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mmc: omap_hsmmc: Enable HSPE bit for high speed cards

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HSMMC IP on AM33xx need a special setting to handle High-speed cards.
Other platforms like TI81xx, OMAP4 may need this as-well. This depends
on the HSMMC IP timing closure done for the high speed cards.

From AM335x TRM (SPRUH73F - 18.3.12 Output Signals Generation):

The MMC/SD/SDIO output signals can be driven on either falling edge or
rising edge depending on the SD_HCTL[2] HSPE bit. This feature allows
to reach better timing performance, and thus to increase data transfer
frequency.

There are few pre-requisites for enabling the HSPE bit
- Controller should support High-Speed-Enable Bit and
- Controller should not be using DDR Mode and
- Controller should advertise that it supports High Speed in
  capabilities register and
- MMC/SD clock coming out of controller > 25MHz

Signed-off-by: Hebbar, Gururaja <[email protected]>
Signed-off-by: Venkatraman S <[email protected]>
Signed-off-by: Chris Ball <[email protected]>
This commit is contained in:
Hebbar, Gururaja 2012-11-19 21:59:58 +05:30 • committed by Chris Ball
commit cd587096c0
3 changed files with 31 additions and 1 deletions
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1
Documentation/devicetree/bindings/mmc/ti-omap-hsmmc.txt
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@ -19,6 +19,7 @@ ti,dual-volt: boolean, supports dual voltage cards
"supply-name" examples are "vmmc", "vmmc_aux" etc
ti,non-removable: non-removable slot (like eMMC)
ti,needs-special-reset: Requires a special softreset sequence
ti,needs-special-hs-handling: HSMMC IP needs special setting for handling High Speed
Example:
mmc1: mmc@0x4809c000 {