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[PATCH v3 2/6] PCI: imx6: Toggle the cold reset for i.MX95 PCIe

Richard Zhu posted 6 patches 8 months, 3 weeks ago
There is a newer version of this series
[PATCH v3 2/6] PCI: imx6: Toggle the cold reset for i.MX95 PCIe
Posted by Richard Zhu 8 months, 3 weeks ago 
Add the cold reset toggle for i.MX95 PCIe to align PHY's power up sequency.

Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
---
 drivers/pci/controller/dwc/pci-imx6.c | 42 +++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 57aa777231ae..6051b3b5928f 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -71,6 +71,9 @@
 #define IMX95_SID_MASK				GENMASK(5, 0)
 #define IMX95_MAX_LUT				32
 
+#define IMX95_PCIE_RST_CTRL			0x3010
+#define IMX95_PCIE_COLD_RST			BIT(0)
+
 #define to_imx_pcie(x)	dev_get_drvdata((x)->dev)
 
 enum imx_pcie_variants {
@@ -773,6 +776,43 @@ static int imx7d_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
 	return 0;
 }
 
+static int imx95_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
+{
+	u32 val;
+
+	if (assert) {
+		/*
+		 * From i.MX95 PCIe PHY perspective, the COLD reset toggle
+		 * should be complete after power-up by the following sequence.
+		 *                 > 10us(at power-up)
+		 *                 > 10ns(warm reset)
+		 *               |<------------>|
+		 *                ______________
+		 * phy_reset ____/              \________________
+		 *                                   ____________
+		 * ref_clk_en_______________________/
+		 * Toggle COLD reset aligned with this sequence for i.MX95 PCIe.
+		 */
+		regmap_set_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_RST_CTRL,
+				IMX95_PCIE_COLD_RST);
+		/*
+		 * To make sure delay enough time, do regmap_read_bypassed
+		 * before udelay(). Since udelay() might not use MMIO, and cause
+		 * delay time less than setting value.
+		 */
+		regmap_read_bypassed(imx_pcie->iomuxc_gpr, IMX95_PCIE_RST_CTRL,
+				     &val);
+		udelay(15);
+		regmap_clear_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_RST_CTRL,
+				  IMX95_PCIE_COLD_RST);
+		regmap_read_bypassed(imx_pcie->iomuxc_gpr, IMX95_PCIE_RST_CTRL,
+				     &val);
+		udelay(10);
+	}
+
+	return 0;
+}
+
 static void imx_pcie_assert_core_reset(struct imx_pcie *imx_pcie)
 {
 	reset_control_assert(imx_pcie->pciephy_reset);
@@ -1762,6 +1802,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
 		.ltssm_mask = IMX95_PCIE_LTSSM_EN,
 		.mode_off[0]  = IMX95_PE0_GEN_CTRL_1,
 		.mode_mask[0] = IMX95_PCIE_DEVICE_TYPE,
+		.core_reset = imx95_pcie_core_reset,
 		.init_phy = imx95_pcie_init_phy,
 	},
 	[IMX8MQ_EP] = {
@@ -1815,6 +1856,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
 		.mode_off[0]  = IMX95_PE0_GEN_CTRL_1,
 		.mode_mask[0] = IMX95_PCIE_DEVICE_TYPE,
 		.init_phy = imx95_pcie_init_phy,
+		.core_reset = imx95_pcie_core_reset,
 		.epc_features = &imx95_pcie_epc_features,
 		.mode = DW_PCIE_EP_TYPE,
 	},
-- 
2.37.1
Re: [PATCH v3 2/6] PCI: imx6: Toggle the cold reset for i.MX95 PCIe
Posted by Manivannan Sadhasivam 8 months, 2 weeks ago 
On Fri, Mar 28, 2025 at 11:02:09AM +0800, Richard Zhu wrote:
> Add the cold reset toggle for i.MX95 PCIe to align PHY's power up sequency.

What do you mean by 'cold' reset? Is it 'core' reset? I see both terminologies
used in the code.

> 
> Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 42 +++++++++++++++++++++++++++
>  1 file changed, 42 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 57aa777231ae..6051b3b5928f 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -71,6 +71,9 @@
>  #define IMX95_SID_MASK				GENMASK(5, 0)
>  #define IMX95_MAX_LUT				32
>  
> +#define IMX95_PCIE_RST_CTRL			0x3010
> +#define IMX95_PCIE_COLD_RST			BIT(0)
> +
>  #define to_imx_pcie(x)	dev_get_drvdata((x)->dev)
>  
>  enum imx_pcie_variants {
> @@ -773,6 +776,43 @@ static int imx7d_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
>  	return 0;
>  }
>  
> +static int imx95_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
> +{
> +	u32 val;
> +
> +	if (assert) {
> +		/*
> +		 * From i.MX95 PCIe PHY perspective, the COLD reset toggle
> +		 * should be complete after power-up by the following sequence.
> +		 *                 > 10us(at power-up)
> +		 *                 > 10ns(warm reset)
> +		 *               |<------------>|
> +		 *                ______________
> +		 * phy_reset ____/              \________________
> +		 *                                   ____________
> +		 * ref_clk_en_______________________/
> +		 * Toggle COLD reset aligned with this sequence for i.MX95 PCIe.
> +		 */
> +		regmap_set_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_RST_CTRL,
> +				IMX95_PCIE_COLD_RST);

Is this really COLD reset? Or CORE reset?

