From: Bjorn Helgaas <helgaas@kernel.org>
To: Jim Quinlan <james.quinlan@broadcom.com>
Cc: linux-pci@vger.kernel.org,
"Nicolas Saenz Julienne" <nsaenz@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
"Cyril Brulebois" <kibi@debian.org>,
"Phil Elwell" <phil@raspberrypi.com>,
bcm-kernel-feedback-list@broadcom.com,
"Jim Quinlan" <jim2101024@gmail.com>,
"Florian Fainelli" <florian.fainelli@broadcom.com>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Krzysztof Wilczyński" <kw@linux.com>,
"Rob Herring" <robh@kernel.org>,
"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
<linux-rpi-kernel@lists.infradead.org>,
"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
<linux-arm-kernel@lists.infradead.org>,
"open list" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v7 2/3] PCI: brcmstb: Configure HW CLKREQ# mode appropriate for downstream device
Date: Thu, 9 Nov 2023 16:31:40 -0600 [thread overview]
Message-ID: <20231109223140.GA494906@bhelgaas> (raw)
In-Reply-To: <CA+-6iNxKavvTthcpWeMTu5FfeqZhvMbALK1WwdRqQhivHJFWTQ@mail.gmail.com>
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
WARNING: multiple messages have this Message-ID (diff)
From: Bjorn Helgaas <helgaas@kernel.org>
To: Jim Quinlan <james.quinlan@broadcom.com>
Cc: linux-pci@vger.kernel.org,
"Nicolas Saenz Julienne" <nsaenz@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
"Cyril Brulebois" <kibi@debian.org>,
"Phil Elwell" <phil@raspberrypi.com>,
bcm-kernel-feedback-list@broadcom.com,
"Jim Quinlan" <jim2101024@gmail.com>,
"Florian Fainelli" <florian.fainelli@broadcom.com>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Krzysztof Wilczyński" <kw@linux.com>,
"Rob Herring" <robh@kernel.org>,
"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
<linux-rpi-kernel@lists.infradead.org>,
"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
<linux-arm-kernel@lists.infradead.org>,
"open list" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v7 2/3] PCI: brcmstb: Configure HW CLKREQ# mode appropriate for downstream device
Date: Thu, 9 Nov 2023 16:31:40 -0600 [thread overview]
Message-ID: <20231109223140.GA494906@bhelgaas> (raw)
In-Reply-To: <CA+-6iNxKavvTthcpWeMTu5FfeqZhvMbALK1WwdRqQhivHJFWTQ@mail.gmail.com>
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
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next prev parent reply other threads:[~2023-11-09 22:31 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-09 19:13 [PATCH v7 0/3] PCI: brcmstb: Configure appropriate HW CLKREQ# mode Jim Quinlan
2023-11-09 19:13 ` Jim Quinlan
2023-11-09 19:13 ` [PATCH v7 1/3] dt-bindings: PCI: brcmstb: Add property "brcm,clkreq-mode" Jim Quinlan
2023-11-09 19:13 ` Jim Quinlan
2023-11-09 21:33 ` Bjorn Helgaas
2023-11-09 21:33 ` Bjorn Helgaas
2023-11-09 19:13 ` [PATCH v7 2/3] PCI: brcmstb: Configure HW CLKREQ# mode appropriate for downstream device Jim Quinlan
2023-11-09 19:13 ` Jim Quinlan
2023-11-09 21:27 ` Bjorn Helgaas
2023-11-09 21:27 ` Bjorn Helgaas
2023-11-09 22:06 ` Jim Quinlan
2023-11-09 22:06 ` Jim Quinlan
2023-11-09 22:31 ` Bjorn Helgaas [this message]
2023-11-09 22:31 ` Bjorn Helgaas
2023-11-10 13:01 ` Jim Quinlan
2023-11-10 13:01 ` Jim Quinlan
2023-11-10 14:39 ` Bjorn Helgaas
2023-11-10 14:39 ` Bjorn Helgaas
2023-11-09 19:13 ` [PATCH v7 3/3] PCI: brcmstb: Set higher value for internal bus timeout Jim Quinlan
2023-11-09 19:13 ` Jim Quinlan
2023-11-09 21:27 ` Bjorn Helgaas
2023-11-09 21:27 ` Bjorn Helgaas
2023-11-13 17:36 ` [PATCH v7 0/3] PCI: brcmstb: Configure appropriate HW CLKREQ# mode Florian Fainelli
2023-11-13 17:36 ` Florian Fainelli
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