From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Niklas Schnelle <niks@kernel.org>
Cc: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>,
"Bjorn Helgaas" <bhelgaas@google.com>,
linux-pci@vger.kernel.org, "Rob Herring" <robh@kernel.org>,
"Krzysztof Wilczy??ski" <kw@linux.com>,
"Maciej W . Rozycki" <macro@orcam.me.uk>,
"Jonathan Cameron" <Jonathan.Cameron@huawei.com>,
"Alexandru Gagniuc" <mr.nuke.me@gmail.com>,
"Krishna chaitanya chundru" <quic_krichai@quicinc.com>,
"Srinivas Pandruvada" <srinivas.pandruvada@linux.intel.com>,
"Rafael J . Wysocki" <rafael@kernel.org>,
linux-pm@vger.kernel.org,
"Smita Koralahalli" <Smita.KoralahalliChannabasappa@amd.com>,
linux-kernel@vger.kernel.org,
"Daniel Lezcano" <daniel.lezcano@linaro.org>,
"Amit Kucheria" <amitk@kernel.org>,
"Zhang Rui" <rui.zhang@intel.com>,
"Christophe JAILLET" <christophe.jaillet@wanadoo.fr>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>
Subject: Re: [PATCH] PCI/portdrv: Disable bwctrl service if port is fixed at 2.5 GT/s
Date: Mon, 9 Dec 2024 17:42:10 +0200 [thread overview]
Message-ID: <20241209154210.GL4955@black.fi.intel.com> (raw)
In-Reply-To: <20241207-fix_bwctrl_thunderbolt-v1-1-b711f572a705@kernel.org>
On Sat, Dec 07, 2024 at 07:44:09PM +0100, Niklas Schnelle wrote:
> Trying to enable bwctrl on a Thunderbolt port causes a boot hang on some
> systems though the exact reason is not yet understood. As per the spec
> Thunderbolt PCIe Downstream Ports have a fake Max Link Speed of 2.5 GT/s
> (USB4 v2 sec 11.2.1):
>
> "Max Link Speed field in the Link Capabilities Register set to 0001b
> (data rate of 2.5 GT/s only).
> Note: These settings do not represent actual throughput.
> Throughput is implementation specific and based on the USB4 Fabric
> performance."
>
> More generally if 2.5 GT/s is the only supported link speed there is no
> point in throtteling as this is already the lowest possible PCIe speed
> so don't advertise the capability stopping bwctrl from being probed on
> these ports.
>
> Link: https://lore.kernel.org/linux-pci/Z1R4VNwCOlh9Sg9n@wunner.de/
> Fixes: 665745f27487 ("PCI/bwctrl: Re-add BW notification portdrv as PCIe BW controller")
> Tested-by: Niklas Schnelle <niks@kernel.org>
> Signed-off-by: Niklas Schnelle <niks@kernel.org>
Makes sense to me,
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
next prev parent reply other threads:[~2024-12-09 15:42 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-07 18:44 [PATCH] PCI/portdrv: Disable bwctrl service if port is fixed at 2.5 GT/s Niklas Schnelle
2024-12-07 19:12 ` Niklas Schnelle
2024-12-09 12:59 ` Ilpo Järvinen
2024-12-09 15:42 ` Mika Westerberg [this message]
2024-12-10 10:05 ` Lukas Wunner
2024-12-10 20:45 ` Niklas Schnelle
2024-12-11 7:57 ` Lukas Wunner
2024-12-11 13:07 ` Ilpo Järvinen
2024-12-12 9:08 ` Lukas Wunner
2024-12-12 9:17 ` Niklas Schnelle
2024-12-12 12:32 ` Lukas Wunner
2024-12-12 14:12 ` Niklas Schnelle
2024-12-12 20:40 ` Niklas Schnelle
2024-12-13 8:37 ` Lukas Wunner
2024-12-16 6:57 ` Mika Westerberg
2024-12-11 17:14 ` Jonathan Cameron
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