linux-kernel - Re: [PATCH v7 06/10] PCI: imx6: Fix the missing reference clock disable logic

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Message-ID: <20250116170114.GA561930@bhelgaas>
Date: Thu, 16 Jan 2025 11:01:14 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Richard Zhu <hongxing.zhu@....com>
Cc: l.stach@...gutronix.de, bhelgaas@...gle.com, lpieralisi@...nel.org,
	kw@...ux.com, manivannan.sadhasivam@...aro.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, shawnguo@...nel.org,
	frank.li@....com, s.hauer@...gutronix.de, festevam@...il.com,
	imx@...ts.linux.dev, kernel@...gutronix.de,
	linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 06/10] PCI: imx6: Fix the missing reference clock
 disable logic

On Tue, Nov 26, 2024 at 03:56:58PM +0800, Richard Zhu wrote:
> Ensure the *_enable_ref_clk() function is symmetric by addressing missing
> disable parts on some platforms.
> 
> Fixes: d0a75c791f98 ("PCI: imx6: Factor out ref clock disable to match enable")

The patch below looks fine to me, and I guess it's more than just
making the code prettier; it also actually *fixes* something, right?

It looks like a functional change because imx_pcie_clk_enable() will
now enable the IMX7D refclk when it didn't before, and
imx_pcie_clk_disable() will disable the IMX6SX and IMX8M* refclk when
it didn't before?

But I don't think the Fixes: tag is correct.  I looked at uses of
these symbols:

  IMX6SX_GPR12_PCIE_TEST_POWERDOWN
    enabled by imx6_pcie_enable_ref_clk()
    disabled by imx6_pcie_assert_core_reset()

  IMX7D_GPR12_PCIE_PHY_REFCLK_SEL
    enabled by imx6_pcie_init_phy()
    disabled by imx6_pcie_clk_disable()

  IMX8MQ_GPR_PCIE_CLK_REQ_OVERRIDE
    enabled by imx6_pcie_enable_ref_clk()

As far as I can tell, these uses are identical before and after
d0a75c791f98 ("PCI: imx6: Factor out ref clock disable to match
enable").

> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> Reviewed-by: Frank Li <Frank.Li@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 413db182ce9f..ab2c97a8c327 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -599,10 +599,9 @@ static int imx_pcie_attach_pd(struct device *dev)
>  
>  static int imx6sx_pcie_enable_ref_clk(struct imx_pcie *imx_pcie, bool enable)
>  {
> -	if (enable)
> -		regmap_clear_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR12,
> -				  IMX6SX_GPR12_PCIE_TEST_POWERDOWN);
> -
> +	regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR12,
> +			   IMX6SX_GPR12_PCIE_TEST_POWERDOWN,
> +			   enable ? 0 : IMX6SX_GPR12_PCIE_TEST_POWERDOWN);
>  	return 0;
>  }
>  
> @@ -631,19 +630,20 @@ static int imx8mm_pcie_enable_ref_clk(struct imx_pcie *imx_pcie, bool enable)
>  {
>  	int offset = imx_pcie_grp_offset(imx_pcie);
>  
> -	if (enable) {
> -		regmap_clear_bits(imx_pcie->iomuxc_gpr, offset, IMX8MQ_GPR_PCIE_CLK_REQ_OVERRIDE);
> -		regmap_set_bits(imx_pcie->iomuxc_gpr, offset, IMX8MQ_GPR_PCIE_CLK_REQ_OVERRIDE_EN);
> -	}
> -
> +	regmap_update_bits(imx_pcie->iomuxc_gpr, offset,
> +			   IMX8MQ_GPR_PCIE_CLK_REQ_OVERRIDE,
> +			   enable ? 0 : IMX8MQ_GPR_PCIE_CLK_REQ_OVERRIDE);
> +	regmap_update_bits(imx_pcie->iomuxc_gpr, offset,
> +			   IMX8MQ_GPR_PCIE_CLK_REQ_OVERRIDE_EN,
> +			   enable ? IMX8MQ_GPR_PCIE_CLK_REQ_OVERRIDE_EN : 0);
>  	return 0;
>  }
>  
>  static int imx7d_pcie_enable_ref_clk(struct imx_pcie *imx_pcie, bool enable)
>  {
> -	if (!enable)
> -		regmap_set_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR12,
> -				IMX7D_GPR12_PCIE_PHY_REFCLK_SEL);
> +	regmap_update_bits(imx_pcie->iomuxc_gpr, IOMUXC_GPR12,
> +			   IMX7D_GPR12_PCIE_PHY_REFCLK_SEL,
> +			   enable ? 0 : IMX7D_GPR12_PCIE_PHY_REFCLK_SEL);
>  	return 0;
>  }
>  
> -- 
> 2.37.1
>