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Date: Sat, 27 Apr 2024 15:49:50 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
To: Frank Li <Frank.Li@nxp.com>
Cc: Richard Zhu <hongxing.zhu@nxp.com>,
	Lucas Stach <l.stach@pengutronix.de>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= <kw@linux.com>,
	Rob Herring <robh@kernel.org>, Bjorn Helgaas <bhelgaas@google.com>,
	Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>,
	NXP Linux Team <linux-imx@nxp.com>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Mark Brown <broonie@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>, linux-pci@vger.kernel.org,
	imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
	devicetree@vger.kernel.org
Subject: Re: [PATCH v3 07/11] PCI: imx: Simplify switch-case logic by involve
 core_reset callback
Message-ID: <20240427101950.GL1981@thinkpad>
References: <20240402-pci2_upstream-v3-0-803414bdb430@nxp.com>
 <20240402-pci2_upstream-v3-7-803414bdb430@nxp.com>
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In-Reply-To: <20240402-pci2_upstream-v3-7-803414bdb430@nxp.com>

On Tue, Apr 02, 2024 at 10:33:43AM -0400, Frank Li wrote:
> Instead of using the switch case statement to assert/dassert the core reset
> handled by this driver itself, let's introduce a new callback core_reset()
> and define it for platforms that require it. This simplifies the code.
> 
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
>  drivers/pci/controller/dwc/pcie-imx.c | 131 ++++++++++++++++++----------------
>  1 file changed, 68 insertions(+), 63 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-imx.c b/drivers/pci/controller/dwc/pcie-imx.c
> index 77dae5c3f7057..af0f960f28757 100644
> --- a/drivers/pci/controller/dwc/pcie-imx.c
> +++ b/drivers/pci/controller/dwc/pcie-imx.c
> @@ -104,6 +104,7 @@ struct imx_pcie_drvdata {
>  	const struct pci_epc_features *epc_features;
>  	int (*init_phy)(struct imx_pcie *pcie);
>  	int (*set_ref_clk)(struct imx_pcie *pcie, bool enable);
> +	int (*core_reset)(struct imx_pcie *pcie, bool assert);
>  };
>  
>  struct imx_pcie {
> @@ -671,35 +672,72 @@ static void imx_pcie_clk_disable(struct imx_pcie *imx_pcie)
>  	clk_bulk_disable_unprepare(imx_pcie->drvdata->clks_cnt, imx_pcie->clks);
>  }
>  
> +static int imx6sx_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
> +{
> +	regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR12, IMX6SX_GPR12_PCIE_TEST_POWERDOWN,
> +			   assert ? IMX6SX_GPR12_PCIE_TEST_POWERDOWN : 0);

Earlier, this register was not cleared during deassert. Is if fine?

> +	/* Force PCIe PHY reset */
> +	regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR5, IMX6SX_GPR5_PCIE_BTNRST_RESET,
> +			   assert ? IMX6SX_GPR5_PCIE_BTNRST_RESET : 0);
> +	return 0;
> +}
> +
> +static int imx6qp_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
> +{
> +	regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_SW_RST,
> +			   assert ? IMX6Q_GPR1_PCIE_SW_RST : 0);
> +	if (!assert)
> +		usleep_range(200, 500);
> +
> +	return 0;
> +}
> +
> +static int imx6q_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
> +{
> +	regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_TEST_PD,
> +			   assert ? IMX6Q_GPR1_PCIE_TEST_PD : 0);
> +
> +	regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1, IMX6Q_GPR1_PCIE_REF_CLK_EN,
> +			   assert ? 0 : IMX6Q_GPR1_PCIE_REF_CLK_EN);
> +

Same comment as above.

> +	return 0;
> +}
> +
> +static int imx7d_pcie_core_reset(struct imx_pcie *imx_pcie, bool assert)
> +{
> +	struct dw_pcie *pci = imx_pcie->pci;
> +	struct device *dev = pci->dev;
> +
> +	if (assert)
> +		return 0;
> +
> +	/*
> +	 * Workaround for ERR010728, failure of PCI-e PLL VCO to oscillate, especially when cold.

What does 'especially when cold' means? I know it is an old comment, but still
it is not very clear.

> +	 * This turns off "Duty-cycle Corrector" and other mysterious undocumented things.

Same comment as previous patch.

> +	 */
> +
> +	if (likely(imx_pcie->phy_base)) {
> +		/* De-assert DCC_FB_EN */
> +		writel(PCIE_PHY_CMN_REG4_DCC_FB_EN, imx_pcie->phy_base + PCIE_PHY_CMN_REG4);
> +		/* Assert RX_EQS and RX_EQS_SEL */
> +		writel(PCIE_PHY_CMN_REG24_RX_EQ_SEL | PCIE_PHY_CMN_REG24_RX_EQ,
> +		       imx_pcie->phy_base + PCIE_PHY_CMN_REG24);
> +		/* Assert ATT_MODE */
> +		writel(PCIE_PHY_CMN_REG26_ATT_MODE, imx_pcie->phy_base + PCIE_PHY_CMN_REG26);

Why does this workaround a part of core_reset handling? This function doesn't
look like performing reset at all.

