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

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Message-ID:
 <AS8PR04MB867639DD98B14369CCC1704A8C3D2@AS8PR04MB8676.eurprd04.prod.outlook.com>
Date: Tue, 10 Dec 2024 02:29:52 +0000
From: Hongxing Zhu <hongxing.zhu@....com>
To: Damien Le Moal <dlemoal@...nel.org>, "jingoohan1@...il.com"
	<jingoohan1@...il.com>, "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"lpieralisi@...nel.org" <lpieralisi@...nel.org>, "kw@...ux.com"
	<kw@...ux.com>, "manivannan.sadhasivam@...aro.org"
	<manivannan.sadhasivam@...aro.org>, "robh@...nel.org" <robh@...nel.org>,
	Frank Li <frank.li@....com>, "quic_krichai@...cinc.com"
	<quic_krichai@...cinc.com>
CC: "imx@...ts.linux.dev" <imx@...ts.linux.dev>, "kernel@...gutronix.de"
	<kernel@...gutronix.de>, "linux-pci@...r.kernel.org"
	<linux-pci@...r.kernel.org>, "linux-kernel@...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()

> -----Original Message-----
> From: Damien Le Moal <dlemoal@...nel.org>
> Sent: 2024年12月9日 16:48
> To: Hongxing 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
> <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.
Hi Damien:
Okay, thanks.
BTW, I'm considering that the use-case of #1 patch had been covered by #3
 commit already.
To be simple, how about drop the #1 patch, re-format the codes, and add one
 Fixes tag into #3?

Best Regards
Richard Zhu
> 
> >
> > -		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