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

[Hans Zhang <hans.zhang@cixtech.com>]

On 10/21/2025 3:48 PM, Shawn Lin wrote:
> EXTERNAL EMAIL
> 
> The driver should set app_clk_req_n(clkreq ready) of PCIE_CLIENT_POWER reg
> to support L1sub. Otherwise, unset app_clk_req_n and pull down CLKREQ#.
> 
> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
> ---
>   drivers/pci/controller/dwc/pcie-dw-rockchip.c | 31 ++++++++++++++-----
>   1 file changed, 23 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> index 87dd2dd188b4..8a52ff73ec46 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              0x2c
> +#define  PCIE_CLKREQ_READY             0x10001
> +#define  PCIE_CLKREQ_NOT_READY         0x10000
> +#define  PCIE_CLKREQ_PULL_DOWN         0x30001000
> +
>   /* Hot Reset Control Register */
>   #define PCIE_CLIENT_HOT_RESET_CTRL     0x180
>   #define  PCIE_LTSSM_APP_DLY2_EN                BIT(1)
> @@ -84,6 +90,7 @@ struct rockchip_pcie {
>          struct gpio_desc *rst_gpio;
>          struct irq_domain *irq_domain;
>          const struct rockchip_pcie_of_data *data;
> +       bool supports_clkreq;
>   };
> 
>   struct rockchip_pcie_of_data {
> @@ -199,15 +206,21 @@ 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, not a single rockchip platform
> - * performs these steps, so disable L1 substates until there is proper support.
> - */
> -static void rockchip_pcie_disable_l1sub(struct dw_pcie *pci)

Hi,

https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/commit/?h=controller/dw-rockchip&id=40331c63e7901a2cc75ce6b5d24d50601efb833d

Mani has already placed this part in the above branch. Can it be removed?

Best regards,
Hans


> +static void rockchip_pcie_enable_l1sub(struct dw_pcie *pci)
>   {
> +       struct rockchip_pcie *rockchip = to_rockchip_pcie(pci);
>          u32 cap, l1subcap;
> 
> +       /* Enable L1 substates if CLKREQ# is properly connected */
> +       if (rockchip->supports_clkreq) {
> +               /* Ready to have reference clock removed */
> +               rockchip_pcie_writel_apb(rockchip, PCIE_CLKREQ_READY, PCIE_CLIENT_POWER);
> +               return;
> +       }
> +
> +       /* Otherwise, pull down CLKREQ# and disable L1 substates */
> +       rockchip_pcie_writel_apb(rockchip, PCIE_CLKREQ_PULL_DOWN | PCIE_CLKREQ_NOT_READY,
> +                                PCIE_CLIENT_POWER);
>          cap = dw_pcie_find_ext_capability(pci, PCI_EXT_CAP_ID_L1SS);
>          if (cap) {
>                  l1subcap = dw_pcie_readl_dbi(pci, cap + PCI_L1SS_CAP);
> @@ -282,7 +295,7 @@ 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_disable_l1sub(pci);
> +       rockchip_pcie_enable_l1sub(pci);
>          rockchip_pcie_enable_l0s(pci);
> 
>          return 0;
> @@ -320,7 +333,7 @@ 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_disable_l1sub(pci);
> +       rockchip_pcie_enable_l1sub(pci);
>          rockchip_pcie_enable_l0s(pci);
>          rockchip_pcie_ep_hide_broken_ats_cap_rk3588(ep);
> 
> @@ -432,6 +445,8 @@ 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_pci_clkreq_present(pdev->dev.of_node);
> +
>          return 0;
>   }
> 
> --
> 2.43.0
> 
> 


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