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

[Manivannan Sadhasivam]

On Mon, May 12, 2025 at 06:06:16PM +0200, Christian Bruel wrote:
> 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 at 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.
> 

Yes!

> > 
> > > +	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."
> 

Since PERST# is level triggered, the endpoint should still receive the PERST#
deassert interrupt if the host was already booted. In that case, these will be
called by the stm32_pcie_perst_deassert() function.

- Mani

-- 
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