| Message ID | 20241116-presets-v1-2-878a837a4fee@quicinc.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | PCI: dwc: Add support for configuring lane equalization presets | expand |
On 16.11.2024 2:37 AM, Krishna chaitanya chundru wrote: > PCIe equalization presets are predefined settings used to optimize > signal integrity by compensating for signal loss and distortion in > high-speed data transmission. > > As per PCIe spec 6.0.1 revision section 8.3.3.3 & 4.2.4 for data rates > of 8.0 GT/s, 16.0 GT/s, 32.0 GT/s, and 64.0 GT/s, there is a way to > configure lane equalization presets for each lane to enhance the PCIe > link reliability. Each preset value represents a different combination > of pre-shoot and de-emphasis values. For each data rate, different > registers are defined: for 8.0 GT/s, registers are defined in section > 7.7.3.4; for 16.0 GT/s, in section 7.7.5.9, etc. The 8.0 GT/s rate has > an extra receiver preset hint, requiring 16 bits per lane, while the > remaining data rates use 8 bits per lane. > > Based on the number of lanes and the supported data rate, this function > reads the device tree property and stores in the presets structure. > > Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com> > --- > drivers/pci/of.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ > drivers/pci/pci.h | 17 +++++++++++++-- > 2 files changed, 77 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/of.c b/drivers/pci/of.c > index dacea3fc5128..0d37bc231956 100644 > --- a/drivers/pci/of.c > +++ b/drivers/pci/of.c > @@ -826,3 +826,65 @@ u32 of_pci_get_slot_power_limit(struct device_node *node, > return slot_power_limit_mw; > } > EXPORT_SYMBOL_GPL(of_pci_get_slot_power_limit); > + > +int of_pci_get_equalization_presets(struct device *dev, > + struct pci_eq_presets *presets, > + int num_lanes) > +{ > + int ret; > + > + if (of_property_present(dev->of_node, "eq-presets-8gts")) { > + presets->eq_presets_8gts = devm_kzalloc(dev, sizeof(u16) * num_lanes, GFP_KERNEL); > + if (!presets->eq_presets_8gts) If you make this an array with enum indices, you can make a for loop and read "eq-presets-%ugts", (8 << i) Konrad
Hi Krishna, kernel test robot noticed the following build warnings: [auto build test WARNING on 81983758430957d9a5cb3333fe324fd70cf63e7e] url: https://github.com/intel-lab-lkp/linux/commits/Krishna-chaitanya-chundru/arm64-dts-qcom-x1e80100-Add-PCIe-lane-equalization-preset-properties/20241117-000950 base: 81983758430957d9a5cb3333fe324fd70cf63e7e patch link: https://lore.kernel.org/r/20241116-presets-v1-2-878a837a4fee%40quicinc.com patch subject: [PATCH 2/4] PCI: of: Add API to retrieve equalization presets from device tree config: i386-buildonly-randconfig-005-20241117 (https://download.01.org/0day-ci/archive/20241117/202411171316.4RG7T90F-lkp@intel.com/config) compiler: gcc-12 (Debian 12.2.0-14) 12.2.0 reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241117/202411171316.4RG7T90F-lkp@intel.com/reproduce) If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot <lkp@intel.com> | Closes: https://lore.kernel.org/oe-kbuild-all/202411171316.4RG7T90F-lkp@intel.com/ All warnings (new ones prefixed by >>): In file included from drivers/pci/controller/dwc/pcie-designware.c:23: >> drivers/pci/controller/dwc/../../pci.h:803:12: warning: 'of_pci_get_equalization_presets' defined but not used [-Wunused-function] 803 | static int of_pci_get_equalization_presets(struct device *dev, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ vim +/of_pci_get_equalization_presets +803 drivers/pci/controller/dwc/../../pci.h 802 > 803 static int of_pci_get_equalization_presets(struct device *dev, 804 struct pci_eq_presets *presets, 805 int num_lanes) 806 { 807 return 0; 808 } 809 #endif /* CONFIG_OF */ 810
Hi Krishna, kernel test robot noticed the following build warnings: [auto build test WARNING on 81983758430957d9a5cb3333fe324fd70cf63e7e] url: https://github.com/intel-lab-lkp/linux/commits/Krishna-chaitanya-chundru/arm64-dts-qcom-x1e80100-Add-PCIe-lane-equalization-preset-properties/20241117-000950 base: 81983758430957d9a5cb3333fe324fd70cf63e7e patch link: https://lore.kernel.org/r/20241116-presets-v1-2-878a837a4fee%40quicinc.com patch subject: [PATCH 2/4] PCI: of: Add API to retrieve equalization presets from device tree config: parisc-defconfig (https://download.01.org/0day-ci/archive/20241117/202411171502.1POu4enK-lkp@intel.com/config) compiler: hppa-linux-gcc (GCC) 14.2.0 reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241117/202411171502.1POu4enK-lkp@intel.com/reproduce) If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot <lkp@intel.com> | Closes: https://lore.kernel.org/oe-kbuild-all/202411171502.1POu4enK-lkp@intel.com/ All warnings (new ones prefixed by >>): In file included from drivers/pci/access.c:8: >> drivers/pci/pci.h:803:12: warning: 'of_pci_get_equalization_presets' defined but not used [-Wunused-function] 803 | static int of_pci_get_equalization_presets(struct device *dev, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- In file included from drivers/pci/msi/pcidev_msi.c:5: >> drivers/pci/msi/../pci.h:803:12: warning: 'of_pci_get_equalization_presets' defined but not used [-Wunused-function] 803 | static int of_pci_get_equalization_presets(struct device *dev, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- In file included from drivers/pci/pcie/aspm.c:27: >> drivers/pci/pcie/../pci.h:803:12: warning: 'of_pci_get_equalization_presets' defined but not used [-Wunused-function] 803 | static int of_pci_get_equalization_presets(struct device *dev, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ vim +/of_pci_get_equalization_presets +803 drivers/pci/pci.h 802 > 803 static int of_pci_get_equalization_presets(struct device *dev, 804 struct pci_eq_presets *presets, 805 int num_lanes) 806 { 807 return 0; 808 } 809 #endif /* CONFIG_OF */ 810
