linux-kernel - Re: [PATCH 1/5 V2] PCI: define a function to check and wait till port finish DPC handling

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Date:   Sun, 27 Sep 2020 07:23:59 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Ethan Zhao <haifeng.zhao@...el.com>
Cc:     bhelgaas@...gle.com, oohall@...il.com, ruscur@...sell.cc,
        lukas@...ner.de, andriy.shevchenko@...ux.intel.com,
        stuart.w.hayes@...il.com, mr.nuke.me@...il.com,
        mika.westerberg@...ux.intel.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, pei.p.jia@...el.com,
        ashok.raj@...ux.intel.com, sathyanarayanan.kuppuswamy@...el.com
Subject: Re: [PATCH 1/5 V2] PCI: define a function to check and wait till
 port finish DPC handling

> +#ifdef CONFIG_PCIE_DPC
> +static inline bool pci_wait_port_outdpc(struct pci_dev *pdev)
> +{
> +	u16 cap = pdev->dpc_cap, status;
> +	u16 loop = 0;
> +
> +	if (!cap) {
> +		pci_WARN_ONCE(pdev, !cap, "No DPC capability initiated\n");
> +		return false;
> +	}
> +	pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status);
> +	pci_dbg(pdev, "DPC status %x, cap %x\n", status, cap);
> +	while (status & PCI_EXP_DPC_STATUS_TRIGGER && loop < 100) {
> +		msleep(10);
> +		loop++;
> +		pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status);
> +	}
> +	if (!(status & PCI_EXP_DPC_STATUS_TRIGGER)) {
> +		pci_dbg(pdev, "Out of DPC %x, cost %d ms\n", status, loop*10);
> +		return true;
> +	}
> +	pci_dbg(pdev, "Timeout to wait port out of DPC status\n");
> +	return false;
> +}

I don't think that there is any good reason to have this as an
inline function.