[PATCH] PCI: dw-rockchip: Delay link training after hot reset in EP mode

[PATCH] PCI: dw-rockchip: Delay link training after hot reset in EP mode

[Niklas Cassel]

From: Wilfred Mallawa <wilfred.mallawa@wdc.com>

RK3588 TRM, section "11.6.1.3.3 Hot Reset and Link-Down Reset" states that:
"""
If you want to delay link re-establishment (after reset) so that you can
reprogram some registers through DBI, you must set app_ltssm_enable =0
immediately after core_rst_n as shown in above. This can be achieved by
enable the app_dly2_en, and end-up the delay by assert app_dly2_done.
"""

I.e. setting app_dly2_en will automatically deassert app_ltssm_enable on
a hot reset, and setting app_dly2_done will re-assert app_ltssm_enable,
re-enabling link training.

When receiving a hot reset/link-down IRQ when running in EP mode, we will
call dw_pcie_ep_linkdown(), which will call the .link_down() callback in
the currently bound endpoint function (EPF) drivers.

The callback in an EPF driver can theoretically take a long time to
complete, so make sure that the link is not re-established until after
dw_pcie_ep_linkdown() (which calls the .link_down() callback(s)
synchronously).

Signed-off-by: Wilfred Mallawa <wilfred.mallawa@wdc.com>
Co-developed-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 drivers/pci/controller/dwc/pcie-dw-rockchip.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
index c4bd7e0abdf0..05b8e4cbd30b 100644
--- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
+++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
@@ -61,6 +61,8 @@
 
 /* Hot Reset Control Register */
 #define PCIE_CLIENT_HOT_RESET_CTRL	0x180
+#define  PCIE_LTSSM_APP_DLY2_EN		BIT(1)
+#define  PCIE_LTSSM_APP_DLY2_DONE	BIT(3)
 #define  PCIE_LTSSM_ENABLE_ENHANCE	BIT(4)
 
 /* LTSSM Status Register */
@@ -487,7 +489,7 @@ static irqreturn_t rockchip_pcie_ep_sys_irq_thread(int irq, void *arg)
 	struct rockchip_pcie *rockchip = arg;
 	struct dw_pcie *pci = &rockchip->pci;
 	struct device *dev = pci->dev;
-	u32 reg;
+	u32 reg, val;
 
 	reg = rockchip_pcie_readl_apb(rockchip, PCIE_CLIENT_INTR_STATUS_MISC);
 	rockchip_pcie_writel_apb(rockchip, reg, PCIE_CLIENT_INTR_STATUS_MISC);
@@ -498,6 +500,10 @@ static irqreturn_t rockchip_pcie_ep_sys_irq_thread(int irq, void *arg)
 	if (reg & PCIE_LINK_REQ_RST_NOT_INT) {
 		dev_dbg(dev, "hot reset or link-down reset\n");
 		dw_pcie_ep_linkdown(&pci->ep);
+		/* Stop delaying link training. */
+		val = HIWORD_UPDATE_BIT(PCIE_LTSSM_APP_DLY2_DONE);
+		rockchip_pcie_writel_apb(rockchip, val,
+					 PCIE_CLIENT_HOT_RESET_CTRL);
 	}
 
 	if (reg & PCIE_RDLH_LINK_UP_CHGED) {
@@ -585,8 +591,11 @@ static int rockchip_pcie_configure_ep(struct platform_device *pdev,
 		return ret;
 	}
 
-	/* LTSSM enable control mode */
-	val = HIWORD_UPDATE_BIT(PCIE_LTSSM_ENABLE_ENHANCE);
+	/*
+	 * LTSSM enable control mode, and automatically delay link training on
+	 * hot reset/link-down reset.
+	 */
+	val = HIWORD_UPDATE_BIT(PCIE_LTSSM_ENABLE_ENHANCE | PCIE_LTSSM_APP_DLY2_EN);
 	rockchip_pcie_writel_apb(rockchip, val, PCIE_CLIENT_HOT_RESET_CTRL);
 
 	/*
-- 
2.49.0

Re: [PATCH] PCI: dw-rockchip: Delay link training after hot reset in EP mode

[Wilfred Mallawa]

On Thu, 2025-05-22 at 14:39 +0200, Niklas Cassel wrote:
> 
[snip]
>  	/*
Gentle ping :)

Re: [PATCH] PCI: dw-rockchip: Delay link training after hot reset in EP mode

[manivannan.sadhasivam]

On Thu, May 29, 2025 at 08:22:51AM +0000, Wilfred Mallawa wrote:
> On Thu, 2025-05-22 at 14:39 +0200, Niklas Cassel wrote:
> > 
> [snip]
> >  	/*
> Gentle ping :)
> 

Please give atleast 2 weeks of time before pinging the maintainers. Also,
the merge window is now open, so there won't be much activity until -rc1 is out.

