Changes for the eMMC in uboot for am3356.

nilesh kadivar

Intellectual 940 points

Other Parts Discussed in Thread: AM3356

Hi,

We have custom board based on AM3356 processor.

And we want to use eMMC (4 GB -- Based on e•MMC™5.0 standard) on MMC1 port of processor.

We are using u-boot-2014.07-g7e537bf and SDK version ti-processor-sdk-linux-am335x-evm-01.00.00.00.

We want to configure/run eMMC on 4 bit mode as of now from MLO/u-boot. Is there any changes required for eMMC initialization and file reading for mentioned u-boot version for AM3356?

Thanks in advance.

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

No, this should be handled by the ROM code.

0 nilesh kadivar over 9 years ago in reply to Biser Gatchev-XID

Intellectual 940 points

Hi Biser,

Thanks for your reply.

I want to confirm one query on same topic.

If ROM would initialize eMMC then why MLO needs to initialize mmc again in file (arch/arm/cpu/armv7/am33xx/board.c -- cpu_mmc_init Function).

That will call function in file (drivers/mmc/omap_hsmmc.c) and there it initialization with configuration (8bit/4bit,min-max freq,etc.).

Please make me clear in this case.

Note : As mentioned we are using u-boot version u-boot-2014.07-g7e537bf.

Thanks in advance.

0 nilesh kadivar over 9 years ago in reply to nilesh kadivar

Intellectual 940 points

Hi Biser,

Can you please help us?

Regards,

Nilesh

0 Yordan Kovachev over 9 years ago in reply to nilesh kadivar

TI__Guru**** 161600 points

Hi,

Biser is actually correct, if you choose to boot from eMMC, then ROM code performs the basic MMC configuration, so that the SoC can read & load the MLO image.
The configurations you refer to in arch/arm/cpu/armv7/am33xx/board.c & drivers/mmc/omap_hsmmc.c perform additional mmc settings so that the controller can be used later in u-boot (i.e. mmc commands in u-boot). Specifically the omap_hsmmc driver is used for the u-boot MMC commands.

The setting of the bus width (4-bit or 8-bit) is done in omap_hsmmc_set_ios() call. If you wish to force the MMC controller to use 4-bit or 8-bit bus width, you should pass/hardcode the corresponding value 4 or 8 to mmc->bus_width.

Hope this helps.

Best Regards,
Yordan

0 nilesh kadivar over 9 years ago in reply to Yordan Kovachev

Intellectual 940 points

Hi Yordan,

Thanks a lot for your help. Thanks for your clarification. So in this case can i say without any changes in default u-boot code, ROM bootloader will set up eMMC to boot till u-boot and then Kernel.

In kernel to set up eMMC with 8 bit width, I have configured .dts file like below :
&mmc2 {
status = "okay";
vmmc-supply = <&vmmcsd_fixed>;
bus-width = <8>; /*For eMMC 8 bit*/
pinctrl-names = "default", "sleep";
pinctrl-0 = <&mmc2_pins_default>;
pinctrl-1 = <&mmc2_pins_sleep>;
cd-gpios = <&gpio0 6 GPIO_ACTIVE_HIGH>;
ti,non-removable;
}

Is this fine or need to add/remove any more parameters?

Regards,

Nilesh

0 Yordan Kovachev over 9 years ago in reply to nilesh kadivar

TI__Guru**** 161600 points

Hi,

This seems correct.
Just have in mind that you need to mux the gpio0_6 pin correctly, in order to use it in cd-gpios.

Best Regards,
Yordan

0 nilesh kadivar over 9 years ago in reply to Yordan Kovachev

Intellectual 940 points

Thanks Yordan for confirming this.
Thanks a lot.
We have muxed mentioned card detect pin.
But, eMMC is non-removable and it will be on board. It will be detected if its out of reset and in working condition.
SO, cd-gpio (Card Detect gpio) will be required to detect eMMC?

0 Yordan Kovachev over 9 years ago in reply to nilesh kadivar

TI__Guru**** 161600 points

Hi,

It is OK to use the gpio to detect eMMC. What I was trying to say is that you need to set its pinmux in dts.

Best Regards,
Yordan

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Changes for the eMMC in uboot for am3356.