max 10ms delay refer to PCIe r6.0, + * sec 5.3.3.2.1 PME Synchronization. + */ + mdelay(PCIE_PME_TO_L2_TIMEOUT_US/1000); + } else { + ret = read_poll_timeout(dw_pcie_get_ltssm, val, + val == DW_PCIE_LTSSM_L2_IDLE || + val <= DW_PCIE_LTSSM_DETECT_WAIT, + PCIE_PME_TO_L2_TIMEOUT_US/10, + PCIE_PME_TO_L2_TIMEOUT_US, false, pci); + if (ret) { + /* Only log message when LTSSM isn't in DETECT or POLL */ + dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val); + return ret; + } } /*
@@ -1040,7 +1054,7 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci) pci->suspended = true; - return ret; + return 0; } EXPORT_SYMBOL_GPL(dw_pcie_suspend_noirq);
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 00f52d472dcd..4e5bf6cb6ce8 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h@@ -295,6 +295,9 @@ /* Default eDMA LLP memory size */ #define DMA_LLP_MEM_SIZE PAGE_SIZE +#define QUIRK_NOL2POLL_IN_PM BIT(0) +#define dwc_quirk(pci, val) (pci->quirk_flag & val) + struct dw_pcie; struct dw_pcie_rp; struct dw_pcie_ep;
@@ -504,6 +507,7 @@ struct dw_pcie { const struct dw_pcie_ops *ops; u32 version; u32 type; + u32 quirk_flag; unsigned long caps; int num_lanes; int max_link_speed;
--
2.37.1