描述

The SDIO controller requires that the SDIO clockbe active in order to write to the software resets CMD andDAT. If the SDIO clock is not active, the controller andinterconnect willhang.

解决方案

Work-around Detail:Host Driver Software Flow.

Optional: CMD and DAT resets:
This option precedes the Host Driver flow, below, if the Host Driver issues CMD and DAT resets during host controller initialization. If Host Driver issues only Soft Reset for ALL during host controller initialization, then this option is not needed. SDIO clock is needed to clear soft reset CMD and DAT bits.

1) Enable the SDIO clock.
2) Perform CMD and DAT resets. Write 1 then 0 to sdio.Clock_Control_Timeout_control_Software_reset[25, 26].

Example: Host Driver Flow:

1) Wait for card insertion. Configure Card Detect Interrupt.
2) On card insertion, perform Soft Reset ALL. Write 1 then 0 to sdio.Clock_Control_Timeout_control_Software_reset[24].
3) Enable host interrupts and Enable the SDIO Clock.
4) Initialize SD Card.

Soft Reset for ALL:
Asserting the Software_Reset_for_All will reset all of the SDIO registers, including the sdio.Clock_Control_Timeout_control_Software_reset register itself. After the reset, the Driver shall enable the SDIO clock.

Updated August 20, 2012