mci: add eMMC DDR52 support

The maximum card frequency that can be configured by barebox currently
is 50MHz for SD and 52MHz for eMMC. Higher speed modes require runtime
voltage switching or tuning sequences, which are not yet implemented.

Only exception is eMMC's DDR52: This mode was first introduced with
MMC 4.4 and can be used even at 3.3V.

This commit adds DDR52 support to the core. This introduces no functional
change, because host controllers must opt-in by setting the appropriate
host capabilities. In cases where it's enabled, bus width determination
happens as usual and then if possible, the resulting bus width will be
attempted with DDR. If that fails, we revert back to SDR.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20230418093040.1865982-4-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

0 files changed, 0 insertions, 0 deletions