On Thu, Aug 17, 2023 at 08:04:43AM +0530, Krishna chaitanya chundru wrote: > PCIe can operate on lower GEN speed if client decided based upon > the bandwidth & latency requirements. To support dynamic GEN speed > switch adding this sysfs support. Who does "client" refer to? I assume it's the system administrator, but of course the endpoint is involved in the hardware speed negotiation, so one could think of the endpoint as a "client" with its own speed capabilities and requirements. > To change the GEN speed the link should be in L0, so first disable > L0s & L1. > > L0s needs to be disabled at both RC & EP because L0s entry is > independent. For enabling L0s both ends of the link needs to support > it, so first check if L0s is supported on both ends and then enable > L0s. Is there a place to document this sysfs knob? Why should it be qcom-specific? This sounds like generic PCIe functionality. The ASPM stuff looks like it should be done by aspm.c, not done behind its back. Everything here looks generic (not qcom-specific) except the qcom_pcie_icc_update() and qcom_pcie_opp_update(). Maybe we need some core infrastructure around this. > This patch is dependent on "PCI: qcom: Add support for OPP" > https://lore.kernel.org/linux-arm-msm/1692192264-18515-1-git-send-email-quic_krichai@xxxxxxxxxxx/T/#t > > Signed-off-by: Krishna chaitanya chundru <quic_krichai@xxxxxxxxxxx> > --- > drivers/pci/controller/dwc/pcie-qcom.c | 141 +++++++++++++++++++++++++++++++++ > 1 file changed, 141 insertions(+) > > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c > index 831d158..ad67d17 100644 > --- a/drivers/pci/controller/dwc/pcie-qcom.c > +++ b/drivers/pci/controller/dwc/pcie-qcom.c > @@ -241,10 +241,150 @@ struct qcom_pcie { > const struct qcom_pcie_cfg *cfg; > struct dentry *debugfs; > bool suspended; > + bool l0s_supported; > }; > > #define to_qcom_pcie(x) dev_get_drvdata((x)->dev) > > +static void qcom_pcie_icc_update(struct qcom_pcie *pcie); > +static void qcom_pcie_opp_update(struct qcom_pcie *pcie); > + > +static int qcom_pcie_disable_l0s(struct pci_dev *pdev, void *userdata) > +{ > + int lnkctl; > + > + pci_read_config_dword(pdev, pci_pcie_cap(pdev) + PCI_EXP_LNKCTL, &lnkctl); > + lnkctl &= ~(PCI_EXP_LNKCTL_ASPM_L0S); > + pci_write_config_word(pdev, pci_pcie_cap(pdev) + PCI_EXP_LNKCTL, lnkctl); > + > + return 0; > +} > + > +static int qcom_pcie_check_l0s_support(struct pci_dev *pdev, void *userdata) > +{ > + struct pci_dev *parent = pdev->bus->self; > + struct qcom_pcie *pcie = userdata; > + struct dw_pcie *pci = pcie->pci; > + int lnkcap; > + > + /* check parent supports L0s */ > + if (parent) { > + dev_err(pci->dev, "parent\n"); > + pci_read_config_dword(parent, pci_pcie_cap(parent) + PCI_EXP_LNKCAP, > + &lnkcap); > + if (!(lnkcap & PCI_EXP_LNKCAP_ASPM_L0S)) { > + dev_info(pci->dev, "Parent does not support L0s\n"); > + pcie->l0s_supported = false; > + return 0; > + } > + } > + > + pci_read_config_dword(pdev, pci_pcie_cap(pdev) + PCI_EXP_LNKCAP, > + &lnkcap); > + dev_err(pci->dev, "child %x\n", lnkcap); > + if (!