On Thu, 22 Oct 2015 11:57:18 +0900 Jaehoon Chung jh80.chung@samsung.com wrote:
Hi,
On 10/20/2015 10:57 AM, Siarhei Siamashka wrote:
Hello,
Currently SD card support seems to be broken at least on the ODROID-X board in U-Boot v2015.10. Checking older U-Boot releases shows that it used to work in v2014.10, and bisecting points to the commit a276172cf32386c211c75638f6bf3c0d59ba03ba ("arm: exynos: fix the div value for set_mmc_clk"): http://git.denx.de/?p=u-boot.git;a=commitdiff;h=a276172cf32386c211c75638f6bf...
Reverting this commit resolves the problem and the SD card starts working properly.
As an extra test, I also tried to add debugging print at the end of the exynos4_set_mmc_clk() function, so that it calls exynos4_get_mmc_clk() with the original 'dev_index' and reports the resulting mmc clock speed. After reverting the patch, the reported value is 50MHz. Before reverting it, the reported value was 100MHz. This is a Transcend class 6 SDHC card.
Is this enough information or should I check something else?
I will check this..
Thanks a lot! I'm expecting that it should not be very difficult to reproduce the problem. I guess, you just need an old slow SD card for this, which can't handle high clock speeds. The "Error detected in status(0x208002)!" problem has been also reported earlier: http://lists.denx.de/pipermail/u-boot/2015-June/217326.html
But if my SD card is unique enough and you have difficulties reproducing it, then I don't mind debugging the exynos mmc clocking code myself. So please let me know if you can or can't reproduce the bug.
I needs to get more information. I want to know div value passed by argument.
The div value is passed as 1 and decremented to 0.
Frankly speaking, I don't quite like the fact that this adjustment of the divisor is done relatively far from writing it to the hardware register. The point is that we are dealing with two different things here: 1. the divisor in a mathematical sense. 2. the divisor representation as encoded in the hardware register (which is decremented by 1). Confusing between these two may lead to bugs. For example, not adjusting the divisor at all or doing this more than once.