Re: [PATCH v2] mtd: nand: marvell: Fix clock resource by adding a register clock

[Boris Brezillon <boris.brezillon@bootlin.com>]

+Rob and the DT ML for the DT bindings changes.

On Wed,  7 Mar 2018 17:13:16 +0100
Gregory CLEMENT <gregory.clement@bootlin.com> wrote:

> On Armada 7K/8K we need to explicitly enable the register clock. This
> clock is optional because not all the SoCs using this IP need it but at
> least for Armada 7K/8K it is actually mandatory.
> 
> The binding documentation is updated accordingly.
> 
> Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
> ---
> Changelog:
> v1-> v2
> 
>  - Removed the unnecessary IS_ERR() call
>  - Skip the reg clock only if it is not present by checking "-ENOENT"
>  - Add a label for uninitializing the reg clock.
>  
>  .../devicetree/bindings/mtd/marvell-nand.txt       |  6 +++++-
>  drivers/mtd/nand/marvell_nand.c                    | 24 ++++++++++++++++++----
>  2 files changed, 25 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/mtd/marvell-nand.txt b/Documentation/devicetree/bindings/mtd/marvell-nand.txt
> index c08fb477b3c6..4ee9813bf88f 100644
> --- a/Documentation/devicetree/bindings/mtd/marvell-nand.txt
> +++ b/Documentation/devicetree/bindings/mtd/marvell-nand.txt
> @@ -14,7 +14,11 @@ Required properties:
>  - #address-cells: shall be set to 1. Encode the NAND CS.
>  - #size-cells: shall be set to 0.
>  - interrupts: shall define the NAND controller interrupt.
> -- clocks: shall reference the NAND controller clock.
> +- clocks: shall reference the NAND controller clocks, the second one is
> +  optional but needed for the Armada 7K/8K SoCs
> +- clock-names: mandatory if there is a second clock, in this case the
> +   name must be "core" for the first clock and "reg" for the second
> +   one

Still think we should not enforce the order, and I proposed a simple
solution for that in my previous review:

	nfc->ecc_clk = devm_clk_get(&pdev->dev, "core");
	if (PTR_ERR(nfc->ecc_clk) == -ENOENT)
		nfc->ecc_clk = devm_clk_get(&pdev->dev, NULL);

	if (IS_ERR(nfc->ecc_clk))
		return PTR_ERR(nfc->ecc_clk);

>  - marvell,system-controller: Set to retrieve the syscon node that handles
>    NAND controller related registers (only required with the
>    "marvell,armada-8k-nand[-controller]" compatibles).
> diff --git a/drivers/mtd/nand/marvell_nand.c b/drivers/mtd/nand/marvell_nand.c
> index 2196f2a233d6..072e23635375 100644
> --- a/drivers/mtd/nand/marvell_nand.c
> +++ b/drivers/mtd/nand/marvell_nand.c
> @@ -321,6 +321,7 @@ struct marvell_nfc {
>  	struct device *dev;
>  	void __iomem *regs;
>  	struct clk *ecc_clk;
> +	struct clk *reg_clk;

There's a kernel-doc header describing the marvell_nfc fields, could
you add an entry for reg_clk?

>  	struct completion complete;
>  	unsigned long assigned_cs;
>  	struct list_head chips;
> @@ -2747,12 +2748,24 @@ static int marvell_nfc_probe(struct platform_device *pdev)
>  	if (ret)
>  		return ret;
>  
> +	nfc->reg_clk = devm_clk_get(&pdev->dev, "reg");
> +	if (PTR_ERR(nfc->reg_clk) != -ENOENT) {
> +		if (!IS_ERR(nfc->reg_clk)) {
> +			ret = clk_prepare_enable(nfc->reg_clk);
> +			if (ret)
> +				goto unprepare_clk;

I already suggested to move the devm_clk_get(&pdev->dev, "reg") before
the clk_prepare_enable(nfc->ecc_clk) one to simplify the error path.

> +		} else {
> +			ret = PTR_ERR(nfc->reg_clk);
> +			goto unprepare_clk;
> +		}
> +	}

So nfc->reg_clk stays assigned to -ENOENT if the clk is not present, and
clk_disable_unprepare() will manipulate an invalid pointer when called
from the error or ->remove() path.

Could be addressed/simplified with something like that:

	/*
	 * The register clk is only required on armada 8k. By assigning
	 * ->reg_clk to NULL when -ENOENT is returned, we make sure all
	 * clk_prepare_enable()/clk_disable_unprepare() calls work
	 * correctly even if the clk is missing.
	 */
	nfc->reg_clk = devm_clk_get(&pdev->dev, "reg");
	if (PTR_ERR(nfc->reg_clk) == -ENOENT)
		nfc->reg_clk = NULL;

	if (IS_ERR(nfc->reg_clk))
		return PTR_ERR(nfc->reg_clk);

	...

	ret = clk_prepare_enable(nfc->reg_clk);
	if (ret)
		goto unprepare_ecc_clk;


> +
>  	marvell_nfc_disable_int(nfc, NDCR_ALL_INT);
>  	marvell_nfc_clear_int(nfc, NDCR_ALL_INT);
>  	ret = devm_request_irq(dev, irq, marvell_nfc_isr,
>  			       0, "marvell-nfc", nfc);
>  	if (ret)
> -		goto unprepare_clk;
> +		goto unprepare_clk_reg;
>  
>  	/* Get NAND controller capabilities */
>  	if (pdev->id_entry)
> @@ -2763,22 +2776,24 @@ static int marvell_nfc_probe(struct platform_device *pdev)
>  	if (!nfc->caps) {
>  		dev_err(dev, "Could not retrieve NFC caps\n");
>  		ret = -EINVAL;
> -		goto unprepare_clk;
> +		goto unprepare_clk_reg;
>  	}
>  
>  	/* Init the controller and then probe the chips */
>  	ret = marvell_nfc_init(nfc);
>  	if (ret)
> -		goto unprepare_clk;
> +		goto unprepare_clk_reg;
>  
>  	platform_set_drvdata(pdev, nfc);
>  
>  	ret = marvell_nand_chips_init(dev, nfc);
>  	if (ret)
> -		goto unprepare_clk;
> +		goto unprepare_clk_reg;
>  
>  	return 0;
>  
> +unprepare_clk_reg:
> +	clk_disable_unprepare(nfc->reg_clk);
>  unprepare_clk:

Please rename the label (unprepare_clk -> unprepare_ecc_clk).

>  	clk_disable_unprepare(nfc->ecc_clk);
>  
> @@ -2796,6 +2811,7 @@ static int marvell_nfc_remove(struct platform_device *pdev)
>  		dma_release_channel(nfc->dma_chan);
>  	}
>  
> +	clk_disable_unprepare(nfc->reg_clk);
>  	clk_disable_unprepare(nfc->ecc_clk);
>  
>  	return 0;



-- 
Boris Brezillon, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com