linux-kernel - Re: [PATCH v3] PCI: keystone: Fix race condition when initializing PHYs

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Date: Tue, 9 Jan 2024 12:41:59 +0900
From: Krzysztof Wilczyński <kw@...ux.com>
To: Siddharth Vadapalli <s-vadapalli@...com>
Cc: lpieralisi@...nel.org, robh@...nel.org, bhelgaas@...gle.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, ilpo.jarvinen@...ux.intel.com,
	vigneshr@...com, r-gunasekaran@...com, srk@...com
Subject: Re: [PATCH v3] PCI: keystone: Fix race condition when initializing
 PHYs

Hello,

> The PCI driver invokes the PHY APIs using the ks_pcie_enable_phy()
> function. The PHY in this case is the Serdes. It is possible that the
> PCI instance is configured for 2 lane operation across two different
> Serdes instances, using 1 lane of each Serdes. In such a configuration,
> if the reference clock for one Serdes is provided by the other Serdes,
> it results in a race condition. After the Serdes providing the reference
> clock is initialized by the PCI driver by invoking its PHY APIs, it is
> not guaranteed that this Serdes remains powered on long enough for the
> PHY APIs based initialization of the dependent Serdes. In such cases,
> the PLL of the dependent Serdes fails to lock due to the absence of the
> reference clock from the former Serdes which has been powered off by the
> PM Core.
> 
> Fix this by obtaining reference to the PHYs before invoking the PHY
> initialization APIs and releasing reference after the initialization is
> complete.

Applied to controller/keystone, thank you!

[1/1] PCI: keystone: Fix race condition when initializing PHYs
      https://git.kernel.org/pci/pci/c/c12ca110c613

	Krzysztof