> +		/*
> +		 * To make sure delay enough time, do regmap_read_bypassed
> +		 * before udelay(). Since udelay() might not use MMIO, and cause
> +		 * delay time less than setting value.
> +		 */

This comment could be rephrased:

		/*
		 * Make sure the write to IMX95_PCIE_RST_CTRL is flushed to the
		 * hardware by doing a read. Otherwise, there is no guarantee
		 * that the write has reached the hardware before udelay().
		 */

- Mani

-- 
மணிவண்ணன் சதாசிவம்
Re: [PATCH v3 2/6] PCI: imx6: Toggle the cold reset for i.MX95 PCIe
Posted by Frank Li 8 months, 3 weeks ago 
On Fri, Mar 28, 2025 at 11:02:09AM +0800, Richard Zhu wrote:
> Add the cold reset toggle for i.MX95 PCIe to align PHY's power up sequency.
>
> Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>

Reviewed-by: Frank Li <Frank.Li@nxp.com>

> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 42 +++++++++++++++++++++++++++
>  1 file changed, 42 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 57aa777231ae..6051b3b5928f 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -71,6 +71,9 @@
>  #define IMX95_SID_MASK				GENMASK(5, 0)
>  #define IMX95_MAX_LUT				32
>
> +#define IMX95_PCIE_RST_CTRL			0x3010
> +#define IMX95_PCIE_COLD_RST			BIT(0)
> +
>  #define to_imx_pcie(x)	dev_get_drvdata((x)->dev)
>
>  enum imx_pcie_variants {
> @@ -773,6 +776,43 @@ static int imx7d_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
>  	return 0;
>  }
>
> +static int imx95_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
> +{
> +	u32 val;
> +
> +	if (assert) {
> +		/*
> +		 * From i.MX95 PCIe PHY perspective, the COLD reset toggle
> +		 * should be complete after power-up by the following sequence.
> +		 *                 > 10us(at power-up)
> +		 *                 > 10ns(warm reset)
> +		 *               |<------------>|
> +		 *                ______________
> +		 * phy_reset ____/              \________________
> +		 *                                   ____________
> +		 * ref_clk_en_______________________/
> +		 * Toggle COLD reset aligned with this sequence for i.MX95 PCIe.
> +		 */
> +		regmap_set_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_RST_CTRL,
> +				IMX95_PCIE_COLD_RST);
> +		/*
> +		 * To make sure delay enough time, do regmap_read_bypassed
> +		 * before udelay(). Since udelay() might not use MMIO, and cause
> +		 * delay time less than setting value.
> +		 */
> +		regmap_read_bypassed(imx_pcie->iomuxc_gpr, IMX95_PCIE_RST_CTRL,
> +				     &val);
> +		udelay(15);
> +		regmap_clear_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_RST_CTRL,
> +				  IMX95_PCIE_COLD_RST);
> +		regmap_read_bypassed(imx_pcie->iomuxc_gpr, IMX95_PCIE_RST_CTRL,
> +				     &val);
> +		udelay(10);
> +	}
> +
> +	return 0;
> +}
> +
>  static void imx_pcie_assert_core_reset(struct imx_pcie *imx_pcie)
>  {
>  	reset_control_assert(imx_pcie->pciephy_reset);
> @@ -1762,6 +1802,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  		.ltssm_mask = IMX95_PCIE_LTSSM_EN,
>  		.mode_off[0]  = IMX95_PE0_GEN_CTRL_1,
>  		.mode_mask[0] = IMX95_PCIE_DEVICE_TYPE,
> +		.core_reset = imx95_pcie_core_reset,
>  		.init_phy = imx95_pcie_init_phy,
>  	},
>  	[IMX8MQ_EP] = {
> @@ -1815,6 +1856,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  		.mode_off[0]  = IMX95_PE0_GEN_CTRL_1,
>  		.mode_mask[0] = IMX95_PCIE_DEVICE_TYPE,
>  		.init_phy = imx95_pcie_init_phy,
> +		.core_reset = imx95_pcie_core_reset,
>  		.epc_features = &imx95_pcie_epc_features,
>  		.mode = DW_PCIE_EP_TYPE,
>  	},
> --
> 2.37.1
>

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