linux-kernel - Re: [PATCH 07/15] PCI: brcmstb: Add control of rescal reset

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Date:   Wed, 20 May 2020 09:27:47 +0200
From:   Philipp Zabel <pza@...gutronix.de>
To:     Jim Quinlan <james.quinlan@...adcom.com>
Cc:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:PCI NATIVE HOST BRIDGE AND ENDPOINT DRIVERS" 
        <linux-pci@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/15] PCI: brcmstb: Add control of rescal reset

Hi Jim,

On Tue, May 19, 2020 at 04:34:05PM -0400, Jim Quinlan wrote:
> From: Jim Quinlan <jquinlan@...adcom.com>
> 
> Some STB chips have a special purpose reset controller named
> RESCAL (reset calibration).  This commit adds the control
> of RESCAL as well as the ability to start and stop its
> operation for PCIe HW.
> 
> Signed-off-by: Jim Quinlan <jquinlan@...adcom.com>
> ---
>  drivers/pci/controller/pcie-brcmstb.c | 81 ++++++++++++++++++++++++++-
>  1 file changed, 80 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> index 2c470104ba38..0787e8f6f7e5 100644
> --- a/drivers/pci/controller/pcie-brcmstb.c
> +++ b/drivers/pci/controller/pcie-brcmstb.c
[...]
> @@ -1100,6 +1164,21 @@ static int brcm_pcie_probe(struct platform_device *pdev)
>  		dev_err(&pdev->dev, "could not enable clock\n");
>  		return ret;
>  	}
> +	pcie->rescal = devm_reset_control_get_shared(&pdev->dev, "rescal");
> +	if (IS_ERR(pcie->rescal)) {
> +		if (PTR_ERR(pcie->rescal) == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;
> +		pcie->rescal = NULL;

This is effectively an optional reset control, so it is better to use:
↵
	pcie->rescal = devm_reset_control_get_optional_shared(&pdev->dev,
							      "rescal");↵
	if (IS_ERR(pcie->rescal))
		return PTR_ERR(pcie->rescal);

> +	} else {
> +		ret = reset_control_deassert(pcie->rescal);
> +		if (ret)
> +			dev_err(&pdev->dev, "failed to deassert 'rescal'\n");
> +	}

reset_control_* can handle rstc == NULL parameters for optional reset
controls, so this can be done unconditionally:

	ret = reset_control_deassert(pcie->rescal);↵
	if (ret)↵
		dev_err(&pdev->dev, "failed to deassert 'rescal'\n");↵

Is rescal handled by the reset-brcmstb-rescal driver? Since that only
implements the .reset op, I would expect reset_control_reset() here.
Otherwise this looks like it'd be missing a reset_control_assert in
remove.

regards
Philipp