linux-kernel - Re: [PATCH v3 3/3] PCI: dwc: Clean up some unnecessary codes in dw_pcie_suspend

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Message-ID: <48988ec4-06a9-447b-bdd5-be35f31a5488@kernel.org>
Date: Mon, 9 Dec 2024 17:47:51 +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 3/3] PCI: dwc: Clean up some unnecessary codes in
 dw_pcie_suspend_noirq()

On 12/9/24 16:39, Richard Zhu wrote:
> Before sending PME_TURN_OFF, don't test the LTSSM state. 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 state before sending
> PME_TURN_OFF message.
> 
> Only print the message when ltssm_stat is not in DETECT and POLL.
> In the other words, there isn't an error message when no endpoint is
> connected at all.
> 
> Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> Reviewed-by: Frank Li <Frank.Li@....com>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>  .../pci/controller/dwc/pcie-designware-host.c | 38 +++++++++++--------
>  drivers/pci/controller/dwc/pcie-designware.h  |  1 +
>  2 files changed, 23 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 14e95c2952bbe..02e0e8c255c70 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -982,25 +982,31 @@ 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 (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 is always 0 for the "if (pci->pp.ops->pme_turn_off)" case. So this test of
"if (ret) return ret" should really go inside the "else", and the initialization
of ret to 0 on declaration can be removed too.

>  
> -		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_DETECT_WAIT,
> +				PCIE_PME_TO_L2_TIMEOUT_US/10,
> +				PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
> +	if (ret) {
> +		/* Only dump message when ltssm_stat isn't in DETECT and POLL */
> +		dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
> +		return ret;
>  	}
>  
> +	/*
> +	 * 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);
>  	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 5c14ed2cb91ed..7efcb4af66da3 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,
>  


-- 
Damien Le Moal
Western Digital Research