Linux/AM3359: MMC 1-bit data transfer mode

Gilberto Ermacovitch

Prodigy 210 points

Part Number: AM3359

Tool/software: Linux

Is it possible to use the Default SD mode 1-bit data transfer mode on MMC0?

If so, I think we need to remove the MMC_CAP_4_BIT_DATA or MMC_CAP_8_BIT_DATA flags from the am335x_mmc[].caps field.

Thanks

Gilberto

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

The software team have been notified. They will respond here.

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

TI__Guru**** 393215 points

Note that you will not be able to boot from MMC0 if you don't have all 4 data bits connected.

0 Gilberto Ermacovitch over 8 years ago in reply to Biser Gatchev-XID

Prodigy 210 points

We do have all four lines connected. However, we intend to use the CD/DAT3 line to detect the insertion/removal of the sdcard.

0 Biser Gatchev-XID over 8 years ago in reply to Gilberto Ermacovitch

TI__Guru**** 393215 points

The MMC driver in the Processor SDK uses a GPIO for card detect, (mechanical switch on the card cage), so I'm not sure how you can achieve this.

0 Gilberto Ermacovitch over 8 years ago in reply to Biser Gatchev-XID

Prodigy 210 points

Yes. I am aware of that. If we use 1-bit data transfer mode, the DAT3 line can be configured as GPIO2_26 and used for card detect. Our card cage does not have the switch.

0 Kemal R. Shakir over 8 years ago in reply to Gilberto Ermacovitch

TI__Guru 55345 points

Hello Gilberto,

To enable the MMC 1-bit data transfer you have to unset the MMC_CAP_4_BIT_DATA and MMC_CAP_8_BIT_DATA flags both. To do this set-up the bus-width device property of the node.
bus-width: Number of data lines, can be <1>, <4>, or <8>, default <1>

Best regards,
Kemal

0 Gilberto Ermacovitch over 8 years ago in reply to Kemal R. Shakir

Prodigy 210 points

Thanks
Now the second part of my question:
The CD-DAT3 pin from the SDcard is connected to pin F17. Normally this his pin is mmc0_dat3(mode 0) . In mode 7 it is gpio2_26.
Can I use pin F17 in mode 7 ( gpio2_26) and configure it as the card detection pin in the sdcard driver?
am335x_mmc[0].gpio_cd = GPIO_TO_PIN(2, 26);
BR

0 Kemal R. Shakir over 8 years ago in reply to Gilberto Ermacovitch

TI__Guru 55345 points

Yes. Mux F17 to mode 7 and reflect this change in nod's cd-gpios property.

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Linux/AM3359: MMC 1-bit data transfer mode