Re: [PATCH v2 2/5] PCI: stm32: Add PCIe host support for STM32MP25

Manivannan Sadhasivam
2024-12-03T14:54:11Z

On Tue, Nov 26, 2024 at 04:51:16PM +0100, Christian Bruel wrote:
> Add driver for the STM32MP25 SoC PCIe Gen2 controller based on the
> DesignWare PCIe core.
>
> Supports MSI via GICv2m, Single Virtual Channel, Single Function
>
> Signed-off-by: Christian Bruel <christian.bruel@foss.st.com>
> ---
> drivers/pci/controller/dwc/Kconfig | 12 +
> drivers/pci/controller/dwc/Makefile | 1 +
> drivers/pci/controller/dwc/pcie-stm32.c | 402 ++++++++++++++++++++++++
> drivers/pci/controller/dwc/pcie-stm32.h | 15 +
> 4 files changed, 430 insertions(+)
> create mode 100644 drivers/pci/controller/dwc/pcie-stm32.c
> create mode 100644 drivers/pci/controller/dwc/pcie-stm32.h
>
> diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
> index b6d6778b0698..0c18879b604c 100644
> --- a/drivers/pci/controller/dwc/Kconfig
> +++ b/drivers/pci/controller/dwc/Kconfig
> @@ -389,6 +389,18 @@ config PCIE_SPEAR13XX
> help
> Say Y here if you want PCIe support on SPEAr13XX SoCs.
>
> +config PCIE_STM32
> + tristate "STMicroelectronics STM32MP25 PCIe Controller (host mode)"
> + depends on ARCH_STM32 || COMPILE_TEST
> + depends on PCI_MSI
> + select PCIE_DW_HOST
> + help
> + Enables support for the DesignWare core based PCIe host controller
> + found in STM32MP25 SoC.
> +
> + This driver can also be built as a module. If so, the module
> + will be called pcie-stm32.
> +
> config PCI_DRA7XX
> tristate
>
> diff --git a/drivers/pci/controller/dwc/Makefile b/drivers/pci/controller/dwc/Makefile
> index a8308d9ea986..576d99cb3bc5 100644
> --- a/drivers/pci/controller/dwc/Makefile
> +++ b/drivers/pci/controller/dwc/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_PCIE_UNIPHIER) += pcie-uniphier.o
> obj-$(CONFIG_PCIE_UNIPHIER_EP) += pcie-uniphier-ep.o
> obj-$(CONFIG_PCIE_VISCONTI_HOST) += pcie-visconti.o
> obj-$(CONFIG_PCIE_RCAR_GEN4) += pcie-rcar-gen4.o
> +obj-$(CONFIG_PCIE_STM32) += pcie-stm32.o
>
> # The following drivers are for devices that use the generic ACPI
> # pci_root.c driver but don't support standard ECAM config access.
> diff --git a/drivers/pci/controller/dwc/pcie-stm32.c b/drivers/pci/controller/dwc/pcie-stm32.c
> new file mode 100644
> index 000000000000..fa787406c0e4
> --- /dev/null
> +++ b/drivers/pci/controller/dwc/pcie-stm32.c
> @@ -0,0 +1,402 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * STMicroelectronics STM32MP25 PCIe root complex driver.
> + *
> + * Copyright (C) 2024 STMicroelectronics
> + * Author: Christian Bruel <christian.bruel@foss.st.com>
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/of_platform.h>
> +#include <linux/phy/phy.h>
> +#include <linux/pinctrl/devinfo.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/reset.h>
> +#include "pcie-designware.h"
> +#include "pcie-stm32.h"
> +#include "../../pci.h"
> +
> +struct stm32_pcie {
> + struct dw_pcie *pci;
> + struct regmap *regmap;
> + struct reset_control *rst;
> + struct phy *phy;
> + struct clk *clk;
> + struct gpio_desc *perst_gpio;
> + struct gpio_desc *wake_gpio;
> + unsigned int wake_irq;
> + bool link_is_up;
> +};
> +
> +static int stm32_pcie_start_link(struct dw_pcie *pci)
> +{
> + struct stm32_pcie *stm32_pcie = to_stm32_pcie(pci);
> + u32 ret;
> +
> + if (stm32_pcie->perst_gpio) {

gpiod_set_value() will bail out if 'perst_gpio' is NULL. So no need to add a
check.

> + /* Make sure PERST# is asserted. */

Why?

> + gpiod_set_value(stm32_pcie->perst_gpio, 1);
> +
> + fsleep(PCIE_T_PERST_CLK_US);
> + gpiod_set_value(stm32_pcie->perst_gpio, 0);

Why can't you deassert PERST# in stm32_add_pcie_port()?

