linux-kernel - Re: [PATCH v3 1/3] PCI: dwc: Fix resume failure if no EP is connected on some platforms

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Message-ID: <ca93bfaa-0b7e-4335-87e0-5f4133efad6a@kernel.org>
Date: Mon, 9 Dec 2024 17:49:43 +0900
From: Damien Le Moal <dlemoal@...nel.org>
To: Richard Zhu <hongxing.zhu@....com>, jingoohan1@...il.com,
 bhelgaas@...gle.com, lpieralisi@...nel.org, kw@...ux.com,
 manivannan.sadhasivam@...aro.org, robh@...nel.org, frank.li@....com,
 quic_krichai@...cinc.com
Cc: imx@...ts.linux.dev, kernel@...gutronix.de, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] PCI: dwc: Fix resume failure if no EP is connected
 on some platforms

On 12/9/24 16:39, 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.
> 
> Call 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.
> 
> Fixes: 4774faf854f5 ("PCI: dwc: Implement generic suspend/resume functionality")
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> Reviewed-by: Frank Li <Frank.Li@....com>
> ---
>  .../pci/controller/dwc/pcie-designware-host.c | 30 +++++++++----------
>  1 file changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index f882b11fd7b94..11563402c571b 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -982,23 +982,23 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
>  	if (dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKCTL) & PCI_EXP_LNKCTL_ASPM_L1)
>  		return 0;
>  
> -	if (dw_pcie_get_ltssm(pci) <= DW_PCIE_LTSSM_DETECT_ACT)
> -		return 0;
> -
> -	if (pci->pp.ops->pme_turn_off)
> -		pci->pp.ops->pme_turn_off(&pci->pp);
> -	else
> -		ret = dw_pcie_pme_turn_off(pci);
> +	/* Only send out PME_TURN_OFF when PCIE link is up */
> +	if (dw_pcie_get_ltssm(pci) > DW_PCIE_LTSSM_DETECT_ACT) {
> +		if (pci->pp.ops->pme_turn_off)
> +			pci->pp.ops->pme_turn_off(&pci->pp);
> +		else
> +			ret = dw_pcie_pme_turn_off(pci);
>  
> -	if (ret)
> -		return ret;
> +		if (ret)
> +			return ret;

Same comment as for patch 3. This "if (ret) return ret;" can go inside the else.
It is harmless, but there is also no point in having it here.

>  
> -	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;
> +		}
>  	}
>  
>  	if (pci->pp.ops->deinit)


-- 
Damien Le Moal
Western Digital Research