[PATCH v5 4/9 RESEND] PCI: stm32: Add PCIe Endpoint support for STM32MP25
Christian Bruel
christian.bruel at foss.st.com
Fri Apr 11 08:55:21 PDT 2025
On 4/9/25 10:03, Manivannan Sadhasivam wrote:
> On Tue, Mar 25, 2025 at 07:59:30AM +0100, Christian Bruel wrote:
>> Add driver to configure the STM32MP25 SoC PCIe Gen1 2.5GT/s or Gen2 5GT/s
>> controller based on the DesignWare PCIe core in endpoint mode.
>>
>> Uses the common reference clock provided by the host.
>>
>> The PCIe core_clk receives the pipe0_clk from the ComboPHY as input,
>> and the ComboPHY PLL must be locked for pipe0_clk to be ready.
>> Consequently, PCIe core registers cannot be accessed until the ComboPHY is
>> fully initialised and refclk is enabled and ready.
>>
>> Signed-off-by: Christian Bruel <christian.bruel at foss.st.com>
>> ---
>> drivers/pci/controller/dwc/Kconfig | 12 +
>> drivers/pci/controller/dwc/Makefile | 1 +
>> drivers/pci/controller/dwc/pcie-stm32-ep.c | 420 +++++++++++++++++++++
>> drivers/pci/controller/dwc/pcie-stm32.h | 1 +
>> 4 files changed, 434 insertions(+)
>> create mode 100644 drivers/pci/controller/dwc/pcie-stm32-ep.c
>>
>> diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
>> index 0c18879b604c..4a3eb838557c 100644
>> --- a/drivers/pci/controller/dwc/Kconfig
>> +++ b/drivers/pci/controller/dwc/Kconfig
>> @@ -401,6 +401,18 @@ config PCIE_STM32
>> This driver can also be built as a module. If so, the module
>> will be called pcie-stm32.
>>
>> +config PCIE_STM32_EP
>> + tristate "STMicroelectronics STM32MP25 PCIe Controller (endpoint mode)"
>> + depends on ARCH_STM32 || COMPILE_TEST
>> + depends on PCI_ENDPOINT
>> + select PCIE_DW_EP
>> + help
>> + Enables endpoint support for DesignWare core based PCIe controller
>> + found in STM32MP25 SoC.
>> +
>> + This driver can also be built as a module. If so, the module
>> + will be called pcie-stm32-ep.
>> +
>> config PCI_DRA7XX
>> tristate
>>
>> diff --git a/drivers/pci/controller/dwc/Makefile b/drivers/pci/controller/dwc/Makefile
>> index 576d99cb3bc5..caebd98f6dd3 100644
>> --- a/drivers/pci/controller/dwc/Makefile
>> +++ b/drivers/pci/controller/dwc/Makefile
>> @@ -29,6 +29,7 @@ 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
>> +obj-$(CONFIG_PCIE_STM32_EP) += pcie-stm32-ep.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-ep.c b/drivers/pci/controller/dwc/pcie-stm32-ep.c
>> new file mode 100644
>> index 000000000000..a8e9c5a9b127
>> --- /dev/null
>> +++ b/drivers/pci/controller/dwc/pcie-stm32-ep.c
>> @@ -0,0 +1,420 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * STMicroelectronics STM32MP25 PCIe endpoint driver.
>> + *
>> + * Copyright (C) 2025 STMicroelectronics
>> + * Author: Christian Bruel <christian.bruel at foss.st.com>
>> + */
>> +
>> +#include <linux/clk.h>
>> +#include <linux/mfd/syscon.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/of_gpio.h>
>> +#include <linux/phy/phy.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/pm_runtime.h>
>> +#include <linux/regmap.h>
>> +#include <linux/reset.h>
>> +#include "pcie-designware.h"
>> +#include "pcie-stm32.h"
>> +
>> +enum stm32_pcie_ep_link_status {
>> + STM32_PCIE_EP_LINK_DISABLED,
>> + STM32_PCIE_EP_LINK_ENABLED,
>> +};
>> +
>> +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;
>> + enum stm32_pcie_ep_link_status link_status;
>> + unsigned int perst_irq;
>> +};
>> +
>> +static void stm32_pcie_ep_init(struct dw_pcie_ep *ep)
>> +{
>> + struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>> + enum pci_barno bar;
>> +
>> + for (bar = 0; bar < PCI_STD_NUM_BARS; bar++)
>> + dw_pcie_ep_reset_bar(pci, bar);
>> +}
>> +
>> +static int stm32_pcie_enable_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,
>> + STM32MP25_PCIECR_LTSSM_EN);
>> +
>> + return dw_pcie_wait_for_link(pci);
>> +}
>> +
>> +static void stm32_pcie_disable_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);
>> +}
>> +
>> +static int stm32_pcie_start_link(struct dw_pcie *pci)
>> +{
>> + struct stm32_pcie *stm32_pcie = to_stm32_pcie(pci);
>> + struct dw_pcie_ep *ep = &pci->ep;
>> + int ret;
>> +
>> + if (stm32_pcie->link_status == STM32_PCIE_EP_LINK_ENABLED) {
>> + dev_dbg(pci->dev, "Link is already enabled\n");
>> + return 0;
>> + }
>> +
>> + ret = stm32_pcie_enable_link(pci);
>> + if (ret) {
>> + dev_err(pci->dev, "PCIe cannot establish link: %d\n", ret);
>> + return ret;
>> + }
>> +
>> + dw_pcie_ep_linkup(ep);
>> +
>
> This callback should only be used when the epc_features::linkup_notifier flag is
> set. That only applies to platforms supporting LINK_UP interrupt. In this case,
> once the start_link() callback returns, it is assumed that the link is active.
