Message-ID: <6a038c5f-1632-4a5e-aadb-0b5dd94236f9@cixtech.com>
Date: Fri, 15 Aug 2025 15:53:31 +0800
From: Hans Zhang <hans.zhang@...tech.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: bhelgaas@...gle.com, lpieralisi@...nel.org, kw@...ux.com,
 mani@...nel.org, robh@...nel.org, kwilczynski@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, mpillai@...ence.com,
 fugang.duan@...tech.com, guoyin.chen@...tech.com, peter.chen@...tech.com,
 cix-kernel-upstream@...tech.com, linux-pci@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 10/13] PCI: sky1: Add PCIe host support for CIX Sky1



On 2025/8/15 06:46, Bjorn Helgaas wrote:
> EXTERNAL EMAIL
> 
> On Wed, Aug 13, 2025 at 12:23:28PM +0800, hans.zhang@...tech.com wrote:
>> From: Hans Zhang <hans.zhang@...tech.com>
>>
>> Add driver for the CIX Sky1 SoC PCIe Gen4 16 GT/s controller based
>> on the Cadence PCIe core.
>>
>> Supports MSI/MSI-x via GICv3, Single Virtual Channel, Single Function.
> 
>> +config PCI_SKY1_HOST
>> +     tristate "CIX SKY1 PCIe controller (host mode)"
>> +     depends on OF
>> +     select PCIE_CADENCE_HOST
>> +     select PCI_ECAM
>> +     help
>> +       Say Y here if you want to support the CIX SKY1 PCIe platform
>> +       controller in host mode. CIX SKY1 PCIe controller uses Cadence HPA(High
>> +       Performance Architecture IP[Second generation of cadence PCIe IP])
>> +
>> +       This driver requires Cadence PCIe core infrastructure (PCIE_CADENCE_HOST)
>> +       and hardware platform adaptation layer to function.
> 
> Reorder so this menu entry appears in alphabetical order by vendor.
> 
> Add space in "HPA(..".
> 
> Add space in "IP[Second ..."
> 
> s/cadence PCIe IP/Cadence PCIe IP/
> 
> Rewrap so help text fits in 80 columns when displayed by menuconfig.

Dear Bjorn,

Thank you very much for your reply. Will change.

> 
>> +++ b/drivers/pci/controller/cadence/Makefile
>> +++ b/drivers/pci/controller/cadence/pci-sky1.c
>> @@ -0,0 +1,294 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * PCIe controller driver for CIX's sky1 SoCs
>> + *
>> + * Author: Hans Zhang <hans.zhang@...tech.com>
>> + */
> 
> The typical comment style, thank you :)
> 
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/of_device.h>
>> +#include <linux/pci.h>
>> +#include <linux/pci-ecam.h>
>> +#include <linux/pci_ids.h>
>> +
>> +#include "pcie-cadence.h"
>> +#include "pcie-cadence-host-common.h"
>> +
>> +#define STRAP_REG(n) ((n) * 0x04)
>> +#define STATUS_REG(n) ((n) * 0x04)
>> +
>> +#define RCSU_STRAP_REG 0x300
>> +#define RCSU_STATUS_REG 0x400
>> +
>> +#define SKY1_IP_REG_BANK_OFFSET 0x1000
>> +#define SKY1_IP_CFG_CTRL_REG_BANK_OFFSET 0x4c00
>> +#define SKY1_IP_AXI_MASTER_COMMON_OFFSET 0xf000
>> +#define SKY1_AXI_SLAVE_OFFSET 0x9000
>> +#define SKY1_AXI_MASTER_OFFSET 0xb000
>> +#define SKY1_AXI_HLS_REGISTERS_OFFSET 0xc000
>> +#define SKY1_AXI_RAS_REGISTERS_OFFSET 0xe000
>> +#define SKY1_DTI_REGISTERS_OFFSET 0xd000
> 
> Indent the values to line up.
> 
> Consider dropping "_OFFSET".

Will change.

