Re: [PATCH v4 12/18] PCI: rcar-gen4: Recover the Root Port on link down

[sashiko-bot@kernel.org]

> On R-Car, the controller's reset requests (smlh_req_rst_not,
> link_req_rst_not) arrive on intreq_pcim_sub, the interrupt the MSIs are
> demultiplexed from, so DBI is read as soon as the link goes down. On
> R-Car S4 that is a hazard: DBI accesses issued within a few hundred
> microseconds of an unexpected link down do not complete and hang the
> host. In testing, the first Root Port config read after powering off
> the link partner hung unless delayed by ~300 us.
> 
> Check the APP reset status in the interrupt handler before DBI is
> touched. When a reset request is latched, flag the controller as
> needing reinitialization, which masks the sources, ack the request and
> schedule recovery work. The work calls pci_host_handle_link_down() on
> the Root Port, which runs the AER-style recovery and resets the
> controller through reset_root_port(), holding a reference on the port.
> If the Root Port is absent when the work runs, reset the controller
> [ ... ]
> recovery can run once the system thaws. Disarm Root Port events during
> suspend and re-arm them in .post_init() after resume has set up the
> link, so taking the link down for suspend does not start recovery.
> 
> Signed-off-by: Koichiro Den <den@valinux.co.jp>

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

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Sashiko AI review · https://sashiko.dev/#/patchset/20261015033103.3076869-1-den@valinux.co.jp?part=12