Some of the Renesas R-Car boards need to set the eMMC driver type to type 1 to get stable HS200/400 speeds (HS400 support not upstream yet). Because the eMMC memories are fixed (and thus the drive type), I decided to implement the DT setup in a similar fashion to ACPI [1]. While implementing, I realized that all I did was not Renesas specific but generic, so I ended up putting it into the core. So, whenever the new property (introduced in patch 1) is used, and there is no host driver specific select_drive_strength callback, then the generic callback (introduced in patch 2) is used. An example usage can be found in patch 3. Note that currently only eMMC is handled, but the code is designed for easy SD addition if that ever becomes necessary. A branch for the Salvator-XS board can be found here: git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git renesas/topic/emmc-drive-strength A wiki page describing my test procedure can be found here: http://elinux.org/Tests:eMMC-fixed-drive-strength Looking forward to comments about this approach. All the best, Wolfram [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=51ced59cc02e0d08f61772c888480b9b1749cef1 Wolfram Sang (3): mmc: describe new eMMC binding for fixed driver type mmc: parse new binding for eMMC fixed driver type arm64: renesas: salvator-xs: set driver type for eMMC Documentation/devicetree/bindings/mmc/mmc.txt | 3 +++ .../arm64/boot/dts/renesas/r8a7795-salvator-xs.dts | 4 ++++ drivers/mmc/core/core.c | 28 ++++++++++++++++++---- drivers/mmc/core/host.c | 11 ++++++++- include/linux/mmc/host.h | 2 ++ 5 files changed, 42 insertions(+), 6 deletions(-) -- 2.11.0