- Mani

> +	} else {
> +		dev_warn(dev, "Unable to apply ERR010728 workaround. DT missing fsl,imx7d-pcie-phy phandle ?\n");
> +	}
> +	imx7d_pcie_wait_for_phy_pll_lock(imx_pcie);
> +	return 0;
> +}
> +
>  static void imx_pcie_assert_core_reset(struct imx_pcie *imx_pcie)
>  {
>  	reset_control_assert(imx_pcie->pciephy_reset);
>  	reset_control_assert(imx_pcie->apps_reset);
>  
> -	switch (imx_pcie->drvdata->variant) {
> -	case IMX6SX:
> -		regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR12,
> -				   IMX6SX_GPR12_PCIE_TEST_POWERDOWN,
> -				   IMX6SX_GPR12_PCIE_TEST_POWERDOWN);
> -		/* Force PCIe PHY reset */
> -		regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR5,
> -				   IMX6SX_GPR5_PCIE_BTNRST_RESET,
> -				   IMX6SX_GPR5_PCIE_BTNRST_RESET);
> -		break;
> -	case IMX6QP:
> -		regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1,
> -				   IMX6Q_GPR1_PCIE_SW_RST,
> -				   IMX6Q_GPR1_PCIE_SW_RST);
> -		break;
> -	case IMX6Q:
> -		regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1,
> -				   IMX6Q_GPR1_PCIE_TEST_PD, 1 << 18);
> -		regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1,
> -				   IMX6Q_GPR1_PCIE_REF_CLK_EN, 0 << 16);
> -		break;
> -	default:
> -		break;
> -	}
> +	if (imx_pcie->drvdata->core_reset)
> +		imx_pcie->drvdata->core_reset(imx_pcie, true);
>  
>  	/* Some boards don't have PCIe reset GPIO. */
>  	if (gpio_is_valid(imx_pcie->reset_gpio))
> @@ -709,47 +747,10 @@ static void imx_pcie_assert_core_reset(struct imx_pcie *imx_pcie)
>  
>  static int imx_pcie_deassert_core_reset(struct imx_pcie *imx_pcie)
>  {
> -	struct dw_pcie *pci = imx_pcie->pci;
> -	struct device *dev = pci->dev;
> -
>  	reset_control_deassert(imx_pcie->pciephy_reset);
>  
> -	switch (imx_pcie->drvdata->variant) {
> -	case IMX7D:
> -		/* Workaround for ERR010728, failure of PCI-e PLL VCO to
> -		 * oscillate, especially when cold.  This turns off "Duty-cycle
> -		 * Corrector" and other mysterious undocumented things.
> -		 */
> -		if (likely(imx_pcie->phy_base)) {
> -			/* De-assert DCC_FB_EN */
> -			writel(PCIE_PHY_CMN_REG4_DCC_FB_EN,
> -			       imx_pcie->phy_base + PCIE_PHY_CMN_REG4);
> -			/* Assert RX_EQS and RX_EQS_SEL */
> -			writel(PCIE_PHY_CMN_REG24_RX_EQ_SEL
> -				| PCIE_PHY_CMN_REG24_RX_EQ,
> -			       imx_pcie->phy_base + PCIE_PHY_CMN_REG24);
> -			/* Assert ATT_MODE */
> -			writel(PCIE_PHY_CMN_REG26_ATT_MODE,
> -			       imx_pcie->phy_base + PCIE_PHY_CMN_REG26);
> -		} else {
> -			dev_warn(dev, "Unable to apply ERR010728 workaround. DT missing fsl,imx7d-pcie-phy phandle ?\n");
> -		}
> -
> -		imx7d_pcie_wait_for_phy_pll_lock(imx_pcie);
> -		break;
> -	case IMX6SX:
> -		regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR5,
> -				   IMX6SX_GPR5_PCIE_BTNRST_RESET, 0);
> -		break;
> -	case IMX6QP:
> -		regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR1,
> -				   IMX6Q_GPR1_PCIE_SW_RST, 0);
> -
> -		usleep_range(200, 500);
> -		break;
> -	default:
> -		break;
> -	}
> +	if (imx_pcie->drvdata->core_reset)
> +		imx_pcie->drvdata->core_reset(imx_pcie, false);
>  
>  	/* Some boards don't have PCIe reset GPIO. */
>  	if (gpio_is_valid(imx_pcie->reset_gpio)) {
> @@ -1447,6 +1448,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  		.mode_mask[0] = IMX6Q_GPR12_DEVICE_TYPE,
>  		.init_phy = imx_pcie_init_phy,
>  		.set_ref_clk = imx6q_pcie_set_ref_clk,
> +		.core_reset = imx6q_pcie_core_reset,
>  	},
>  	[IMX6SX] = {
>  		.variant = IMX6SX,
> @@ -1462,6 +1464,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  		.mode_mask[0] = IMX6Q_GPR12_DEVICE_TYPE,
>  		.init_phy = imx6sx_pcie_init_phy,
>  		.set_ref_clk = imx6sx_pcie_set_ref_clk,
> +		.core_reset = imx6sx_pcie_core_reset,
>  	},
>  	[IMX6QP] = {
>  		.variant = IMX6QP,
> @@ -1478,6 +1481,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  		.mode_mask[0] = IMX6Q_GPR12_DEVICE_TYPE,
>  		.init_phy = imx_pcie_init_phy,
>  		.set_ref_clk = imx6q_pcie_set_ref_clk,
> +		.core_reset = imx6qp_pcie_core_reset,
>  	},
>  	[IMX7D] = {
>  		.variant = IMX7D,
> @@ -1491,6 +1495,7 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  		.mode_mask[0] = IMX6Q_GPR12_DEVICE_TYPE,
>  		.init_phy = imx7d_pcie_init_phy,
>  		.set_ref_clk = imx7d_pcie_set_ref_clk,
> +		.core_reset = imx7d_pcie_core_reset,
>  	},
>  	[IMX8MQ] = {
>  		.variant = IMX8MQ,
> 
> -- 
> 2.34.1
> 

-- 
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