linux-kernel - Re: [PATCH v3 3/6] PCI: imx6: Workaround i.MX95 PCIe may not exit L23 ready

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Message-ID: <4qrfkx3ckywcbk7qbjplal5j7v6sjs3zebeehe5dnrgjz2ej2t@krdwjb4xm2sx>
Date: Wed, 9 Apr 2025 22:13:36 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Hongxing Zhu <hongxing.zhu@....com>
Cc: Frank Li <frank.li@....com>, 
	"l.stach@...gutronix.de" <l.stach@...gutronix.de>, "lpieralisi@...nel.org" <lpieralisi@...nel.org>, 
	"kw@...ux.com" <kw@...ux.com>, "robh@...nel.org" <robh@...nel.org>, 
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>, "shawnguo@...nel.org" <shawnguo@...nel.org>, 
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>, "kernel@...gutronix.de" <kernel@...gutronix.de>, 
	"festevam@...il.com" <festevam@...il.com>, "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "imx@...ts.linux.dev" <imx@...ts.linux.dev>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/6] PCI: imx6: Workaround i.MX95 PCIe may not exit
 L23 ready

On Tue, Apr 08, 2025 at 03:02:42AM +0000, Hongxing Zhu wrote:
> > -----Original Message-----
> > From: Hongxing Zhu
> > Sent: 2025年4月3日 11:23
> > To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > Cc: Frank Li <frank.li@....com>; l.stach@...gutronix.de; lpieralisi@...nel.org;
> > kw@...ux.com; robh@...nel.org; bhelgaas@...gle.com;
> > shawnguo@...nel.org; s.hauer@...gutronix.de; kernel@...gutronix.de;
> > festevam@...il.com; linux-pci@...r.kernel.org;
> > linux-arm-kernel@...ts.infradead.org; imx@...ts.linux.dev;
> > linux-kernel@...r.kernel.org
> > Subject: RE: [PATCH v3 3/6] PCI: imx6: Workaround i.MX95 PCIe may not exit
> > L23 ready
> > 
> > > -----Original Message-----
> > > From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > > Sent: 2025年4月2日 23:18
> > > To: Hongxing Zhu <hongxing.zhu@....com>
> > > Cc: Frank Li <frank.li@....com>; l.stach@...gutronix.de;
> > > lpieralisi@...nel.org; kw@...ux.com; robh@...nel.org;
> > > bhelgaas@...gle.com; shawnguo@...nel.org; s.hauer@...gutronix.de;
> > > kernel@...gutronix.de; festevam@...il.com; linux-pci@...r.kernel.org;
> > > linux-arm-kernel@...ts.infradead.org; imx@...ts.linux.dev;
> > > linux-kernel@...r.kernel.org
> > > Subject: Re: [PATCH v3 3/6] PCI: imx6: Workaround i.MX95 PCIe may not
> > > exit L23 ready
> > >
> > > On Wed, Apr 02, 2025 at 07:59:26AM +0000, Hongxing Zhu wrote:
> > > > > -----Original Message-----
> > > > > From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > > > > Sent: 2025年4月2日 15:08
> > > > > To: Hongxing Zhu <hongxing.zhu@....com>
> > > > > Cc: Frank Li <frank.li@....com>; l.stach@...gutronix.de;
> > > > > lpieralisi@...nel.org; kw@...ux.com; robh@...nel.org;
> > > > > bhelgaas@...gle.com; shawnguo@...nel.org; s.hauer@...gutronix.de;
> > > > > kernel@...gutronix.de; festevam@...il.com;
> > > > > linux-pci@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> > > > > imx@...ts.linux.dev; linux-kernel@...r.kernel.org
> > > > > Subject: Re: [PATCH v3 3/6] PCI: imx6: Workaround i.MX95 PCIe may
> > > > > not exit L23 ready
> > > > >
> > > > > On Fri, Mar 28, 2025 at 11:02:10AM +0800, Richard Zhu wrote:
> > > > > > ERR051624: The Controller Without Vaux Cannot Exit L23 Ready
> > > > > > Through Beacon or PERST# De-assertion
> > > > >
> > > > > Is it possible to share the link to the erratum?
> > > > >
> > > > Sorry, the erratum document isn't ready to be published yet.
> > > > > >
> > > > > > When the auxiliary power is not available, the controller cannot
> > > > > > exit from
> > > > > > L23 Ready with beacon or PERST# de-assertion when main power is
> > > > > > not removed.
> > > > > >
> > > > >
> > > > > I don't understand how the presence of Vaux affects the controller.
> > > > > Same goes for PERST# deassertion. How does that relate to Vaux? Is
> > > > > this erratum for a specific endpoint behavior?
> > > > IMHO I don't know the exact details of the power supplies in this IP design.
> > > > Refer to my guess , maybe the beacon detect or wake-up logic in
> > > > designs is  relied on the status of SYS_AUX_PWR_DET signals in this case.
> > >
> > > Can you please try to get more details? I couldn't understand the errata.
> > >
> > Sure. Will contact designer and try to get more details.
> Hi Mani:
> Get some information from designs, the internal design logic is relied on the
>  status of SYS_AUX_PWR_DET signal to handle the low power stuff.
> So, the SYS_AUX_PWR_DET is required to be 1b'1 in the SW workaround.
> 

Ok. So due to the errata, when the link enters L23 Ready state, it cannot
transition to L3 when Vaux is not available. And the workaround requires setting
SYS_AUX_PWR_DET bit?

IIUC, the issue here is that the controller is not able to detect the presence
of Vaux in the L23 Ready state. So it relies on the SYS_AUX_PWR_DET bit. But
even in that case, how would you support the endpoint *with* Vaux?

- Mani

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