diff --git a/drivers/pci/of.c b/drivers/pci/of.c index dacea3fc5128..0d37bc231956 100644 --- a/drivers/pci/of.c +++ b/drivers/pci/of.c @@ -826,3 +826,65 @@ u32 of_pci_get_slot_power_limit(struct device_node *node, return slot_power_limit_mw; } EXPORT_SYMBOL_GPL(of_pci_get_slot_power_limit); + +int of_pci_get_equalization_presets(struct device *dev, + struct pci_eq_presets *presets, + int num_lanes) +{ + int ret; + + if (of_property_present(dev->of_node, "eq-presets-8gts")) { + presets->eq_presets_8gts = devm_kzalloc(dev, sizeof(u16) * num_lanes, GFP_KERNEL); + if (!presets->eq_presets_8gts) + return -ENOMEM; + + ret = of_property_read_u16_array(dev->of_node, "eq-presets-8gts", + presets->eq_presets_8gts, num_lanes); + if (ret) { + dev_err(dev, "Error reading eq-presets-8gts %d\n", ret); + return ret; + } + } + + if (of_property_present(dev->of_node, "eq-presets-16gts")) { + presets->eq_presets_16gts = devm_kzalloc(dev, sizeof(u8) * num_lanes, GFP_KERNEL); + if (!presets->eq_presets_16gts) + return -ENOMEM; + + ret = of_property_read_u8_array(dev->of_node, "eq-presets-16gts", + presets->eq_presets_16gts, num_lanes); + if (ret) { + dev_err(dev, "Error reading eq-presets-16gts %d\n", ret); + return ret; + } + } + + if (of_property_present(dev->of_node, "eq-presets-32gts")) { + presets->eq_presets_32gts = devm_kzalloc(dev, sizeof(u8) * num_lanes, GFP_KERNEL); + if (!presets->eq_presets_32gts) + return -ENOMEM; + + ret = of_property_read_u8_array(dev->of_node, "eq-presets-32gts", + presets->eq_presets_32gts, num_lanes); + if (ret) { + dev_err(dev, "Error reading eq-presets-32gts %d\n", ret); + return ret; + } + } + + if (of_property_present(dev->of_node, "eq-presets-64gts")) { + presets->eq_presets_64gts = devm_kzalloc(dev, sizeof(u8) * num_lanes, GFP_KERNEL); + if (!presets->eq_presets_64gts) + return -ENOMEM; + + ret = of_property_read_u8_array(dev->of_node, "eq-presets-64gts", + presets->eq_presets_64gts, num_lanes); + if (ret) { + dev_err(dev, "Error reading eq-presets-64gts %d\n", ret); + return ret; + } + } + + return 0; +} +EXPORT_SYMBOL_GPL(of_pci_get_equalization_presets); diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 14d00ce45bfa..757872f0cc35 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -731,7 +731,12 @@ static inline u64 pci_rebar_size_to_bytes(int size) } struct device_node; - +struct pci_eq_presets { + u16 *eq_presets_8gts; + u8 *eq_presets_16gts; + u8 *eq_presets_32gts; + u8 *eq_presets_64gts; +}; #ifdef CONFIG_OF int of_pci_parse_bus_range(struct device_node *node, struct resource *res); int of_get_pci_domain_nr(struct device_node *node); @@ -746,7 +751,9 @@ void pci_set_bus_of_node(struct pci_bus *bus); void pci_release_bus_of_node(struct pci_bus *bus); int devm_of_pci_bridge_init(struct device *dev, struct pci_host_bridge *bridge); - +int of_pci_get_equalization_presets(struct device *dev, + struct pci_eq_presets *presets, + int num_lanes); #else static inline int of_pci_parse_bus_range(struct device_node *node, struct resource *res) @@ -793,6 +800,12 @@ static inline int devm_of_pci_bridge_init(struct device *dev, struct pci_host_br return 0; } +static int of_pci_get_equalization_presets(struct device *dev, + struct pci_eq_presets *presets, + int num_lanes) +{ + return 0; +} #endif /* CONFIG_OF */ struct of_changeset;
PCIe equalization presets are predefined settings used to optimize signal integrity by compensating for signal loss and distortion in high-speed data transmission. As per PCIe spec 6.0.1 revision section 8.3.3.3 & 4.2.4 for data rates of 8.0 GT/s, 16.0 GT/s, 32.0 GT/s, and 64.0 GT/s, there is a way to configure lane equalization presets for each lane to enhance the PCIe link reliability. Each preset value represents a different combination of pre-shoot and de-emphasis values. For each data rate, different registers are defined: for 8.0 GT/s, registers are defined in section 7.7.3.4; for 16.0 GT/s, in section 7.7.5.9, etc. The 8.0 GT/s rate has an extra receiver preset hint, requiring 16 bits per lane, while the remaining data rates use 8 bits per lane. Based on the number of lanes and the supported data rate, this function reads the device tree property and stores in the presets structure. Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com> --- drivers/pci/of.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ drivers/pci/pci.h | 17 +++++++++++++-- 2 files changed, 77 insertions(+), 2 deletions(-)