diff mbox series

[2/4] PCI: of: Add API to retrieve equalization presets from device tree

Message ID 20241116-presets-v1-2-878a837a4fee@quicinc.com
State New
Headers show
Series PCI: dwc: Add support for configuring lane equalization presets | expand

Commit Message

Krishna chaitanya chundru Nov. 16, 2024, 1:37 a.m. UTC 
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(-)

Comments

kernel test robot Nov. 17, 2024, 5:48 a.m. UTC | #1 
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
diff mbox series

Patch

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;