> So no need to call dw_pcie_ep_linkup().
OK thank you
>
>> + stm32_pcie->link_status = STM32_PCIE_EP_LINK_ENABLED;
>> +
>> + enable_irq(stm32_pcie->perst_irq);
>> +
>> + return 0;
>> +}
>> +
>> +static void stm32_pcie_stop_link(struct dw_pcie *pci)
>> +{
>> + struct stm32_pcie *stm32_pcie = to_stm32_pcie(pci);
>> +
>> + if (stm32_pcie->link_status == STM32_PCIE_EP_LINK_DISABLED) {
>> + dev_dbg(pci->dev, "Link is already disabled\n");
>> + return;
>> + }
>> +
>> + disable_irq(stm32_pcie->perst_irq);
>> +
>> + stm32_pcie_disable_link(pci);
>> +
>> + stm32_pcie->link_status = STM32_PCIE_EP_LINK_DISABLED;
>> +}
>> +
>> +static int stm32_pcie_raise_irq(struct dw_pcie_ep *ep, u8 func_no,
>> + unsigned int type, u16 interrupt_num)
>> +{
>> + struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>> +
>> + switch (type) {
>> + case PCI_IRQ_INTX:
>> + return dw_pcie_ep_raise_intx_irq(ep, func_no);
>> + case PCI_IRQ_MSI:
>> + return dw_pcie_ep_raise_msi_irq(ep, func_no, interrupt_num);
>> + default:
>> + dev_err(pci->dev, "UNKNOWN IRQ type\n");
>> + return -EINVAL;
>> + }
>> +}
>> +
>> +static const struct pci_epc_features stm32_pcie_epc_features = {
>> + .msi_capable = true,
>> + .align = SZ_64K,
>> +};
>> +
>> +static const struct pci_epc_features*
>> +stm32_pcie_get_features(struct dw_pcie_ep *ep)
>> +{
>> + return &stm32_pcie_epc_features;
>> +}
>> +
>> +static const struct dw_pcie_ep_ops stm32_pcie_ep_ops = {
>> + .init = stm32_pcie_ep_init,
>> + .raise_irq = stm32_pcie_raise_irq,
>> + .get_features = stm32_pcie_get_features,
>> +};
>> +
>> +static const struct dw_pcie_ops dw_pcie_ops = {
>> + .start_link = stm32_pcie_start_link,
>> + .stop_link = stm32_pcie_stop_link,
>> +};
>> +
>> +static int stm32_pcie_enable_resources(struct stm32_pcie *stm32_pcie)
>> +{
>> + int ret;
>> +
>> + ret = phy_init(stm32_pcie->phy);
>> + if (ret)
>> + return ret;
>> +
>> + ret = clk_prepare_enable(stm32_pcie->clk);
>> + if (ret)
>> + phy_exit(stm32_pcie->phy);
>> +
>> + return ret;
>> +}
>> +
>> +static void stm32_pcie_disable_resources(struct stm32_pcie *stm32_pcie)
>> +{
>> + clk_disable_unprepare(stm32_pcie->clk);
>> +
>> + phy_exit(stm32_pcie->phy);
>> +}
>> +
>> +static void stm32_pcie_perst_assert(struct dw_pcie *pci)
>> +{
>> + struct stm32_pcie *stm32_pcie = to_stm32_pcie(pci);
>> + struct device *dev = pci->dev;
>> +
>> + dev_dbg(dev, "PERST asserted by host. Shutting down the PCIe link\n");
>> +
>> + /*
>> + * Do not try to release resources if the PERST# is
>> + * asserted before the link is started.
>
> Make use of 80 columns.
