linux-kernel - Re: [PATCH v2] PCI: dwc: Fix resume failure if no EP is connected at some platforms

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Message-ID: <20241105233513.GA1495684@bhelgaas>
Date: Tue, 5 Nov 2024 17:35:13 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Richard Zhu <hongxing.zhu@....com>
Cc: kwilczynski@...nel.org, bhelgaas@...gle.com, lorenzo.pieralisi@....com,
	frank.li@....com, mani@...nel.org, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel@...gutronix.de, imx@...ts.linux.dev
Subject: Re: [PATCH v2] PCI: dwc: Fix resume failure if no EP is connected at
 some platforms

On Mon, Jul 22, 2024 at 02:15:13PM +0800, Richard Zhu wrote:
> The dw_pcie_suspend_noirq() function currently returns success directly
> if no endpoint (EP) device is connected. However, on some platforms, power
> loss occurs during suspend, causing dw_resume() to do nothing in this case.
> This results in a system halt because the DWC controller is not initialized
> after power-on during resume.
> 
> Change call to deinit() in suspend and init() at resume regardless of
> whether there are EP device connections or not. It is not harmful to
> perform deinit() and init() again for the no power-off case, and it keeps
> the code simple and consistent in logic.
> ...

> -	ret = read_poll_timeout(dw_pcie_get_ltssm, val, val == DW_PCIE_LTSSM_L2_IDLE,
> -				PCIE_PME_TO_L2_TIMEOUT_US/10,
> -				PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
> -	if (ret) {
> -		dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
> -		return ret;
> +		ret = read_poll_timeout(dw_pcie_get_ltssm, val, val == DW_PCIE_LTSSM_L2_IDLE,
> +					PCIE_PME_TO_L2_TIMEOUT_US/10,
> +					PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
> +		if (ret) {
> +			dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
> +			return ret;
> +		}

Not related to this patch, but what's the reason for waiting for the
link to enter L2?  There are a few other drivers that do this, but
most don't.  Is there something else the driver needs to do after the
link is in L2?

>  	}
>  
>  	if (pci->pp.ops->deinit)
> -- 
> 2.37.1
>