linux-kernel - Re: [PATCH v7 6/7] PCI: qcom: Disable ASPM L0s and remove BDF2SID mapping config for X1E80100 SoC

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Message-ID: <20241030071851.sdm3fu6ecaddoiit@thinkpad>
Date: Wed, 30 Oct 2024 12:48:51 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Johan Hovold <johan@...nel.org>
Cc: Qiang Yu <quic_qianyu@...cinc.com>, vkoul@...nel.org, kishon@...nel.org,
	robh@...nel.org, andersson@...nel.org, konradybcio@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, mturquette@...libre.com,
	sboyd@...nel.org, abel.vesa@...aro.org, quic_msarkar@...cinc.com,
	quic_devipriy@...cinc.com, dmitry.baryshkov@...aro.org,
	kw@...ux.com, lpieralisi@...nel.org, neil.armstrong@...aro.org,
	linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	devicetree@...r.kernel.org, linux-clk@...r.kernel.org,
	johan+linaro@...nel.org, stable@...r.kernel.org
Subject: Re: [PATCH v7 6/7] PCI: qcom: Disable ASPM L0s and remove BDF2SID
 mapping config for X1E80100 SoC

On Wed, Oct 30, 2024 at 08:15:05AM +0100, Johan Hovold wrote:
> On Wed, Oct 30, 2024 at 01:54:59PM +0800, Qiang Yu wrote:
> > On 10/24/2024 2:42 PM, Qiang Yu wrote:
> > > On 10/18/2024 10:06 PM, Johan Hovold wrote:
> 
> > >> Also say something about how L0s is broken so that it is more clear what
> > >> the effect of this patch is. On sc8280xp enabling L0s lead to
> > >> correctable errors for example.
> 
> > > Need more time to confirm the exact reason about disabling L0s.
> > > Will update if get any progress
> 
> > I confirmed with HW team and SW team. L0s is not supported on X1E80100, 
> > it is not fully verified. So we don't want to enable it.
> 
> Thanks for checking. A word about what can happen if not disabling it
> may still be in place (e.g. the link state transition stats in debugfs
> on x1e80100 looked pretty erratic with L0s enabled IIRC).
> 
> Also, are there any Qualcomm platforms that actually support L0s?
> Perhaps we should just disable it everywhere?
> 

Most of the mobile chipsets from Qcom support L0s. It is not supported only on
the compute ones. So we cannot disable it everywhere.

Again, it is not the hw issue but the PHY init sequence not tuned support L0s.

- Mani

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