mmc: tegra: update hw tuning process

mmc: tegra: update hw tuning process

This patch includes below HW tuning related fixes.
    configures tuning parameters as per Tegra TRM
    WAR fix for manual tap change
    HW auto-tuning post process

As per Tegra TRM, SDR50 mode tuning execution takes upto maximum
of 256 tuning iterations and SDR104/HS200/HS400 modes tuning
execution takes upto maximum of 128 tuning iterations.

This patch programs tuning control register with maximum tuning
iterations needed based on the timing along with the start tap,
multiplier, and step size used by the HW tuning.

Tegra210 has a known issue of glitch on trimmer output when the
tap value is changed with the trimmer input clock running and the
WAR is to disable card clock before sending tuning command and
after sending tuning command wait for 1usec and issue SW reset
followed by enabling card clock.

This WAR is applicable when changing tap value manually as well.
Tegra SDHCI driver has this implemented correctly for manual tap
change but missing SW reset before enabling card clock during
sending tuning command.

Issuing SW reset during tuning command as a part of WAR and is
applicable in cases where tuning is performed with single step size
for more iterations. This patch includes this fix.

HW auto-tuning finds the best largest passing window and sets the
tap at the middle of the window. With some devices like sandisk
eMMC driving fast edges and due to high tap to tap delay in the
Tegra chipset, auto-tuning does not detect falling tap between the
valid windows resulting in a parital window or a merged window and
the best tap is set at the signal transition which is actually the
worst tap location.

Recommended SW solution is to detect if the best passing window
picked by the HW tuning is a partial or a merged window based on
min and max tap delays found from chip characterization across
PVT and perform tuning correction to pick the best tap.

This patch has implementation of this post HW tuning process for
the tegra hosts that support HW tuning through the callback function
tegra_sdhci_execute_hw_tuning and uses the tuned tap delay.

Tested-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>