How to control AM437x mmc0_pow pin?

g.f.

Guru 15510 points

Hi,

I have question about AM437x MMC power switch pin(mmc0_pow).

I read AM437x TRM(sruhl7c) page.2553, it seem that MMC_POW is used for MMC/SD card's on/off power supply control.

But there was no information how to control this mmc0_pow pin.

How to control this mmc0_pow pin?

Is there any register to control mmc0_pow pin?

best regards,

g.f.

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

Hi g.f,

This has been asked before about AM335X. Since the AM437X MMC controller is the same, this pin is not used by software.

0 g.f. over 8 years ago in reply to Biser Gatchev-XID

Guru 15510 points

Hi Biser,

Thank you for the reply.

Okay, I understood that this pin are not controlled by software.

But how to use this pin? And in what kind of case MMC_POW is needed?

From the TRM page.2548 Figure 17-1, MMC_POW pin is connected to Power Switch.
So, if user use Power Switch for SD card, MMC_POW pin can be used, is it correct?

Is Power Switch a Load Switch?
If yes, is it right to connect MMC_POW pin to Load Switch's EN pin?

By the way, in what condition will MMC_POW pin will be drive High state?

best regards,
g.f.

0 Biser Gatchev-XID over 8 years ago in reply to g.f.

TI__Guru**** 393215 points

As I pointed out in my first post, there is no usage for this pin. This has been asked to the factory team before and the answer has been the same.

0 g.f. over 8 years ago in reply to Biser Gatchev-XID

Guru 15510 points

Sorry, I don't understand yet.
Do you mean that user should not use this mmc0_pow pin and leave NC or PU/PD externally?

best regards,

g.f.

0 Biser Gatchev-XID over 8 years ago in reply to g.f.

TI__Guru**** 393215 points

I have asked the factory team to provide information, if there is any. What I can say is that this signal has been never used in any of the AM335X or AM437X reference designs. As for the pin, MMC0_POW is an output signal available on 2 pins, and is pinmuxed with signals from other interfaces. It doesn't need anything to be done if it's not used.

0 g.f. over 8 years ago in reply to Biser Gatchev-XID

Guru 15510 points

Hi Biser,

Thank you for the reply and thank you for asking to the factory team.
If there is any information, please tell me.
I understood that this pin doesn't need any process if it's not used.

best regards,
g.f.

0 Biser Gatchev-XID over 8 years ago in reply to g.f.

TI__Guru**** 393215 points

Yes this is correct.

0 Koichiro Tashiro over 8 years ago in reply to Biser Gatchev-XID

TI__Mastermind 21150 points

Hi Biser,

Sorry for jumping-in.
According to above discussion, the mmc0_pow pin has no meaning nor value for users.
Why don’t we simply remove the pin from TRM and DataSheet to avoid such confusion and questions ?

Thanks and regards,
Koichiro

0 Biser Gatchev-XID over 8 years ago in reply to Koichiro Tashiro

TI__Guru**** 393215 points

This is out of my scope of competence.

0 Steve Kipisz over 8 years ago in reply to Biser Gatchev-XID

TI__Genius 15510 points

I should have something to post on Wednesday. I've been asking around.Steve K.

0 Koichiro Tashiro over 8 years ago in reply to Steve Kipisz

TI__Mastermind 21150 points

Hi Steve,

Any news for this ?

Thanks and regards,
Koichiro

0 Steve Kipisz over 8 years ago in reply to Koichiro Tashiro

TI__Genius 15510 points

The SDBP bit in the SD_HCTL register controls this pin. The Linux driver sets/clears this bit. The TRM should be updated with more information.

Steve K.

0 g.f. over 8 years ago in reply to Steve Kipisz

Guru 15510 points

Hi Steve,

Thank you for the reply.

In TRM(spruhl7c) page.2619 "Table 17-36", there are description of SDBP.
It said "If the host controller detects th No card state, this bit is automatically cleared to 0".

If MMC/SD controller detects SD card, does this bit"SDBP" automatically be set to 1 or not?
If it will be set, does MMC0_POW pin goes to High state automatically?

best regards,
g.f.

0 g.f. over 8 years ago in reply to Steve Kipisz

Guru 15510 points

Hi Steve,

I need to answer to my customer.
Can you please answer to the question? And when does TRM will be updated?

best regards,
g.f.

0 JJD over 8 years ago in reply to g.f.

TI__Guru 68890 points

g.f.The SDBP bit will automatically change to 0 if the card detect input indicates no card is present. I will not automatically change to 1 if the card is inserted. This needs to be done with software. Note that on our current EVMs, the card detect goes to a generic GPIO (not the MMCSD card detect signal), so software is in complete control of the power turning on or off.

An update to the TRM isn't scheduled at this time. Probably will be a few months from now.

Regards,

James

0 g.f. over 8 years ago in reply to JJD

Guru 15510 points

Hi Steve,

Thank you for the reply.

I think I understand now but let me ask again to make me sure.

So, SDBP will automatically change to 0 and mmc0_pow pin will be drives to Low if no card is present.
And if card detect goes to GPIO or MMC/SD card detection pin, software need to set SDBP for driving mmc0_pow to HIGH.
This is the way to control the Power on/off of MMC/SD card.

Is my understanding correct?

best regards,
g.f.

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How to control AM437x mmc0_pow pin?