linux-kernel - Re: [PATCH v1 2/4] PCI: dwc: Add quirk to fix hang issue when send out PME_Turn

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Message-ID: <xq6ojgyh5tpm4zbpymb2wvtf4at3xq7bai3ztuublgh63e7qdn@vfxan6mew3os>
Date: Sat, 31 May 2025 23:20:15 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Richard Zhu <hongxing.zhu@....com>
Cc: jingoohan1@...il.com, frank.li@....com, l.stach@...gutronix.de, 
	lpieralisi@...nel.org, kw@...ux.com, robh@...nel.org, bhelgaas@...gle.com, 
	shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de, 
	festevam@...il.com, linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	imx@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/4] PCI: dwc: Add quirk to fix hang issue when send
 out PME_Turn_Off Msg TLP

On Tue, Apr 08, 2025 at 02:52:19PM +0800, Richard Zhu wrote:
> When no endpoint is connected on i.MX7D PCIe, chip would be freeze when do
> the dummy write in dw_pcie_pme_turn_off() to issue a PME_Turn_Off Msg TLP.
> 
> Add one quirk to issue the PME_Turn_Off only when link is up to avoid
> this problem on the PME_Turn_Off handshake broken platform, for example
> the i.MX7D.
> 

Why do we need to send PME_Turn_Off if there is no endpoint connected? We should
skip PME_Turn_Off and L2/L3 Ready transitions in that case.

- Mani

> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  .../pci/controller/dwc/pcie-designware-host.c    | 16 +++++++++++-----
>  drivers/pci/controller/dwc/pcie-designware.h     |  1 +
>  2 files changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 0817df5b8a59..a62bf7e0ade8 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -956,12 +956,18 @@ 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 (pci->pp.ops->pme_turn_off) {
> -		pci->pp.ops->pme_turn_off(&pci->pp);
> +	if (dw_pcie_get_ltssm(pci) <= DW_PCIE_LTSSM_DETECT_WAIT &&
> +	    dwc_check_quirk(pci, QUIRK_NOLINK_NOPME)) {
> +		/* Don't send the PME_TURN_OFF when link is down. */
> +		;
>  	} else {
> -		ret = dw_pcie_pme_turn_off(pci);
> -		if (ret)
> -			return ret;
> +		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 (!dwc_check_quirk(pci, QUIRK_NOL2POLL_IN_PM)) {
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 05fe654d7761..d752af660e95 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -283,6 +283,7 @@
>  #define DMA_LLP_MEM_SIZE		PAGE_SIZE
>  
>  #define QUIRK_NOL2POLL_IN_PM		BIT(0)
> +#define QUIRK_NOLINK_NOPME		BIT(1)
>  #define dwc_check_quirk(pci, val)	(pci->quirk_flag & val)
>  
>  struct dw_pcie;
> -- 
> 2.37.1
> 

-- 
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