>
>> + */
>> + if (stm32_pcie->link_status == STM32_PCIE_EP_LINK_DISABLED) {
>> + dev_dbg(pci->dev, "Link is already disabled\n");
>> + return;
>> + }
>> +
>> + stm32_pcie_disable_link(pci);
>> +
>> + stm32_pcie_disable_resources(stm32_pcie);
>> +
>> + pm_runtime_put_sync(dev);
>> +
>> + stm32_pcie->link_status = STM32_PCIE_EP_LINK_DISABLED;
>> +}
>> +
>> +static void stm32_pcie_perst_deassert(struct dw_pcie *pci)
>> +{
>> + struct stm32_pcie *stm32_pcie = to_stm32_pcie(pci);
>> + struct device *dev = pci->dev;
>> + struct dw_pcie_ep *ep = &pci->ep;
>> + int ret;
>> +
>> + if (stm32_pcie->link_status == STM32_PCIE_EP_LINK_ENABLED) {
>> + dev_dbg(pci->dev, "Link is already enabled\n");
>> + return;
>> + }
>> +
>> + dev_dbg(dev, "PERST de-asserted by host. Starting link training\n");
>> +
>> + ret = pm_runtime_resume_and_get(dev);
>> + if (ret < 0) {
>> + dev_err(dev, "pm runtime resume failed: %d\n", ret);
>> + return;
>> + }
>> +
>> + ret = stm32_pcie_enable_resources(stm32_pcie);
>> + if (ret) {
>> + dev_err(dev, "Failed to enable resources: %d\n", ret);
>> + goto err_pm_put_sync;
>> + }
>> +
>> + ret = dw_pcie_ep_init_registers(ep);
>> + if (ret) {
>> + dev_err(dev, "Failed to complete initialization: %d\n", ret);
>> + goto err_disable_resources;
>> + }
>> +
>> + pci_epc_init_notify(ep->epc);
>> +
>> + ret = stm32_pcie_enable_link(pci);
>> + if (ret) {
>> + dev_err(dev, "PCIe Cannot establish link: %d\n", ret);
>> + goto err_deinit_notify;
>> + }
>
> Link is supposed to be enabled only by the start_link() callback.
OK. and then I need to remove the IRQ_NOAUTOEN for perst_irq, which make
the link_status unnecessary and results in simplifications. thank you
>
>> +
>> + stm32_pcie->link_status = STM32_PCIE_EP_LINK_ENABLED;
>> +
>> + return;
>> +
>> +err_deinit_notify:
>> + pci_epc_deinit_notify(ep->epc);
>> +
>> +err_disable_resources:
>> + stm32_pcie_disable_resources(stm32_pcie);
>> +
>> +err_pm_put_sync:
>> + pm_runtime_put_sync(dev);
>> +}
>> +
>> +static irqreturn_t stm32_pcie_ep_perst_irq_thread(int irq, void *data)
>> +{
>> + struct stm32_pcie *stm32_pcie = data;
>> + struct dw_pcie *pci = &stm32_pcie->pci;
>> + u32 perst;
>> +
>> + perst = gpiod_get_value(stm32_pcie->perst_gpio);
>> + if (perst)
>> + stm32_pcie_perst_assert(pci);
>> + else
>> + stm32_pcie_perst_deassert(pci);
>> +
>> + return IRQ_HANDLED;
>> +}
>> +
>> +static int stm32_add_pcie_ep(struct stm32_pcie *stm32_pcie,
>> + struct platform_device *pdev)
>> +{
>> + struct dw_pcie_ep *ep = &stm32_pcie->pci.ep;
>> + struct device *dev = &pdev->dev;
>> + int ret;
>> +
>> + ret = pm_runtime_resume_and_get(dev);
>> + if (ret < 0) {
>> + dev_err(dev, "pm runtime resume failed: %d\n", ret);
>> + return ret;
>> + }
>> +
>> + ret = regmap_update_bits(stm32_pcie->regmap, SYSCFG_PCIECR,
>> + STM32MP25_PCIECR_TYPE_MASK,
>> + STM32MP25_PCIECR_EP);
>> + if (ret) {
>> + goto err_pm_put_sync;
>> + return ret;
>> + }
>> +
>> + reset_control_assert(stm32_pcie->rst);
>> + reset_control_deassert(stm32_pcie->rst);
>> +
>> + ep->ops = &stm32_pcie_ep_ops;
>> +
>> + ret = dw_pcie_ep_init(ep);
>> + if (ret) {
>> + dev_err(dev, "failed to initialize ep: %d\n", ret);
>> + goto err_pm_put_sync;
>> + }
>> +
>> + ret = stm32_pcie_enable_resources(stm32_pcie);
>> + if (ret) {
>> + dev_err(dev, "failed to enable resources: %d\n", ret);
>> + goto err_ep_deinit;
>> + }
>> +
>> + ret = dw_pcie_ep_init_registers(ep);
>> + if (ret) {
>> + dev_err(dev, "Failed to initialize DWC endpoint registers\n");
>> + goto err_disable_resources;
>> + }
>> +
>> + pci_epc_init_notify(ep->epc);
>> +
>
> You are calling dw_pcie_ep_init_registers() and pci_epc_init_notify() from 2
> places. I think the one in stm32_pcie_perst_deassert() should be dropped since
> the DBI registers are available at this point itself.
The DBI registers need to be rewritten as a results of phy_init()
resetting the PCIe core on RCC phy_reset :
RCC phy_reset is connected to power_up_rst_n, causing the PCIe logic to
be reset when it should not be for a warm reset.
I will document this bug in this part of the code.
Christian
>
> - Mani
>
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