| Message ID | 20241223-preset_v2-v3-2-a339f475caf5@oss.qualcomm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | PCI: dwc: Add support for configuring lane equalization presets | expand |
On Mon, Dec 23, 2024 at 12:21:15PM +0530, 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 <krishna.chundru@oss.qualcomm.com> > --- > drivers/pci/of.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ > drivers/pci/pci.h | 17 +++++++++++++++-- > 2 files changed, 60 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/of.c b/drivers/pci/of.c > index dacea3fc5128..99e0e7ae12e9 100644 > --- a/drivers/pci/of.c > +++ b/drivers/pci/of.c > @@ -826,3 +826,48 @@ 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); > + kerneldoc? Define who should free the memory and how. > +int of_pci_get_equalization_presets(struct device *dev, > + struct pci_eq_presets *presets, > + int num_lanes) > +{ > + char name[20]; > + void **preset; > + void *temp; > + 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; > + } > + } > + > + for (int i = 1; i < sizeof(struct pci_eq_presets) / sizeof(void *); i++) { > + snprintf(name, sizeof(name), "eq-presets-%dgts", 8 << i); > + if (of_property_present(dev->of_node, name)) { > + temp = devm_kzalloc(dev, sizeof(u8) * num_lanes, GFP_KERNEL); > + if (!temp) > + return -ENOMEM; > + > + ret = of_property_read_u8_array(dev->of_node, name, > + temp, num_lanes); > + if (ret) { > + dev_err(dev, "Error %s %d\n", name, ret); > + return ret; > + } > + > + preset = (void **)((u8 *)presets + i * sizeof(void *)); Ugh. > + *preset = temp; > + } > + } > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(of_pci_get_equalization_presets); > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > index 14d00ce45bfa..82362d58bedc 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 { > + void *eq_presets_8gts; > + void *eq_presets_16gts; > + void *eq_presets_32gts; > + void *eq_presets_64gts; Why are all of those void*? 8gts is u16*, all other are u8*. > +}; Empty lines before and after the struct definition. > #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); Keep the empty line. > #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 inline 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; > > -- > 2.34.1 >
diff --git a/drivers/pci/of.c b/drivers/pci/of.c index dacea3fc5128..99e0e7ae12e9 100644 --- a/drivers/pci/of.c +++ b/drivers/pci/of.c @@ -826,3 +826,48 @@ 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) +{ + char name[20]; + void **preset; + void *temp; + 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; + } + } + + for (int i = 1; i < sizeof(struct pci_eq_presets) / sizeof(void *); i++) { + snprintf(name, sizeof(name), "eq-presets-%dgts", 8 << i); + if (of_property_present(dev->of_node, name)) { + temp = devm_kzalloc(dev, sizeof(u8) * num_lanes, GFP_KERNEL); + if (!temp) + return -ENOMEM; + + ret = of_property_read_u8_array(dev->of_node, name, + temp, num_lanes); + if (ret) { + dev_err(dev, "Error %s %d\n", name, ret); + return ret; + } + + preset = (void **)((u8 *)presets + i * sizeof(void *)); + *preset = temp; + } + } + + return 0; +} +EXPORT_SYMBOL_GPL(of_pci_get_equalization_presets); diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index 14d00ce45bfa..82362d58bedc 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 { + void *eq_presets_8gts; + void *eq_presets_16gts; + void *eq_presets_32gts; + void *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 inline 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 <krishna.chundru@oss.qualcomm.com> --- drivers/pci/of.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ drivers/pci/pci.h | 17 +++++++++++++++-- 2 files changed, 60 insertions(+), 2 deletions(-)