On 03/03/2011 04:48 AM, Priyanka Jain wrote:
Timeout counter value is set as DTOCV bits in SYSCTL register For counter value set as timeout, Timeout period = (2^(timeout + 13)) SD Clock cycles
As per 4.6.2.2 section of SD Card specification v2.00, host should cofigure timeout period value to minimum 0.25 sec.
Number of SD Clock cycles for 0.25sec should be minimum (SD Clock/sec * 0.25 sec) SD Clock cycles = (mmc->tran_speed * 1/4) SD Clock cycles
Calculating timeout based on (2^(timeout + 13)) >= mmc->tran_speed * 1/4 Taking log2 both the sides and rounding up to next power of 2 => timeout + 13 = log2(mmc->tran_speed/4) + 1
Signed-off-by: Priyanka Jain Priyanka.Jain@freescale.com Signed-off-by: Andy Fleming afleming@freescale.com Signed-off-by: Kumar Gala galak@kernel.crashing.org Acked-by: Mingkai Hu Mingkai.Hu@freescale.com
Tested on a i.MX51 board.
Tested-by: Stefano Babic sbabic@denx.de
Best regards, Stefano Babic