(lnkcap & PCI_EXP_LNKCAP_ASPM_L0S)) { > + dev_info(pci->dev, "Device does not support L0s\n"); > + pcie->l0s_supported = false; > + return 0; > + } > + > + return 0; > +} > + > +static int qcom_pcie_enable_l0s(struct pci_dev *pdev, void *userdata) > +{ > + int lnkctl; > + > + pci_read_config_dword(pdev, pci_pcie_cap(pdev) + PCI_EXP_LNKCTL, &lnkctl); > + lnkctl |= (PCI_EXP_LNKCTL_ASPM_L0S); > + pci_write_config_word(pdev, pci_pcie_cap(pdev) + PCI_EXP_LNKCTL, lnkctl); > + > + return 0; > +} > + > +static ssize_t qcom_pcie_speed_change_store(struct device *dev, > + struct device_attribute *attr, > + const char *buf, > + size_t count) > +{ > + unsigned int current_speed, target_speed, max_speed; > + struct qcom_pcie *pcie = dev_get_drvdata(dev); > + struct pci_bus *child, *root_bus = NULL; > + struct dw_pcie_rp *pp = &pcie->pci->pp; > + struct dw_pcie *pci = pcie->pci; > + struct pci_dev *pdev; > + u16 offset; > + u32 val; > + int ret; > + > + list_for_each_entry(child, &pp->bridge->bus->children, node) { > + if (child->parent == pp->bridge->bus) { > + root_bus = child; > + break; > + } > + } > + > + pdev = root_bus->self; > + > + offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP); > + > + val = readl(pci->dbi_base + offset + PCI_EXP_LNKCAP); > + max_speed = FIELD_GET(PCI_EXP_LNKCAP_SLS, val); > + > + val = readw(pci->dbi_base + offset + PCI_EXP_LNKSTA); > + current_speed = FIELD_GET(PCI_EXP_LNKSTA_CLS, val); > + > + ret = kstrtouint(buf, 10, &target_speed); > + if (ret) > + return ret; > + > + if (target_speed > max_speed) > + return -EINVAL; > + > + if (current_speed == target_speed) > + return count; > + > + pci_walk_bus(pp->bridge->bus, qcom_pcie_disable_l0s, pcie); > + > + /* Disable L1 */ > + val = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCTL); > + val &= ~(PCI_EXP_LNKCTL_ASPM_L1); > + dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCTL, val); > + > + /* Set target GEN speed */ > + val = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCTL2); > + val &= ~PCI_EXP_LNKCTL2_TLS; > + dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCTL2, val | target_speed); > + > + ret = pcie_retrain_link(pdev, true); > + if (ret) > + dev_err(dev, "Link retrain failed %d\n", ret); > + > + /* Enable L1 */ > + val = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCTL); > + val |= (PCI_EXP_LNKCTL_ASPM_L1); > + dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCTL, val); > + > + pcie->l0s_supported = true; > + pci_walk_bus(pp->bridge->bus, qcom_pcie_check_l0s_support, pcie); > + > + if (pcie->l0s_supported) > + pci_walk_bus(pp->bridge->bus, qcom_pcie_enable_l0s, pcie); > + > + qcom_pcie_icc_update(pcie); > + > + qcom_pcie_opp_update(pcie); > + > + return count; > +} > +static DEVICE_ATTR_WO(qcom_pcie_speed_change); > + > +static struct attribute *qcom_pcie_attrs[] = { > + &dev_attr_qcom_pcie_speed_change.attr, > + NULL, > +}; > +ATTRIBUTE_GROUPS(qcom_pcie); > + > static void qcom_ep_reset_assert(struct qcom_pcie *pcie) > { > gpiod_set_value_cansleep(pcie->reset, 1); > @@ -1716,6 +1856,7 @@ static struct platform_driver qcom_pcie_driver = { > .of_match_table = qcom_pcie_match, > .pm = &qcom_pcie_pm_ops, > .probe_type = PROBE_PREFER_ASYNCHRONOUS, > + .dev_groups = qcom_pcie_groups, > }, > }; > builtin_platform_driver(qcom_pcie_driver); > -- > 2.7.4 >
