[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20231109223140.GA494906@bhelgaas>
Date: Thu, 9 Nov 2023 16:31:40 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Jim Quinlan <james.quinlan@...adcom.com>
Cc: linux-pci@...r.kernel.org,
Nicolas Saenz Julienne <nsaenz@...nel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
Cyril Brulebois <kibi@...ian.org>,
Phil Elwell <phil@...pberrypi.com>,
bcm-kernel-feedback-list@...adcom.com,
Jim Quinlan <jim2101024@...il.com>,
Florian Fainelli <florian.fainelli@...adcom.com>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
Krzysztof WilczyĆski <kw@...ux.com>,
Rob Herring <robh@...nel.org>,
"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
<linux-rpi-kernel@...ts.infradead.org>,
"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
<linux-arm-kernel@...ts.infradead.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 2/3] PCI: brcmstb: Configure HW CLKREQ# mode
appropriate for downstream device
On Thu, Nov 09, 2023 at 05:06:15PM -0500, Jim Quinlan wrote:
> ...
> BTW, besides the RPi4, I haven't been able to find a Linux platform
> where I can do
>
> echo $POLICY > /sys/module/pcie_aspm/parameters/policy
This sounds like something we should fix. What exactly happens? I
think this should be handled at pcie_aspm_set_policy(), so:
/sys/module/pcie_aspm/parameters/policy doesn't exist (seems
unlikely)?
Returns -EPERM (would indicate aspm_disabled)?
Returns -EINVAL (would indicate $POLICY doesn't match anything in
policy_str[])?
Returns 0 with no action (would indicate $POLICY is the same as the
current aspm_policy)?
> It seems that the FW/ACPI typically locks this down. I did see a
> comment somewhere that
> said that the reason it was locked down is because too many devices
> cannot handle it.
Do you have any details about FW/ACPI locking this down?
aspm_disabled is set by the kernel "pcie_aspm=off" parameter (I assume
you're not referring to this), if the FADT has ACPI_FADT_NO_ASPM set,
or if a host bridge's _OSC is missing or failed (maybe [1] is the
comment you saw?)
These all *should* be unusual cases, so I'd be surprised if you're
tripping over one of these. I would NOT be surprised if we had some
issue in pcie_config_aspm_link() or pcie_set_clkpm() that meant the
policy change didn't work as intended, though.
Bjorn
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/acpi/pci_root.c?id=v6.6#n617
Powered by blists - more mailing lists