Re: [PATCH] HID: intel-thc-hid: intel-quickspi: reset touch IC on system resume

[d3z <d3z.the.dev@gmail.com>]

From: Danny D. <d3z.the.dev@gmail.com>

Hi Even,

Good way to split it - "touch IC off" vs "THC power-gated" - so I ran the
reset_tic()-only test you asked for.

I added just reset_tic() to a pristine quickspi_resume(), with none of the
THC reconfig (no thc_spi_*_config, no thc_ltr_*). On the Surface Pro 10,
after an s2idle suspend/resume, the touchscreen does NOT come back - so
reset_tic() alone isn't enough here.

The interesting bit is why. The one new line on resume is:

    intel_quickspi 0000:00:10.0: THC interrupt already unquiesce

That's reset_tic() -> thc_interrupt_quiesce(dev, false) finding
DEVINT_QUIESCE_EN already clear - even though quickspi_suspend() set it in
suspend. thc_regmap is REGCACHE_NONE, so that's the real register, not a
cached value. So the THC port-control state we wrote in suspend is gone
after resume.

That's your second case: the THC itself loses its register context across
s2idle, without ever hitting PM_SUSPEND_MEM. reset_tic()'s SPI exchange
then runs against a THC whose I/O address and read/write config are wiped,
so the reset never completes. Reprogramming those first (like
quickspi_restore(), and like v2 on the no-wake path) is what brings touch
and pen back.

So on the SP10 both are needed - reset the touch IC AND reconfigure the
THC - the full reconfigure looks necessary here.

One note on the log: there's no fresh "Wait RESET_RESPONSE timeout" line
this cycle, but that path is dev_err_once() and the box had ~12h uptime, so
an earlier cycle likely already consumed it.

Thanks,
Danny