From: Bjorn Helgaas <helgaas@kernel.org>
To: liziyao@uniontech.com
Cc: "Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Krzysztof Wilczyński" <kwilczynski@kernel.org>,
"Manivannan Sadhasivam" <mani@kernel.org>,
"Rob Herring" <robh@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
niecheng1@uniontech.com, zhanjun@uniontech.com,
guanwentao@uniontech.com, "Kexy Biscuit" <kexybiscuit@aosc.io>,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
loongarch@lists.linux.dev,
"Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>,
stable@vger.kernel.org, "Lain Fearyncess Yang" <fsf@live.com>,
"Ayden Meng" <aydenmeng@yeah.net>,
"Mingcong Bai" <jeffbai@aosc.io>,
"Xi Ruoyao" <xry111@xry111.site>,
"Huacai Chen" <chenhuacai@kernel.org>
Subject: Re: [PATCH v5] PCI: loongson: Override PCIe bridge supported speeds for Loongson-3C6000 series
Date: Tue, 13 Jan 2026 16:06:47 -0600 [thread overview]
Message-ID: <20260113220647.GA783058@bhelgaas> (raw)
In-Reply-To: <20260113-loongson-pci1-v5-1-264c9b4a90ab@uniontech.com>
On Tue, Jan 13, 2026 at 03:58:48PM +0800, Ziyao Li via B4 Relay wrote:
> From: Ziyao Li <liziyao@uniontech.com>
>
> Older steppings of the Loongson-3C6000 series incorrectly report the
> supported link speeds on their PCIe bridges (device IDs 0x3c19, 0x3c29)
> as only 2.5 GT/s, despite the upstream bus supporting speeds from
> 2.5 GT/s up to 16 GT/s.
>
> As a result, since commit 774c71c52aa4 ("PCI/bwctrl: Enable only if more
> than one speed is supported"), bwctrl will be disabled if there's only
> one 2.5 GT/s value in vector `supported_speeds`.
>
> Also, amdgpu reads the value by pcie_get_speed_cap() in amdgpu_device_
> partner_bandwidth(), for its dynamic adjustment of PCIe clocks and
> lanes in power management. We hope this can prevent similar problems
> in future driver changes (similar checks may be implemented in other
> GPU, storage controller, NIC, etc. drivers).
Don't split amdgpu_device_partner_bandwidth() across lines; that makes
it hard to copy and grep for it.
Bjorn
prev parent reply other threads:[~2026-01-13 22:06 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-13 7:58 [PATCH v5] PCI: loongson: Override PCIe bridge supported speeds for Loongson-3C6000 series Ziyao Li via B4 Relay
2026-01-13 22:06 ` Bjorn Helgaas [this message]
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