> 
>> +#define IP_REG_I_DBG_STS_0 0x420
>> +
>> +#define LINK_TRAINING_ENABLE BIT(0)
>> +#define LINK_COMPLETE BIT(0)
> 
> Define next to the offset of the register that contains these.
> Consider naming them to relate to the register.
> 

All of our registers are RCSU (Remote CIX System Unit registers.), and 
they are named like this: I moved it below this.
#define STRAP_REG(n) ((n) * 0x04)
#define STATUS_REG(n) ((n) * 0x04)

>> +enum cix_soc_type {
>> +     CIX_SKY1,
>> +};
>> +
>> +struct sky1_pcie_data {
>> +     struct cdns_plat_pcie_of_data reg_off;
> 
> Weird name for this member.  cdns_plat_pcie_of_data contains more than
> just offsets.

We are considering deleting cdns_plat_pcie_of_data. Krzysztof also 
provided a review opinion, intending to directly assign the register 
offset value in the probe.

> 
>> +     enum cix_soc_type soc_type;
>> +};
>> +
>> +struct sky1_pcie {
>> +     struct device *dev;
>> +     const struct sky1_pcie_data *data;
>> +     struct cdns_pcie *cdns_pcie;
> 
> Typically first in the driver struct.  Also cdns_pcie already contains
> a struct device *; do you need another?

I checked and it's indeed possible to delete it by using "dev" in cdns_pcie.

> 
>> +     struct cdns_pcie_rc *cdns_pcie_rc;
>> +
>> +     struct resource *cfg_res;
>> +     struct resource *msg_res;
>> +     struct pci_config_window *cfg;
>> +     void __iomem *rcsu_base;
>> +     void __iomem *strap_base;
>> +     void __iomem *status_base;
>> +     void __iomem *reg_base;
>> +     void __iomem *cfg_base;
>> +     void __iomem *msg_base;
>> +};
>> +
>> +static void sky1_pcie_clear_and_set_dword(void __iomem *addr, u32 clear,
>> +                                       u32 set)
>> +{
>> +     u32 val;
>> +
>> +     val = readl(addr);
>> +     val &= ~clear;
>> +     val |= set;
>> +     writel(val, addr);
> 
> Nothing specific to sky1 here.  Find an existing interface or copy the
> style of other drivers.  Surely other drivers do something similar,
> but "git grep clear_and_set_dword drivers/pci/controller/" finds
> nothing.

My original intention was for the future upstream, as there are many 
repetitive read and write registers. Then I'll delete it first.

> 
>> +static int sky1_pcie_parse_mem(struct sky1_pcie *pcie)
>> +{
>> +     struct device *dev = pcie->dev;
>> +     struct platform_device *pdev = to_platform_device(dev);
>> +     struct resource *res;
>> +     void __iomem *base;
>> +     int ret = 0;
>> +
>> +     base = devm_platform_ioremap_resource_byname(pdev, "reg");
>> +     if (IS_ERR(base)) {
>> +             dev_err(dev, "Parse \"reg\" resource err\n");
>> +             return PTR_ERR(base);
>> +     }
>> +     pcie->reg_base = base;
>> +
>> +     res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "cfg");
>> +     if (!res) {
>> +             dev_err(dev, "Parse \"cfg\" resource err\n");
>> +             return -ENXIO;
>> +     }
>> +     pcie->cfg_res = res;
>> +
>> +     res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "rcsu");
>> +     if (!res) {
>> +             dev_err(dev, "Parse \"rcsu\" resource err\n");
>> +             return -ENXIO;
>> +     }
>> +     pcie->rcsu_base = devm_ioremap(dev, res->start, resource_size(res));
>> +     if (!pcie->rcsu_base) {
>> +             dev_err(dev, "ioremap failed for resource %pR\n", res);
>> +             return -ENOMEM;
>> +     }
>> +
>> +     res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "msg");
>> +     if (!res) {
>> +             dev_err(dev, "Parse \"msg\" resource err\n");
>> +             return -ENXIO;
>> +     }
>> +     pcie->msg_res = res;
>> +     pcie->msg_base = devm_ioremap(dev, res->start, resource_size(res));
>> +     if (!pcie->msg_base) {
>> +             dev_err(dev, "ioremap failed for resource %pR\n", res);
>> +             return -ENOMEM;
>> +     }
>> +
>> +     return ret;
> 
> "ret" is never used; remove it and just "return 0" here.

