linux-kernel - Re: [PATCH 4/8] PCI: dwc: qcom: Update ICC & OPP votes based upon the requested speed

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20250219182746.GA226108@bhelgaas>
Date: Wed, 19 Feb 2025 12:27:46 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Jingoo Han <jingoohan1@...il.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>,
	Johannes Berg <johannes@...solutions.net>,
	Jeff Johnson <jjohnson@...nel.org>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	mhi@...ts.linux.dev, linux-wireless@...r.kernel.org,
	ath11k@...ts.infradead.org, quic_jjohnson@...cinc.com,
	quic_pyarlaga@...cinc.com, quic_vbadigan@...cinc.com,
	quic_vpernami@...cinc.com, quic_mrana@...cinc.com
Subject: Re: [PATCH 4/8] PCI: dwc: qcom: Update ICC & OPP votes based upon
 the requested speed

On Wed, Feb 19, 2025 at 11:28:47PM +0530, Krishna Chaitanya Chundru wrote:
> On 2/19/2025 3:37 AM, Bjorn Helgaas wrote:
> > On Mon, Feb 17, 2025 at 12:04:11PM +0530, Krishna Chaitanya Chundru wrote:
> > > QCOM PCIe controllers needs to disable ASPM before initiating link
> > > re-train. So as part of pre_bw_scale() disable ASPM and as part of
> > > post_scale_bus_bw() enable ASPM back.
> > 
> > s/needs/need/
> > 
> > Why does Qcom need to disable ASPM?  Is there a PCIe spec restriction
> > about this that should be applied to all PCIe host bridges?  Or is
> > this a Qcom defect?
> > 
> It is QCOM controller issue, PCIe spec doesn't mention to disable ASPM.

OK.  I'm a little concerned that disabling/enabling
PCIE_LINK_STATE_ALL might clobber preferences set by drivers of
downstream devices, but I guess ...

Maybe we could add a comment in the code about this being done to work
around some Qcom issue so that browsers of
pci_enable_link_state_locked() don't get the idea that this needs to
be done generically.

Bjorn