Tegra SDHCI UHS-I support

Hi all,

this series implements UHS-I signaling for the Tegra SDHCI host, which mainly means putting a proper tuning sequence in place.

I've tested this on Jetson TK1 and got the following speed results, where mmcblk0 is the on-board eMMC and mmcblk1 is a micro SDXC card:

Without series applied:
hdparm -t /dev/mmcblk0
Timing buffered disk reads: 110 MB in 3.05 seconds = 36.02 MB/sec
hdparm -t /dev/mmcblk1
Timing buffered disk reads: 56 MB in 3.01 seconds = 18.63 MB/sec

With series applied:
hdparm -t /dev/mmcblk0
Timing buffered disk reads: 236 MB in 3.00 seconds = 78.58 MB/sec
hdparm -t /dev/mmcblk1
Timing buffered disk reads: 102 MB in 3.04 seconds = 33.51 MB/sec

Tegra 30 does support UHS-I speeds too, but currently has problems when lowering the card voltage, which is needed in order to switch to UHS-I signaling. I have some more patches to fix this, but they need a bit more cleanup, with them applied the gains on Tegra30 are similar to the results above.

For now the gains are limited to Tegra124+, with no regressions on Tegra30 and Tegra20.

V2 fixes some minor style problems and is rebased on top of mmc/next. This means it enables the same tuning logic on Tegra210 also. I don't have a way to test this myself, so any testing on Tegra210 much appreciated.

Regards,
Lucas

Lucas Stach (5):
mmc: tegra: implement module external clock change
mmc: tegra: disable SPI_MODE_CLKEN
mmc: tegra: implement UHS tuning
mmc: tegra: enable UHS-I modes
mmc: tegra: use correct accessor for misc ctrl register

 drivers/mmc/host/sdhci-tegra.c | 166 ++++++++++++++++++++++++++++++++++-------
 1 file changed, 138 insertions(+), 28 deletions(-)

2.5.0