Will change.

> 
>> +}
>> +
>> +static int sky1_pcie_parse_property(struct platform_device *pdev,
>> +                                 struct sky1_pcie *pcie)
> 
> Find a similar function in other drivers and copy the name.
> "git grep parse_property drivers/pci/controller/" finds nothing.

Will change.

> 
>> +{
>> +     int ret = 0;
>> +
>> +     ret = sky1_pcie_parse_mem(pcie);
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     sky1_pcie_init_bases(pcie);
>> +
>> +     return ret;
> 
> Drop "ret" and return 0 here.

Will change.

> 
>> +}
>> +
>> +static int sky1_pcie_start_link(struct cdns_pcie *cdns_pcie)
>> +{
>> +     struct sky1_pcie *pcie = dev_get_drvdata(cdns_pcie->dev);
>> +
>> +     sky1_pcie_clear_and_set_dword(pcie->strap_base + STRAP_REG(1),
>> +                                   0, LINK_TRAINING_ENABLE);
>> +
>> +     return 0;
>> +}
>> +
>> +static void sky1_pcie_stop_link(struct cdns_pcie *cdns_pcie)
>> +{
>> +     struct sky1_pcie *pcie = dev_get_drvdata(cdns_pcie->dev);
>> +
>> +     sky1_pcie_clear_and_set_dword(pcie->strap_base + STRAP_REG(1),
>> +                                   LINK_TRAINING_ENABLE, 0);
>> +}
>> +
>> +
>> +static bool sky1_pcie_link_up(struct cdns_pcie *cdns_pcie)
>> +{
>> +     u32 val;
>> +
>> +     val = cdns_pcie_hpa_readl(cdns_pcie, REG_BANK_IP_REG,
>> +                               IP_REG_I_DBG_STS_0);
>> +     return val & LINK_COMPLETE;
>> +}
>> +
>> +static const struct cdns_pcie_ops sky1_pcie_ops = {
>> +     .start_link = sky1_pcie_start_link,
>> +     .stop_link = sky1_pcie_stop_link,
>> +     .link_up = sky1_pcie_link_up,
>> +};
>> +
>> +static int sky1_pcie_probe(struct platform_device *pdev)
>> +{
>> +     const struct sky1_pcie_data *data;
>> +     struct device *dev = &pdev->dev;
>> +     struct pci_host_bridge *bridge;
>> +     struct cdns_pcie *cdns_pcie;
>> +     struct resource_entry *bus;
>> +     struct cdns_pcie_rc *rc;
>> +     struct sky1_pcie *pcie;
>> +     int ret;
>> +
>> +     pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
>> +     if (!pcie)
>> +             return -ENOMEM;
>> +
>> +     data = of_device_get_match_data(dev);
>> +     if (!data)
>> +             return -EINVAL;
>> +
>> +     pcie->data = data;
>> +     pcie->dev = dev;
>> +     dev_set_drvdata(dev, pcie);
>> +
>> +     bridge = devm_pci_alloc_host_bridge(dev, sizeof(*rc));
>> +     if (!bridge)
>> +             return -ENOMEM;
>> +
>> +     bus = resource_list_first_type(&bridge->windows, IORESOURCE_BUS);
>> +     if (!bus)
>> +             return -ENODEV;
> 
> Maybe put this near the code that uses it instead of sticking the
> unrelated sky1_pcie_parse_property() in the middle?

Will change.

