Re: [PATCH 3/4] PCI: dw-rockchip: Configure L1sub support

["Diederik de Haas" <diederik@cknow-tech.com>]

On Tue Nov 11, 2025 at 11:16 PM CET, Bjorn Helgaas wrote:
> From: Shawn Lin <shawn.lin@rock-chips.com>
>
> L1 PM Substates for RC mode require support in the dw-rockchip driver
> including proper handling of the CLKREQ# sideband signal. It is mostly
> handled by hardware, but software still needs to set the clkreq fields
> in the PCIE_CLIENT_POWER_CON register to match the hardware implementation.
>
> For more details, see section '18.6.6.4 L1 Substate' in the RK3658 TRM 1.1

s/RK3658/RK3568/

Sorry,
  Diederik

> Part 2, or section '11.6.6.4 L1 Substate' in the RK3588 TRM 1.0 Part2.
>
> Meanwhile, for the EP mode, we haven't prepared enough to actually support
> L1 PM Substates yet. So disable it now until proper support is added later.
>
> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
> [bhelgaas: set pci->l1ss_support so DWC core preserves L1SS Capability bits;
> drop corresponding code here]
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> Link: https://patch.msgid.link/1761187883-150120-1-git-send-email-shawn.lin@rock-chips.com
> ---
>  drivers/pci/controller/dwc/pcie-dw-rockchip.c | 38 +++++++++++++++++++
>  1 file changed, 38 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> index 3e2752c7dd09..62a095752833 100644
> --- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> +++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> @@ -62,6 +62,12 @@
>  /* Interrupt Mask Register Related to Miscellaneous Operation */
>  #define PCIE_CLIENT_INTR_MASK_MISC	0x24
>  
> +/* Power Management Control Register */
> +#define PCIE_CLIENT_POWER_CON		0x2c
> +#define  PCIE_CLKREQ_READY		FIELD_PREP_WM16(BIT(0), 1)
> +#define  PCIE_CLKREQ_NOT_READY		FIELD_PREP_WM16(BIT(0), 0)
> +#define  PCIE_CLKREQ_PULL_DOWN		FIELD_PREP_WM16(GENMASK(13, 12), 1)
> +
>  /* Hot Reset Control Register */
>  #define PCIE_CLIENT_HOT_RESET_CTRL	0x180
>  #define  PCIE_LTSSM_APP_DLY2_EN		BIT(1)
> @@ -85,6 +91,7 @@ struct rockchip_pcie {
>  	struct regulator *vpcie3v3;
>  	struct irq_domain *irq_domain;
>  	const struct rockchip_pcie_of_data *data;
> +	bool supports_clkreq;
>  };
>  
>  struct rockchip_pcie_of_data {
> @@ -200,6 +207,32 @@ static bool rockchip_pcie_link_up(struct dw_pcie *pci)
>  	return FIELD_GET(PCIE_LINKUP_MASK, val) == PCIE_LINKUP;
>  }
>  
> +/*
> + * See e.g. section '11.6.6.4 L1 Substate' in the RK3588 TRM V1.0 for the steps
> + * needed to support L1 substates. Currently, just enable L1 substates for RC
> + * mode if CLKREQ# is properly connected and supports-clkreq is present in DT.
> + * For EP mode, there are more things should be done to actually save power in
> + * L1 substates, so disable L1 substates until there is proper support.
> + */
> +static void rockchip_pcie_configure_l1sub(struct dw_pcie *pci)
> +{
> +	struct rockchip_pcie *rockchip = to_rockchip_pcie(pci);
> +
> +	/* Enable L1 substates if CLKREQ# is properly connected */
> +	if (rockchip->supports_clkreq &&
> +	    rockchip->data->mode == DW_PCIE_RC_TYPE ) {
> +		rockchip_pcie_writel_apb(rockchip, PCIE_CLKREQ_READY,
> +					 PCIE_CLIENT_POWER_CON);
> +		pci->l1ss_support = true;
> +		return;
> +	}
> +
> +	/* Otherwise, pull down CLKREQ# */
> +	rockchip_pcie_writel_apb(rockchip,
> +				 PCIE_CLKREQ_PULL_DOWN | PCIE_CLKREQ_NOT_READY,
> +				 PCIE_CLIENT_POWER_CON);
> +}
> +
>  static void rockchip_pcie_enable_l0s(struct dw_pcie *pci)
>  {
>  	u32 cap, lnkcap;
> @@ -264,6 +297,7 @@ static int rockchip_pcie_host_init(struct dw_pcie_rp *pp)
>  	irq_set_chained_handler_and_data(irq, rockchip_pcie_intx_handler,
>  					 rockchip);
>  
> +	rockchip_pcie_configure_l1sub(pci);
>  	rockchip_pcie_enable_l0s(pci);
>  
>  	return 0;
> @@ -301,6 +335,7 @@ static void rockchip_pcie_ep_init(struct dw_pcie_ep *ep)
>  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
>  	enum pci_barno bar;
>  
> +	rockchip_pcie_configure_l1sub(pci);
>  	rockchip_pcie_enable_l0s(pci);
>  	rockchip_pcie_ep_hide_broken_ats_cap_rk3588(ep);
>  
> @@ -412,6 +447,9 @@ static int rockchip_pcie_resource_get(struct platform_device *pdev,
>  		return dev_err_probe(&pdev->dev, PTR_ERR(rockchip->rst),
>  				     "failed to get reset lines\n");
>  
> +	rockchip->supports_clkreq = of_property_read_bool(pdev->dev.of_node,
> +							  "supports-clkreq");
> +
>  	return 0;
>  }
>