Re: [RFC PATCH] scsi: ufs: core: Allow error recovery before the device W-LUN exists

[Asdlerto Korry]

> I'm a bit curious why the first link startup fails, while
> the link startup after a reset and restore doesn't.
> Shouldn't these two flows be identical?
> I think the driver is designed on the assumption that the
> basic init must succeed, and that only a re-init can make
> recovery possible.

Hi Peter,

Thanks for the question, you are right. I went back to my notes:
the first init failure was caused by the board, not by the core.

The vendor device tree of this phone has the UFS VCC and VCCQ
supplies (PM7325 LDO7 and LDO9) without regulator-allow-set-load,
so regulator_set_load() from the UFS driver is a no-op and both LDOs
stay in low-power mode. Under the load of the first transfers the
device does not answer the NOP OUT, the host sees
TCx_REPLAY_TIMER_EXPIRED, and the PA error / LINERESET storm I
described only starts after that. With regulator-allow-set-load and
an HPM initial mode on those regulators, the first init succeeds
and the error handler is never needed.

Also, my claim that the device always comes up after the reset was
too strong: in my tests the second link startup succeeded, but
ufshcd_device_init() did not always complete.

So please drop this RFC. The races Sashiko pointed out are another
reason not to remove that check. Sorry for the noise, and thanks
for the review.

Asdlerto