> 
>> +     ret = sky1_pcie_parse_property(pdev, pcie);
>> +     if (ret < 0)
>> +             return -ENXIO;
>> +
>> +     pcie->cfg = pci_ecam_create(dev, pcie->cfg_res, bus->res,
>> +                                 &pci_generic_ecam_ops);
>> +     if (IS_ERR(pcie->cfg))
>> +             return PTR_ERR(pcie->cfg);
>> +
>> +     bridge->ops = (struct pci_ops *)&pci_generic_ecam_ops.pci_ops;
>> +     rc = pci_host_bridge_priv(bridge);
>> +     rc->ecam_support_flag = 1;
>> +     rc->cfg_base = pcie->cfg->win;
>> +     rc->cfg_res = &pcie->cfg->res;
>> +
>> +     cdns_pcie = &rc->pcie;
>> +     cdns_pcie->dev = dev;
>> +     cdns_pcie->ops = &sky1_pcie_ops;
>> +     cdns_pcie->reg_base = pcie->reg_base;
>> +     cdns_pcie->msg_res = pcie->msg_res;
>> +     cdns_pcie->cdns_pcie_reg_offsets = &data->reg_off;
>> +     cdns_pcie->is_rc = data->reg_off.is_rc;
>> +
>> +     pcie->cdns_pcie = cdns_pcie;
>> +     pcie->cdns_pcie_rc = rc;
>> +     pcie->cfg_base = rc->cfg_base;
>> +     bridge->sysdata = pcie->cfg;
>> +
>> +     if (data->soc_type == CIX_SKY1) {
>> +             rc->vendor_id = PCI_VENDOR_ID_CIX;
>> +             rc->device_id = PCI_DEVICE_ID_CIX_SKY1;
>> +             rc->no_inbound_flag = 1;
>> +     }
>> +
>> +     ret = cdns_pcie_hpa_host_setup(rc);
>> +     if (ret < 0) {
>> +             pci_ecam_free(pcie->cfg);
>> +             return ret;
>> +     }
>> +
>> +     return 0;
>> +}
>> +
>> +static const struct sky1_pcie_data sky1_pcie_rc_data = {
>> +     .reg_off = {
>> +             .is_rc = true,
>> +             .ip_reg_bank_offset = SKY1_IP_REG_BANK_OFFSET,
>> +             .ip_cfg_ctrl_reg_offset = SKY1_IP_CFG_CTRL_REG_BANK_OFFSET,
>> +             .axi_mstr_common_offset = SKY1_IP_AXI_MASTER_COMMON_OFFSET,
>> +             .axi_slave_offset = SKY1_AXI_SLAVE_OFFSET,
>> +             .axi_master_offset = SKY1_AXI_MASTER_OFFSET,
>> +             .axi_hls_offset = SKY1_AXI_HLS_REGISTERS_OFFSET,
>> +             .axi_ras_offset = SKY1_AXI_RAS_REGISTERS_OFFSET,
>> +             .axi_dti_offset = SKY1_DTI_REGISTERS_OFFSET,
>> +     },
>> +     .soc_type = CIX_SKY1,
>> +};
>> +
>> +static const struct of_device_id of_sky1_pcie_match[] = {
>> +     {
>> +             .compatible = "cix,sky1-pcie-host",
>> +             .data = &sky1_pcie_rc_data,
>> +     },
>> +     {},
>> +};
>> +
>> +static void sky1_pcie_remove(struct platform_device *pdev)
>> +{
>> +     struct sky1_pcie *pcie = platform_get_drvdata(pdev);
>> +
>> +     pci_ecam_free(pcie->cfg);
>> +}
>> +
>> +static struct platform_driver sky1_pcie_driver = {
>> +     .probe  = sky1_pcie_probe,
>> +     .remove = sky1_pcie_remove,
>> +     .driver = {
>> +             .name = "sky1-pcie",
>> +             .of_match_table = of_sky1_pcie_match,
>> +     },
>> +};
>> +module_platform_driver(sky1_pcie_driver);
>> +
>> +MODULE_LICENSE("GPL");
>> +MODULE_DESCRIPTION("PCIe controller driver for CIX's sky1 SoCs");
>> +MODULE_AUTHOR("Hans Zhang <hans.zhang@...tech.com>");
>> --
>> 2.49.0
>>

Best regards,
Hans

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