linux-kernel - Re: [PATCH v2] PCI: dwc: Clean up some unnecessary codes in dw_pcie_suspend

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Message-ID: <ZzdjSO/jjdu/aF7J@lizhi-Precision-Tower-5810>
Date: Fri, 15 Nov 2024 10:05:44 -0500
From: Frank Li <Frank.li@....com>
To: Richard Zhu <hongxing.zhu@....com>
Cc: jingoohan1@...il.com, bhelgaas@...gle.com, lpieralisi@...nel.org,
	kw@...ux.com, manivannan.sadhasivam@...aro.org, robh@...nel.org,
	imx@...ts.linux.dev, kernel@...gutronix.de,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI: dwc: Clean up some unnecessary codes in
 dw_pcie_suspend_noirq()

On Fri, Nov 15, 2024 at 05:03:21PM +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.
>
> Only dump the message when ltssm_stat is not in DETECT and POLL.
> In the other words, there isn't a notification when no endpoint is
> connected at all.
>
> When the endpoint is connected and after PME_TURN_OFF is issued. Just
> print out one information instead of an error and exit, if the link
> doesn't entry DW_PCIE_LTSSM_L2_IDLE stat. Since the recovery would be
> done in the following closely dw_pcie_resume_noirq().
>
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> ---
>  .../pci/controller/dwc/pcie-designware-host.c | 37 ++++++++++---------
>  drivers/pci/controller/dwc/pcie-designware.h  |  1 +
>  2 files changed, 21 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index f7ceeb785fb0..c2053555c44b 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -927,23 +927,26 @@ 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) {
> -		/* Only send out PME_TURN_OFF when PCIE link is up */
> -		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 (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;
> -		}
> +	ret = read_poll_timeout(dw_pcie_get_ltssm, val, val == DW_PCIE_LTSSM_L2_IDLE,

val == DW_PCIE_LTSSM_L2_IDLE || val <= DW_PCIE_LTSSM_DETECT_WAIT

it will avoid wait 10ms when no link up

> +				PCIE_PME_TO_L2_TIMEOUT_US/10,
> +				PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
> +	if (ret && (val > DW_PCIE_LTSSM_DETECT_WAIT))
> +		/* Only dump message when ltssm_stat isn't in DETECT and POLL */
> +		dev_info(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
> +	else
> +		/*
> +		 * Refer to r6.0, sec 5.3.3.2.1, software should wait at least
> +		 * 100ns after L2/L3 Ready before turning off refclock and
> +		 * main power. It's harmless too when no endpoint connected.
> +		 */
> +		udelay(1);
>  	}
>
>  	dw_pcie_stop_link(pci);
> @@ -952,7 +955,7 @@ int dw_pcie_suspend_noirq(struct dw_pcie *pci)
>
>  	pci->suspended = true;
>
> -	return ret;
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(dw_pcie_suspend_noirq);
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 347ab74ac35a..bf036e66717e 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -330,6 +330,7 @@ enum dw_pcie_ltssm {
>  	/* Need to align with PCIE_PORT_DEBUG0 bits 0:5 */
>  	DW_PCIE_LTSSM_DETECT_QUIET = 0x0,
>  	DW_PCIE_LTSSM_DETECT_ACT = 0x1,
> +	DW_PCIE_LTSSM_DETECT_WAIT = 0x6,
>  	DW_PCIE_LTSSM_L0 = 0x11,
>  	DW_PCIE_LTSSM_L2_IDLE = 0x15,
>
> --
> 2.37.1
>