> + }
> +
> + ret = regmap_update_bits(stm32_pcie->regmap, SYSCFG_PCIECR,
> + STM32MP25_PCIECR_LTSSM_EN,
> + STM32MP25_PCIECR_LTSSM_EN);
> +
> + if (stm32_pcie->perst_gpio)

It doesn't hurt to call msleep() always.

> + msleep(PCIE_T_RRS_READY_MS);
> +
> + return ret;
> +}
> +
> +static void stm32_pcie_stop_link(struct dw_pcie *pci)
> +{
> + struct stm32_pcie *stm32_pcie = to_stm32_pcie(pci);
> +
> + regmap_update_bits(stm32_pcie->regmap, SYSCFG_PCIECR,
> + STM32MP25_PCIECR_LTSSM_EN, 0);
> +
> + /* Assert PERST# */
> + if (stm32_pcie->perst_gpio)
> + gpiod_set_value(stm32_pcie->perst_gpio, 1);

I don't like tying PERST# handling with start/stop link. PERST# should be
handled based on the power/clock state.

> +}
> +
> +static int stm32_pcie_suspend(struct device *dev)
> +{
> + struct stm32_pcie *stm32_pcie = dev_get_drvdata(dev);
> +
> + if (device_may_wakeup(dev) || device_wakeup_path(dev))
> + enable_irq_wake(stm32_pcie->wake_irq);
> +
> + return 0;
> +}
> +
> +static int stm32_pcie_resume(struct device *dev)
> +{
> + struct stm32_pcie *stm32_pcie = dev_get_drvdata(dev);
> +
> + if (device_may_wakeup(dev) || device_wakeup_path(dev))
> + disable_irq_wake(stm32_pcie->wake_irq);
> +
> + return 0;
> +}
> +
> +static int stm32_pcie_suspend_noirq(struct device *dev)
> +{
> + struct stm32_pcie *stm32_pcie = dev_get_drvdata(dev);
> +
> + stm32_pcie->link_is_up = dw_pcie_link_up(stm32_pcie->pci);
> +
> + stm32_pcie_stop_link(stm32_pcie->pci);

I don't understand how endpoint can wakeup the host if PERST# gets asserted.

> + clk_disable_unprepare(stm32_pcie->clk);
> +
> + if (!device_may_wakeup(dev) && !device_wakeup_path(dev))
> + phy_exit(stm32_pcie->phy);
> +
> + return pinctrl_pm_select_sleep_state(dev);
> +}
> +
> +static int stm32_pcie_resume_noirq(struct device *dev)
> +{
> + struct stm32_pcie *stm32_pcie = dev_get_drvdata(dev);
> + struct dw_pcie *pci = stm32_pcie->pci;
> + struct dw_pcie_rp *pp = &pci->pp;
> + int ret;
> +
> + /* init_state must be called first to force clk_req# gpio when no

CLKREQ#

Why RC should control CLKREQ#?

Also please use preferred style for multi-line comments:

/*
* ...
*/

> + * device is plugged.
> + */
> + if (!IS_ERR(dev->pins->init_state))
> + ret = pinctrl_select_state(dev->pins->p, dev->pins->init_state);
> + else
> + ret = pinctrl_pm_select_default_state(dev);
> +
> + if (ret) {
> + dev_err(dev, "Failed to activate pinctrl pm state: %d\n", ret);
> + return ret;
> + }
> +
> + if (!device_may_wakeup(dev) && !device_wakeup_path(dev)) {
> + ret = phy_init(stm32_pcie->phy);
> + if (ret) {
> + pinctrl_pm_select_default_state(dev);
> + return ret;
> + }
> + }
> +
> + ret = clk_prepare_enable(stm32_pcie->clk);
> + if (ret)
> + goto clk_err;

Please name the goto labels of their purpose. Like err_phy_exit.

> +
> + ret = dw_pcie_setup_rc(pp);
> + if (ret)
> + goto pcie_err;

This should be, 'err_disable_clk'.

> +
> + if (stm32_pcie->link_is_up) {

Why do you need this check? You cannot start the link in the absence of an
endpoint?

> + ret = stm32_pcie_start_link(stm32_pcie->pci);
> + if (ret)
> + goto pcie_err;
> +
> + /* Ignore errors, the link may come up later */
> + dw_pcie_wait_for_link(stm32_pcie->pci);
> + }
> +
> + pinctrl_pm_select_default_state(dev);
> +
> + return 0;
> +
> +pcie_err:
> + dw_pcie_host_deinit(pp);
> + clk_disable_unprepare(stm32_pcie->clk);
> +clk_err:
> + phy_exit(stm32_pcie->phy);
> + pinctrl_pm_select_default_state(dev);
> +
> + return ret;
> +}
> +
> +static const struct dev_pm_ops stm32_pcie_pm_ops = {
> + NOIRQ_SYSTEM_SLEEP_PM_OPS(stm32_pcie_suspend_noirq,
> + stm32_pcie_resume_noirq)

Can you make use of dw_pcie_{suspend/resume}_noirq() APIs?

