AM335x - SD card detection code

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1

Hi all,

I have a custom board that is a modified copy of beaglebone. I am running 3.2.33 kernel.

My problem is that the kernel doesn’t detect the SD Card when its booting. I realized the problem is caused by difference in SD card reader. Beaglebone uses card reader that a card detection switch. The switch is opened (pull-up; hence high) when it is empty, and switch is closed (shorted to ground; low) when card is inserted. In my board, the logic is reversed. I imagined this to be simple modification in the kernel, but cannot find where that card detection config / set-up is. I have looked in board-am335xevm.c file, and still looking around. No luck yet.

Could someone point me to which file to modify? or Is there a flowchart of kernel file chain that would show me which file/function linux kernel calls?

Best regards,

Jinsuk

2

Research CONFIG_BOOT_TRACER

There is also bootchart

both will render an .SVG graphic visualization of the kernel boot process

3

The configuration is present in board-am335xevm.c only,

Go inside function “mmc0_init()”, you will find function calls to “setup_pin_mux()”,

For common mmc pins along with write-protect and card-detect mmc pins. You need to

Change AM33XX_PIN_INPUT_PULLUP => AM33XX_PIN_INPUT_PULLDOWN

Thanks,

Vaibhav

4

Thanks for the help guys. I also posted on TI forum, and they were able to help me.

I needed to edit those two functions in this file /drivers/mmc/host/omap_hsmmc.c

omap_hsmmc_card_detect()

omap_hsmmc_get_cover_state()

Best regards,

Jin

5

Many possibilities, does uboot take SD card?

6

What do you mean by “take”?

Thanks,

Vaibhav

7

Can uboot read any SD card? can you boot uboot from SD card?

8

Yes, certainly. That’s the basic feature.

The boot sequence would be, ROM è MLO è u-boot.img è uImage

Thanks,

Vaibhav