| Message ID | 20241223-preset_v2-v3-2-a339f475caf5@oss.qualcomm.com |
|---|---|
| State | New |
| Headers | show |
| Series | PCI: dwc: Add support for configuring lane equalization presets | expand |
On 12/24/2024 12:00 AM, Dmitry Baryshkov wrote: > On Mon, Dec 23, 2024 at 10:13:29PM +0530, Krishna Chaitanya Chundru wrote: >> >> >> On 12/23/2024 8:56 PM, Dmitry Baryshkov wrote: >>> On Mon, Dec 23, 2024 at 08:02:23PM +0530, Krishna Chaitanya Chundru wrote: >>>> >>>> >>>> On 12/23/2024 5:17 PM, Dmitry Baryshkov wrote: >>>>> 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. >>>>> >>>> I will update this in next series. >>>> as we are allocating using devm_kzalloc it should be freed on driver >>>> detach, as no special freeing is required. >>>>>> +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. >>>>> >>>> I was trying iterate over each element on the structure as presets holds the >>>> starting address of the structure and to that we are adding size of the void >>>> * point to go to each element. I did this way to reduce the >>>> redundant code to read all the gts which has same way of storing the data >>>> from the device tree. I will add comments here in the next series. >>> >>> Please rewrite this in a cleaner way. The code shouldn't raise >>> questions. >>> >>>>>> + *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*. >>>>> >>>> To have common parsing logic I moved them to void*, as these are pointers >>>> actual memory is allocated by of_pci_get_equalization_presets() >>>> based upon the gts these should not give any issues. >>> >>> Please, don't. They have types. void pointers are for the opaque data. >>> >> ok. >> >> I think then better to use v1 patch >> https://lore.kernel.org/all/20241116-presets-v1-2-878a837a4fee@quicinc.com/ >> >> konrad, any objection on using v1 as that will be cleaner way even if we >> have some repetitive code. > > Konrad had a nice suggestion about using the array of values. Please use > such an array for 16gts and above. This removes most of repetitive code. > I don't feel having array in the preset structure looks good, I have come up with this logic if you feel it is not so good I will go to the suggested way by having array for 16gts and above. 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 = EQ_PRESET_TYPE_16GTS; i < EQ_PRESET_TYPE_64GTS; 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; } switch (i) { case EQ_PRESET_TYPE_16GTS: presets->eq_presets_16gts = temp; break; case EQ_PRESET_TYPE_32GTS: presets->eq_presets_32gts = temp; break; case EQ_PRESET_TYPE_64GTS: presets->eq_presets_64gts = temp; break; } } } - Krishna Chaitanya. >
On 12/24/2024 3:25 PM, Dmitry Baryshkov wrote: > On Tue, Dec 24, 2024 at 02:47:00PM +0530, Krishna Chaitanya Chundru wrote: >> >> >> On 12/24/2024 12:00 AM, Dmitry Baryshkov wrote: >>> On Mon, Dec 23, 2024 at 10:13:29PM +0530, Krishna Chaitanya Chundru wrote: >>>> >>>> >>>> On 12/23/2024 8:56 PM, Dmitry Baryshkov wrote: >>>>> On Mon, Dec 23, 2024 at 08:02:23PM +0530, Krishna Chaitanya Chundru wrote: >>>>>> >>>>>> >>>>>> On 12/23/2024 5:17 PM, Dmitry Baryshkov wrote: >>>>>>> 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. >>>>>>> >>>>>> I will update this in next series. >>>>>> as we are allocating using devm_kzalloc it should be freed on driver >>>>>> detach, as no special freeing is required. >>>>>>>> +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. >>>>>>> >>>>>> I was trying iterate over each element on the structure as presets holds the >>>>>> starting address of the structure and to that we are adding size of the void >>>>>> * point to go to each element. I did this way to reduce the >>>>>> redundant code to read all the gts which has same way of storing the data >>>>>> from the device tree. I will add comments here in the next series. >>>>> >>>>> Please rewrite this in a cleaner way. The code shouldn't raise >>>>> questions. >>>>> >>>>>>>> + *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*. >>>>>>> >>>>>> To have common parsing logic I moved them to void*, as these are pointers >>>>>> actual memory is allocated by of_pci_get_equalization_presets() >>>>>> based upon the gts these should not give any issues. >>>>> >>>>> Please, don't. They have types. void pointers are for the opaque data. >>>>> >>>> ok. >>>> >>>> I think then better to use v1 patch >>>> https://lore.kernel.org/all/20241116-presets-v1-2-878a837a4fee@quicinc.com/ >>>> >>>> konrad, any objection on using v1 as that will be cleaner way even if we >>>> have some repetitive code. >>> >>> Konrad had a nice suggestion about using the array of values. Please use >>> such an array for 16gts and above. This removes most of repetitive code. >>> >> I don't feel having array in the preset structure looks good, I have >> come up with this logic if you feel it is not so good I will go to the >> suggested way by having array for 16gts and above. >> >> 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 = EQ_PRESET_TYPE_16GTS; i < EQ_PRESET_TYPE_64GTS; 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; >> } >> >> switch (i) { >> case EQ_PRESET_TYPE_16GTS: >> presets->eq_presets_16gts = temp; >> break; >> case EQ_PRESET_TYPE_32GTS: >> presets->eq_presets_32gts = temp; >> break; >> case EQ_PRESET_TYPE_64GTS: >> presets->eq_presets_64gts = temp; >> break; >> } > > This looks like 'presets->eq_presets[i] = temp;', but I won't insist on > that. > > Also, a strange thought came to my mind: we know that there won't be > more than 16 lanes. Can we have the following structure instead: > > #define MAX_LANES 16 > enum pcie_gts { > PCIE_GTS_16GTS, > PCIE_GTS_32GTS, > PCIE_GTS_64GTS, > PCIE_GTS_MAX, > }; > struct pci_eq_presets { > u16 eq_presets_8gts[MAX_LANES]; > u8 eq_presets_Ngts[PCIE_GTS_MAX][MAX_LANES]; > }; > > This should allow you to drop the of_property_present() and > devm_kzalloc(). Just read DT data into a corresponding array. > in the dwc driver patch I was using pointers and memory allocation to known if the property is present or not. If I use this way I might end up reading dt property again. I think better to switch to have a array for above 16gts. - Krishna Chaitanya. >> } >> } >> - Krishna Chaitanya. >> >>> >
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(-)