Re: [PATCH v8 4/9] PCI: stm32: Add PCIe Endpoint support for STM32MP25

[Christian Bruel <christian.bruel@foss.st.com>]

Hello Manivannan,

On 4/30/25 09:50, Manivannan Sadhasivam wrote:
> On Wed, Apr 23, 2025 at 11:01:14AM +0200, 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@foss.st.com>
>> ---
>>   drivers/pci/controller/dwc/Kconfig         |  12 +
>>   drivers/pci/controller/dwc/Makefile        |   1 +
>>   drivers/pci/controller/dwc/pcie-stm32-ep.c | 414 +++++++++++++++++++++
>>   drivers/pci/controller/dwc/pcie-stm32.h    |   1 +
>>   4 files changed, 428 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 2aec5d2f9a46..aceff7d1ef33 100644
>> --- a/drivers/pci/controller/dwc/Kconfig
>> +++ b/drivers/pci/controller/dwc/Kconfig
>> @@ -422,6 +422,18 @@ config PCIE_STM32_HOST
>>   	  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.
> 
> Can you please use similar description for the RC driver also?
> 
> "Enables Root Complex (RC) support for the DesignWare core based PCIe host
> controller found in STM32MP25 SoC."

Yes, will align the messages

>> +
>> +	  This driver can also be built as a module. If so, the module
>> +	  will be called pcie-stm32-ep.
>> +
>>   config PCI_DRA7XX
>>   	tristate
>>   
> 
> [...]
> 
>> +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);
> 
> This needs to be called before devm_pm_runtime_enable().

OK. Also and we must use pm_runtime_get_noresume() here.

> 
>> +	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);
>> +
> 
> Hmm, looks like you need to duplicate dw_pcie_ep_init_registers() and
> pci_epc_init_notify() in stm32_pcie_perst_deassert() for hw specific reasons.
> So can you drop these from there?

We cannot remove dw_pcie_ep_init_registers() and 
dw_pcie_ep_init_registers() here because the PCIe registers need to be 
ready at the end of pcie_stm32_probe, as the host might already be 
running. In that case the host enumerates with /sys/bus/pci/rescan 
rather than asserting/deasserting PERST#.
Therefore, we do not need to reboot the host after initializing the EP."


> 
>> +	return 0;
>> +
>> +err_disable_resources:
>> +	stm32_pcie_disable_resources(stm32_pcie);
>> +
>> +err_ep_deinit:
>> +	dw_pcie_ep_deinit(ep);
>> +
>> +err_pm_put_sync:
>> +	pm_runtime_put_sync(dev);
>> +	return ret;
>> +}
>> +
>> +static int stm32_pcie_probe(struct platform_device *pdev)
>> +{
>> +	struct stm32_pcie *stm32_pcie;
>> +	struct device *dev = &pdev->dev;
>> +	int ret;
>> +
>> +	stm32_pcie = devm_kzalloc(dev, sizeof(*stm32_pcie), GFP_KERNEL);
>> +	if (!stm32_pcie)
>> +		return -ENOMEM;
>> +
>> +	stm32_pcie->pci.dev = dev;
>> +	stm32_pcie->pci.ops = &dw_pcie_ops;
>> +
>> +	stm32_pcie->regmap = syscon_regmap_lookup_by_compatible("st,stm32mp25-syscfg");
>> +	if (IS_ERR(stm32_pcie->regmap))
>> +		return dev_err_probe(dev, PTR_ERR(stm32_pcie->regmap),
>> +				     "No syscfg specified\n");
>> +
>> +	stm32_pcie->phy = devm_phy_get(dev, NULL);
>> +	if (IS_ERR(stm32_pcie->phy))
>> +		return dev_err_probe(dev, PTR_ERR(stm32_pcie->phy),
>> +				     "failed to get pcie-phy\n");
>> +
>> +	stm32_pcie->clk = devm_clk_get(dev, NULL);
>> +	if (IS_ERR(stm32_pcie->clk))
>> +		return dev_err_probe(dev, PTR_ERR(stm32_pcie->clk),
>> +				     "Failed to get PCIe clock source\n");
>> +
>> +	stm32_pcie->rst = devm_reset_control_get_exclusive(dev, NULL);
>> +	if (IS_ERR(stm32_pcie->rst))
>> +		return dev_err_probe(dev, PTR_ERR(stm32_pcie->rst),
>> +				     "Failed to get PCIe reset\n");
>> +
>> +	stm32_pcie->perst_gpio = devm_gpiod_get(dev, "reset", GPIOD_IN);
>> +	if (IS_ERR(stm32_pcie->perst_gpio))
>> +		return dev_err_probe(dev, PTR_ERR(stm32_pcie->perst_gpio),
>> +				     "Failed to get reset GPIO\n");
>> +
>> +	ret = phy_set_mode(stm32_pcie->phy, PHY_MODE_PCIE);
>> +	if (ret)
>> +		return ret;
>> +
>> +	platform_set_drvdata(pdev, stm32_pcie);
>> +
>> +	ret = devm_pm_runtime_enable(dev);
>> +	if (ret < 0) {
>> +		dev_err(dev, "Failed to enable pm runtime %d\n", ret);
> 
> Use dev_err_probe() please for consistency.

OK

thank you

Christian
> 
> - Mani
>