> + SYSTEM_SLEEP_PM_OPS(stm32_pcie_suspend, stm32_pcie_resume)
> +};
> +
> +static const struct dw_pcie_host_ops stm32_pcie_host_ops = {
> +};
> +
> +static const struct dw_pcie_ops dw_pcie_ops = {
> + .start_link = stm32_pcie_start_link,
> + .stop_link = stm32_pcie_stop_link
> +};
> +

[...]

> + if (device_property_read_bool(dev, "wakeup-source")) {
> + stm32_pcie->wake_gpio = devm_gpiod_get_optional(dev, "wake",
> + GPIOD_IN);
> + if (IS_ERR(stm32_pcie->wake_gpio))
> + return dev_err_probe(dev, PTR_ERR(stm32_pcie->wake_gpio),
> + "Failed to get wake GPIO\n");
> + }
> +
> + if (stm32_pcie->wake_gpio) {
> + stm32_pcie->wake_irq = gpiod_to_irq(stm32_pcie->wake_gpio);
> +
> + ret = devm_request_threaded_irq(&pdev->dev,
> + stm32_pcie->wake_irq, NULL,
> + stm32_pcie_wake_irq_handler,
> + IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
> + "wake_irq", stm32_pcie);
> +
> + if (ret)
> + return dev_err_probe(dev, ret, "Failed to request WAKE IRQ: %d\n", ret);
> + }

Can we move WAKE# gpio handling to DWC core? There is nothing STM32 specific
here.

> +
> + ret = devm_pm_runtime_enable(dev);
> + if (ret < 0) {
> + dev_err(dev, "Failed to enable runtime PM %d\n", ret);
> + return ret;
> + }
> +
> + ret = pm_runtime_resume_and_get(dev);
> + if (ret < 0) {
> + dev_err(dev, "Failed to get runtime PM %d\n", ret);
> + return ret;
> + }
> +
> + ret = stm32_add_pcie_port(stm32_pcie, pdev);
> + if (ret) {
> + pm_runtime_put_sync(&pdev->dev);
> + return ret;
> + }
> +
> + if (stm32_pcie->wake_gpio)
> + device_set_wakeup_capable(dev, true);
> +
> + return 0;
> +}
> +
> +static void stm32_pcie_remove(struct platform_device *pdev)
> +{
> + struct stm32_pcie *stm32_pcie = platform_get_drvdata(pdev);
> + struct dw_pcie_rp *pp = &stm32_pcie->pci->pp;
> +
> + if (stm32_pcie->wake_gpio)
> + device_init_wakeup(&pdev->dev, false);
> +
> + dw_pcie_host_deinit(pp);
> + clk_disable_unprepare(stm32_pcie->clk);
> +
> + phy_exit(stm32_pcie->phy);
> +
> + pm_runtime_put_sync(&pdev->dev);
> +}
> +
> +static const struct of_device_id stm32_pcie_of_match[] = {
> + { .compatible = "st,stm32mp25-pcie-rc" },
> + {},
> +};
> +
> +static struct platform_driver stm32_pcie_driver = {
> + .probe = stm32_pcie_probe,
> + .remove = stm32_pcie_remove,
> + .driver = {
> + .name = "stm32-pcie",
> + .of_match_table = stm32_pcie_of_match,
> + .pm = &stm32_pcie_pm_ops,

Just use a single space instead of tab.

Could you also set PROBE_PREFER_ASYNCHRONOUS to allow async probing of
controller drivers?

> + },
> +};
> +
> +static bool is_stm32_pcie_driver(struct device *dev)
> +{
> + /* PCI bridge */
> + dev = get_device(dev);
> +
> + /* Platform driver */
> + dev = get_device(dev->parent);
> +
> + return (dev->driver == &stm32_pcie_driver.driver);
> +}
> +
> +/*
> + * DMA masters can only access the first 4GB of memory space,
> + * so we setup the bus DMA limit accordingly.
> + */
> +static int stm32_dma_limit(struct pci_dev *pdev, void *data)
> +{
> + dev_dbg(&pdev->dev, "disabling DMA DAC for device");
> +
> + pdev->dev.bus_dma_limit = DMA_BIT_MASK(32);
> +
> + return 0;
> +}
> +
> +static void quirk_stm32_dma_mask(struct pci_dev *pci)
> +{
> + struct pci_dev *root_port;
> +
> + root_port = pcie_find_root_port(pci);
> +
> + if (root_port && is_stm32_pcie_driver(root_port->dev.parent))
> + pci_walk_bus(pci->bus, stm32_dma_limit, NULL);
> +}
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_SYNOPSYS, 0x0550, quirk_stm32_dma_mask);

This is not the correct way of using DMA masks as Bjorn noted.

- Mani

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