Hello, When testing the IOT2050 Advanced M.2 platform with Linux CIP 6.1 we came across a breakage in the probing of the Keystone PCI driver (drivers/phy/ti/pci-keystone.c). This probing was working correctly in the previous version we were using, v5.10. In order to debug this we changed over to mainline Linux and bissecting lead us to find that commit e611f8cd8717 is the culprit, and with it applied we get the following messages: [ 10.954597] phy-am654 910000.serdes: Failed to enable PLL [ 10.960153] phy phy-910000.serdes.3: phy poweron failed --> -110 [ 10.967485] keystone-pcie 5500000.pcie: failed to enable phy [ 10.973560] keystone-pcie: probe of 5500000.pcie failed with error -110 This timeout is occuring in serdes_am654_enable_pll(), called from the phy_ops .power_on() hook. Due to the nature of the error messages and the contents of the commit we believe that this is due to an unidentified race condition in the probing of the Keystone PCI driver when enabling the PHY PLLs, since changes in the workqueue the deferred probing runs on should not affect if probing works or not. To further support the existence of a race condition, commit 86bfbb7ce4f6 (a scheduler commit) fixes probing, most likely unintentionally meaning that the problem may arise in the future again. One possible explanation is that there are pre-requisites for enabling the PLL that are not being met when e611f8cd8717 is applied; to see if this is the case help from people more familiar with the hardware details would be useful. As official support specifically for the IOT2050 Advanced M.2 platform was introduced in Linux v6.3 (so in the middle of the commits mentioned above) all of our testing was done with the latest mainline DeviceTree with [1] applied on top. This is being reported as a regression even though technically things are working with the current state of mainline since we believe the current fix to be an unintended by-product of other work. #regzbot introduced: e611f8cd8717 [1]: https://lore.kernel.org/all/cover.1699087938.git.jan.kiszka@xxxxxxxxxxx/
