linux-kernel - Re: [PATCH v7 8/8] PCI: imx: Add the imx8mm pcie support

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Message-ID: <Ybtuo0CzfUhoJwsT@rocinante>
Date:   Thu, 16 Dec 2021 17:51:47 +0100
From:   Krzysztof Wilczyński <kw@...ux.com>
To:     Richard Zhu <hongxing.zhu@....com>
Cc:     l.stach@...gutronix.de, bhelgaas@...gle.com,
        lorenzo.pieralisi@....com, marcel.ziswiler@...adex.com,
        tharvey@...eworks.com, kishon@...com, vkoul@...nel.org,
        robh@...nel.org, galak@...nel.crashing.org, shawnguo@...nel.org,
        linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de,
        linux-imx@....com
Subject: Re: [PATCH v7 8/8] PCI: imx: Add the imx8mm pcie support

Hi Richard,

Apologies for a very late review!  Especially since Lorenzo already took
patches as per:

  https://lore.kernel.org/linux-pci/163965080404.20006.5241609551643501749.b4-ty@arm.com/

However, perhaps it's not too late.

[...]
> @@ -446,6 +452,13 @@ static int imx6_pcie_enable_ref_clk(struct imx6_pcie *imx6_pcie)
>  		break;
>  	case IMX7D:
>  		break;
> +	case IMX8MM:
> +		ret = clk_prepare_enable(imx6_pcie->pcie_aux);
> +		if (ret) {
> +			dev_err(dev, "unable to enable pcie_aux clock\n");
> +			break;
> +		}
> +		break;

You can drop the inner break, it wouldn't do much here, unless this was
intended to be a return?

> @@ -538,6 +559,10 @@ static void imx6_pcie_deassert_core_reset(struct imx6_pcie *imx6_pcie)
>  	case IMX8MQ:
>  		reset_control_deassert(imx6_pcie->pciephy_reset);
>  		break;
> +	case IMX8MM:
> +		if (phy_init(imx6_pcie->phy) != 0)
> +			dev_err(dev, "Waiting for PHY ready timeout!\n");
> +		break;

If the above, you can keep the same style as used throughout the file
already, so it would just simply be:

  if (phy_init(imx6_pcie->phy))

Also, a nitpick: to be consistent with other such messages here, the error
message would be all lower-case letters.

[...]
> @@ -614,6 +639,8 @@ static void imx6_pcie_configure_type(struct imx6_pcie *imx6_pcie)
>  static void imx6_pcie_init_phy(struct imx6_pcie *imx6_pcie)
>  {
>  	switch (imx6_pcie->drvdata->variant) {
> +	case IMX8MM:
> +		break;
>  	case IMX8MQ:

Would it warrant a comment that adds a note there to this single bare
break?  Perhaps this version is not support, lack this particular
functionality, etc.

[...]
> @@ -1089,10 +1122,39 @@ static int imx6_pcie_probe(struct platform_device *pdev)
>  			dev_err(dev, "Failed to get PCIE APPS reset control\n");
>  			return PTR_ERR(imx6_pcie->apps_reset);
>  		}
> +		break;
> +	case IMX8MM:
> +		imx6_pcie->pcie_aux = devm_clk_get(dev, "pcie_aux");
> +		if (IS_ERR(imx6_pcie->pcie_aux))
> +			return dev_err_probe(dev, PTR_ERR(imx6_pcie->pcie_aux),
> +					     "pcie_aux clock source missing or invalid\n");
> +		imx6_pcie->apps_reset = devm_reset_control_get_exclusive(dev,
> +									 "apps");
> +		if (IS_ERR(imx6_pcie->apps_reset)) {
> +			dev_err(dev, "Failed to get PCIE APPS reset control\n");
> +			return PTR_ERR(imx6_pcie->apps_reset);
> +		}
> +
> +		imx6_pcie->phy = devm_phy_get(dev, "pcie-phy");
> +		if (IS_ERR(imx6_pcie->phy)) {
> +			if (PTR_ERR(imx6_pcie->phy) == -EPROBE_DEFER)
> +				return -EPROBE_DEFER;
> +			dev_err(dev, "Failed to get PCIE PHY\n");
> +			return PTR_ERR(imx6_pcie->phy);
> +		}

A question about handling of the -EPROBE_DEFER above: why not to use the
dev_err_probe() helper similarly to the code above and below?  Would there
be something different preventing the use of dev_err_probe() here too?

>  		break;
>  	default:
>  		break;
>  	}
> +	/* Don't fetch the pcie_phy clock, if it has abstract PHY driver */
> +	if (imx6_pcie->phy == NULL) {
> +		imx6_pcie->pcie_phy = devm_clk_get(dev, "pcie_phy");
> +		if (IS_ERR(imx6_pcie->pcie_phy))
> +			return dev_err_probe(dev, PTR_ERR(imx6_pcie->pcie_phy),
> +					     "pcie_phy clock source missing or invalid\n");
> +	}

Thank you for another amazing patch!

	Krzysztof