AM623: uSD Card Detection Without Card Detect

Lawrence Wong

Part Number: AM623

Tool/software:

Customer having problem finding uSD Card Cage that has provision for Card Detect signal. Question is without the dedicated Card Detect signal:

- How does Boot ROM handle this. Poll uSD Card and time out to proceed to next boot option?

- How does Linux detect if a uSD card is insserted? Periodically poll?

Regards,

Lawrence

over 2 years ago

0 Hong Guan64 over 2 years ago

TI__Guru* 78750 points

From "5.4.3.1 SD Card Bootloader Operation" of AM62x TRM
"The MMCSD module depends on proper voltage level on the SD card detect signal (SDCD). If SDCD=1, the ROM will assume the card is not present and will fail the boot mode.The SDCD must be 0 for the ROM to continue to attempt to boot. Card detect using DAT3 is not supported."
Best,
-Hong

0 Lawrence Wong over 2 years ago in reply to Hong Guan64

TI__Genius 16780 points

Hi Hong,

Ok but since the uSD Card Carrier does not have provision for Card Detect switch, the customer would hard wire it to 0. Then what happens to my 2 use cases? especially if no uSD is present?

Regards,

Lawrence

0 Hong Guan64 over 2 years ago in reply to Lawrence Wong

TI__Guru* 78750 points

Let me loop in my colleague for input on your follow-up questions.

0 JJD over 2 years ago in reply to Hong Guan64

TI__Guru* 95381 points

Lawrence, the ROM will attempt to boot if the card detect is sampled active low. If it doesn't find an image (which it won't if no card is detected), it will timeout and move on to the secondary boot source.

i think hong will answer for the kernel action.

James

0 Hong Guan64 over 2 years ago in reply to JJD

TI__Guru* 78750 points

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1301386/processor-sdk-am62x-use-the-mmc2-ports-to-connect-to-sdmmc-uboot-cannot-detect-the-sd-card/4944498#4944498

0 Lawrence Wong over 2 years ago in reply to Hong Guan64

TI__Genius 16780 points

Hi Hong,

Again the probelm is the uSD Card Cage does not have Card Detect Switch. James was able to address the Boot ROM portion, but how does Linux handle if the SDCD is hard wired to GND? How does it detect if a uSD card is insterted? Is there a periodic poll? Does it wait for timeout?

Regards,

Lawrence

0 Hong Guan64 over 2 years ago in reply to Lawrence Wong

TI__Guru* 78750 points

Refer to "broken-cd" property in MMC node as noted in the referenced e2e in my last reply.
https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/Documentation/devicetree/bindings/mmc/mmc-controller.yaml?h=10.00.04#n37
Best,
-Hong

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AM623: uSD Card Detection Without Card Detect