linux-kernel - Re: [PATCH v7 3/3] PCI: dwc: Add no_pme_handshake flag and skip PME_Turn

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Message-ID: <0d37ef61-4407-470b-975d-5f7a147f7f10@foss.st.com>
Date: Wed, 3 Dec 2025 11:09:06 +0100
From: Christian Bruel <christian.bruel@...s.st.com>
To: <zhangsenchuan@...incomputing.com>, <bhelgaas@...gle.com>,
        <mani@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
        <lpieralisi@...nel.org>, <kwilczynski@...nel.org>, <robh@...nel.org>,
        <p.zabel@...gutronix.de>, <jingoohan1@...il.com>,
        <gustavo.pimentel@...opsys.com>, <linux-pci@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <mayank.rana@....qualcomm.com>, <shradha.t@...sung.com>,
        <krishna.chundru@....qualcomm.com>, <thippeswamy.havalige@....com>,
        <inochiama@...il.com>, <Frank.li@....com>
CC: <ningyu@...incomputing.com>, <linmin@...incomputing.com>,
        <pinkesh.vaghela@...fochips.com>, <ouyanghui@...incomputing.com>
Subject: Re: [PATCH v7 3/3] PCI: dwc: Add no_pme_handshake flag and skip
 PME_Turn_Off broadcast

Hello,

On 12/2/25 10:04, zhangsenchuan@...incomputing.com wrote:
> From: Senchuan Zhang <zhangsenchuan@...incomputing.com>
> 
> The ESWIN EIC7700 SoC lacks hardware support for the L2/L3 low-power
> link states. It cannot enter the L2/L3 ready state through the
> PME_Turn_Off/PME_To_Ack handshake protocol. To address this, add a
> no_pme_handshake flag skip PME_Turn_Off broadcast and link state check
> code, other driver can reuse this flag if meet the similar situation.

What about testing !PME_SUPPORT in the PM Capabilities Register,
or just re-use the struct pci_dev pme_support flag ?

Regards,

> 
> Signed-off-by: Yu Ning <ningyu@...incomputing.com>
> Signed-off-by: Yanghui Ou <ouyanghui@...incomputing.com>
> Signed-off-by: Senchuan Zhang <zhangsenchuan@...incomputing.com>
> ---
>   drivers/pci/controller/dwc/pcie-designware-host.c | 4 ++++
>   drivers/pci/controller/dwc/pcie-designware.h      | 1 +
>   2 files changed, 5 insertions(+)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 372207c33a85..8302bc7a6cbf 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -1168,6 +1168,9 @@ 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->no_pme_handshake)
> +		goto stop_link;
> +
>   	if (pci->pp.ops->pme_turn_off) {
>   		pci->pp.ops->pme_turn_off(&pci->pp);
>   	} else {
> @@ -1194,6 +1197,7 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
>   	 */
>   	udelay(1);
> 
> +stop_link:
>   	dw_pcie_stop_link(pci);
>   	if (pci->pp.ops->deinit)
>   		pci->pp.ops->deinit(&pci->pp);
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 31685951a080..e8057db303d0 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -549,6 +549,7 @@ struct dw_pcie {
>   	 * use_parent_dt_ranges to true to avoid this warning.
>   	 */
>   	bool			use_parent_dt_ranges;
> +	bool			no_pme_handshake;
>   };
> 
>   #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp)
> --
> 2.25.1
>