linux-imx

sata: ahci-da850: add a workaround for controller instability

We have a use case with the da850 SATA controller where at PLL0
frequency of 456MHz (needed to properly service the LCD controller)
the chip becomes unstable and the hardreset operation is ignored the
first time 50% of times.

The sata core driver already retries to resume the link because some
controllers ignore writes to the SControl register, but just retrying
the resume operation doesn't work - we need to issue he phy/wake reset
again to make it work.

Reimplement ahci_hardreset() in the driver and poke the controller a
couple times before really giving up.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>