- Mani

-- 
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Re: [PATCH] PCI: dw-rockchip: Delay link training after hot reset in EP mode

[Wilfred Mallawa]

On Thu, 2025-05-29 at 14:00 +0530, manivannan.sadhasivam@linaro.org
wrote:
> On Thu, May 29, 2025 at 08:22:51AM +0000, Wilfred Mallawa wrote:
> > On Thu, 2025-05-22 at 14:39 +0200, Niklas Cassel wrote:
> > > 
> > [snip]
> > >  	/*
> > Gentle ping :)
> > 
> 
> Please give atleast 2 weeks of time before pinging the maintainers.
> Also,
> the merge window is now open, so there won't be much activity until -
> rc1 is out.
> 
Understood, thanks for letting me know!

Wilfred
> - Mani

Re: [PATCH] PCI: dw-rockchip: Delay link training after hot reset in EP mode

[Manivannan Sadhasivam]

On Thu, May 22, 2025 at 02:39:59PM +0200, Niklas Cassel wrote:
> From: Wilfred Mallawa <wilfred.mallawa@wdc.com>
> 
> RK3588 TRM, section "11.6.1.3.3 Hot Reset and Link-Down Reset" states that:
> """
> If you want to delay link re-establishment (after reset) so that you can
> reprogram some registers through DBI, you must set app_ltssm_enable =0
> immediately after core_rst_n as shown in above. This can be achieved by
> enable the app_dly2_en, and end-up the delay by assert app_dly2_done.
> """
> 
> I.e. setting app_dly2_en will automatically deassert app_ltssm_enable on
> a hot reset, and setting app_dly2_done will re-assert app_ltssm_enable,
> re-enabling link training.
> 
> When receiving a hot reset/link-down IRQ when running in EP mode, we will
> call dw_pcie_ep_linkdown(), which will call the .link_down() callback in
> the currently bound endpoint function (EPF) drivers.
> 
> The callback in an EPF driver can theoretically take a long time to
> complete, so make sure that the link is not re-established until after
> dw_pcie_ep_linkdown() (which calls the .link_down() callback(s)
> synchronously).
> 
> Signed-off-by: Wilfred Mallawa <wilfred.mallawa@wdc.com>
> Co-developed-by: Niklas Cassel <cassel@kernel.org>
> Signed-off-by: Niklas Cassel <cassel@kernel.org>

This patch is not applying on top of v6.16-rc1. Please post it after rebasing.

- Mani

> ---
>  drivers/pci/controller/dwc/pcie-dw-rockchip.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> index c4bd7e0abdf0..05b8e4cbd30b 100644
> --- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> +++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
> @@ -61,6 +61,8 @@
>  
>  /* Hot Reset Control Register */
>  #define PCIE_CLIENT_HOT_RESET_CTRL	0x180
> +#define  PCIE_LTSSM_APP_DLY2_EN		BIT(1)
> +#define  PCIE_LTSSM_APP_DLY2_DONE	BIT(3)
>  #define  PCIE_LTSSM_ENABLE_ENHANCE	BIT(4)
>  
>  /* LTSSM Status Register */
> @@ -487,7 +489,7 @@ static irqreturn_t rockchip_pcie_ep_sys_irq_thread(int irq, void *arg)
>  	struct rockchip_pcie *rockchip = arg;
>  	struct dw_pcie *pci = &rockchip->pci;
>  	struct device *dev = pci->dev;
> -	u32 reg;
> +	u32 reg, val;
>  
>  	reg = rockchip_pcie_readl_apb(rockchip, PCIE_CLIENT_INTR_STATUS_MISC);
>  	rockchip_pcie_writel_apb(rockchip, reg, PCIE_CLIENT_INTR_STATUS_MISC);
> @@ -498,6 +500,10 @@ static irqreturn_t rockchip_pcie_ep_sys_irq_thread(int irq, void *arg)
>  	if (reg & PCIE_LINK_REQ_RST_NOT_INT) {
>  		dev_dbg(dev, "hot reset or link-down reset\n");
>  		dw_pcie_ep_linkdown(&pci->ep);
> +		/* Stop delaying link training. */
> +		val = HIWORD_UPDATE_BIT(PCIE_LTSSM_APP_DLY2_DONE);
> +		rockchip_pcie_writel_apb(rockchip, val,
> +					 PCIE_CLIENT_HOT_RESET_CTRL);
>  	}
>  
>  	if (reg & PCIE_RDLH_LINK_UP_CHGED) {
> @@ -585,8 +591,11 @@ static int rockchip_pcie_configure_ep(struct platform_device *pdev,
>  		return ret;
>  	}
>  
> -	/* LTSSM enable control mode */
> -	val = HIWORD_UPDATE_BIT(PCIE_LTSSM_ENABLE_ENHANCE);
> +	/*
> +	 * LTSSM enable control mode, and automatically delay link training on
> +	 * hot reset/link-down reset.
> +	 */
> +	val = HIWORD_UPDATE_BIT(PCIE_LTSSM_ENABLE_ENHANCE | PCIE_LTSSM_APP_DLY2_EN);
>  	rockchip_pcie_writel_apb(rockchip, val, PCIE_CLIENT_HOT_RESET_CTRL);
>  
>  	/*
> -- 
> 2.49.0
> 

-- 
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