linux-kernel - Re: [PATCH v1] PCI: dwc: Clean up some unnecessary codes in dw_pcie_suspend

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20241107111334.n23ebkbs3uhxivvm@thinkpad>
Date: Thu, 7 Nov 2024 11:13:34 +0000
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Richard Zhu <hongxing.zhu@....com>
Cc: jingoohan1@...il.com, bhelgaas@...gle.com, lpieralisi@...nel.org,
	kw@...ux.com, robh@...nel.org, frank.li@....com,
	imx@...ts.linux.dev, kernel@...gutronix.de,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] PCI: dwc: Clean up some unnecessary codes in
 dw_pcie_suspend_noirq()

On Thu, Nov 07, 2024 at 04:44:55PM +0800, Richard Zhu wrote:
> Before sending PME_TURN_OFF, don't test the LTSSM stat. Since it's safe
> to send PME_TURN_OFF message regardless of whether the link is up or
> down. So, there would be no need to test the LTSSM stat before sending
> PME_TURN_OFF message.
> 

What is the incentive to send PME_Turn_Off when link is not up?

> Remove the L2 poll too, after the PME_TURN_OFF message is sent out.
> Because the re-initialization would be done in dw_pcie_resume_noirq().
> 

As Krishna explained, host needs to wait until the endpoint acks the message
(just to give it some time to do cleanups). Then only the host can initiate
D3Cold. It matters when the device supports L2.

- Mani

> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  .../pci/controller/dwc/pcie-designware-host.c | 20 ++++---------------
>  1 file changed, 4 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index f86347452026..64c49adf81d2 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -917,7 +917,6 @@ static int dw_pcie_pme_turn_off(struct dw_pcie *pci)
>  int dw_pcie_suspend_noirq(struct dw_pcie *pci)
>  {
>  	u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> -	u32 val;
>  	int ret = 0;
>  
>  	/*
> @@ -927,23 +926,12 @@ 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;
>  
> -	/* 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 (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;
> -
> -		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;
> -		}
>  	}
>  
>  	dw_pcie_stop_link(pci);
> -- 
> 2.37.1
> 

-- 
மணிவண்ணன் சதாசிவம்