[PATCH] PCI: meson: Fix PERST# timing by asserting reset before LTSSM enable

[sashiko-bot at kernel.org]

> On warm reboot, the PCIe controller's LTSSM starts link training
> immediately if PERST# is already deasserted from the previous boot.
> The driver then pulses PERST# for only 500us, which is too short to
> properly reset the endpoint device that has already started training.
> 
> Fix by moving the PERST# assert/deassert pulse BEFORE enabling LTSSM,
> so the endpoint gets a clean reset cycle before link training begins.
> 
> This was found on Amlogic G12B (A311D) with NVMe on an M.2 slot.
> Cold boot worked because POR held PERST# low; warm reboot did not.
> The fix was confirmed on a Banana Pi CM4 with Waveshare IO base board.
> 
> Signed-off-by: Gowtham Kudupudi <gowtham at ferryfair.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260614015620.20432-1-gowtham@ferryfair.com?part=1