Hi,
I need your help in writing a UHS-I driver for OMAP4430.
I would like to know the feasibility in implementing a UHS-I driver (for SD
card) in OMAP4430. (I am using Pandaboard).
The purpose is to have readspeed more than 40MB/s for SD cards (Which as per
the SD card specification 3.01 is possible only in UHS-I mode).
For this I see that OMAP4430 supports 1.8V and DDR50 mode also.
Please let me know your informed opinion about whether UHS-I can be
implemented for Pandaboard.
I am having trouble in switching to UHS-I mode in Pandaboard.
Following are my queries.
I am using an SD card which does support UHS-I mode. (Sandisk UHS Extreme Pro
(45 MB/s quoted speed))
I am trying to switch the card to UHS mode by first sending a ACMD41.
For this I have modified the mmc_send_app_op_cond () in
drivers/mmc/core/sd_ops.c to set the S18R bit.
And in the response from the SD card I see that S18A bit is
set.
After this response response from the SD Card I am sending CMD11 to SD Card.
After receiving the response from SD Card I am changing the SDVS in MMCHS_HCTL
to 0x5 which is for 1.8V.(As per mentioned in the Specification).
However I am not able to read the DLEV as 0xF from PSTATE register as per
mentioned in the OMAP4430 specification.
Please let me know what I might be missing.
Is there is a possbility that we could achieve 40MB/s of read speed in SD mode
without using the UHS-I ?
We see in the spec that it does support upto 48MB/s in DDR mode.
But as per the SD card specification 3.01 DDR mode is supported only in UHS-I
mode.
This is the reason I am trying to switch the card to UHS-I mode.
Please let me know if there is a way to use DDR mode in Pandaboard for SD
card without having to switch to UHS-I to achieve read speeds of around 40MB/s.
with thanks,
V.Manoharan
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