Re: [PATCH v3 03/18] PCI: rcar-gen4: Check live link status in link_up()

[sashiko-bot@kernel.org]

> rcar_gen4_pcie_link_up() checks link state using SMLH_LINK_UP and
> RDLH_LINK_UP in PCIEINTSTS0. However, these bits do not reflect the live
> link state. On an R-Car S4, after taking down the endpoint, a link-down
> interrupt saw PCIEINTSTS0 = 0x20a000c5 with both bits still set. Even
> after resetting the controller with the LTSSM back in Polling, they read
> 0xa000c5, still set.
> 
> As a result, dw_pcie_link_up() keeps reporting the link as up after it
> has gone down. That defeats the check in dw_pcie_other_conf_map_bus(),
> which is supposed to stop config accesses to downstream devices while
> the link is down, so such accesses go out on the dead link and stall the
> host. It also makes the callback useless for the link-down recovery
> added later, which has to wait for the link to actually come back after
> resetting the controller.
> 
> Keep the APP link-up event check from Figure 104.5 of the R-Car S4
> reference manual, but also require PORT_LINK_DEBUG1 to report the link
> up and not in training, through dw_pcie_link_up_debug_check(). The
> callback then rejects a downed link even if the APP link-up events
> remain latched.
> 
> Clear the APP latches before enabling LTSSM to discard events from a
> previous start, and only read them in .link_up(). RC startup uses
> dw_pcie_wait_for_link() to poll the combined condition.
> 
> Fixes: 0d0c551011df ("PCI: rcar-gen4: Add R-Car Gen4 PCIe controller support for host mode")
> Suggested-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
> Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
> Tested-by: Marek Vasut <marek.vasut+renesas@mailbox.org> # R-Car V4H
> 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/20261006084638.3821710-1-den@valinux.co.jp?part=3