[U-Boot] [PATCH v2 1/2] doc: README.fuse: Add an example on how to use the fuse API on mx6q

[Benoît Thébaudeau]

Hi Fabio,

On Friday, December 20, 2013 9:46:37 PM, Fabio Estevam wrote:
> From: Fabio Estevam <fabio.estevam at freescale.com>
> 
> When using the fuse API in U-boot user must calculate the 'bank' and 'word'
> values.
> 
> Provide a real example on how to calculate such values for the mx6q.
> 
> Signed-off-by: Fabio Estevam <fabio.estevam at freescale.com>
> ---
> Changes since v1:
> - Move the example into doc/README.imx6
> 
>  doc/README.imx6 | 57
>  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 57 insertions(+)
> 
> diff --git a/doc/README.imx6 b/doc/README.imx6
> index 513a06e..728b32c 100644
> --- a/doc/README.imx6
> +++ b/doc/README.imx6
> @@ -8,3 +8,60 @@ SoC.
>  
>  1.1 MAC Address: It is stored in fuse bank 4, with the 32 lsbs in word 2 and
>  the
>      16 msbs in word 3.
> +
> +Example:
> +
> +For reading the MAC address fuses on a MX6Q:
> +
> +- The MAC address are stored in two fuse addresses (the fuse addresses are
                     ^ ^
                     'is' or 'fuses are'

> +described in the Fusemap Descriptions table from the mx6q Reference Manual):
> +
> +0x620[31:0] - MAC_ADDR[31:0]
> +0x630[15:0] - MAC_ADDR[47:32]
> +
> +In order to use the fuse API, we need to pass the bank and word values,
> which
> +are calculated as below:
> +
> +Fuse address for the lower MAC address: 0x620
> +Base address for the fuses: 0x400
> +
> +(0x620 - 0x400)/0x10 = 0x22 = 34 decimal
> +
> +As the fuses are arranged in banks of 8 words:
> +
> +34 / 8 = 4 and the remainder is 2, so in this case:
> +
> +bank = 4
> +word = 2
> +
> +And the U-boot command would be:
> +
> +=> fuse read 4 2
> +Reading bank 4:
> +
> +Word 0x00000002: 9f027772
> +
> +Doing the same for the upper MAC address:
> +
> +Fuse address for the upper MAC address: 0x630
> +Base address for the fuses: 0x400
> +
> +(0x630 - 0x400)/0x10 = 0x23 = 35 decimal
> +
> +As the fuses are arranged in banks of 8 words:
> +
> +35 / 8 = 4 and the remainder is 3, so in this case:
> +
> +bank = 4
> +word = 3
> +
> +And the U-boot command would be:
> +
> +=> fuse read 4 3
> +Reading bank 4:
> +
> +Word 0x00000003: 00000004
> +
> +,which matches the ethaddr value:
> +=> echo ${ethaddr}
> +00:04:9f:02:77:72

Good. As we said earlier, you could also add:
 - 'fuse read 4 2 2' as an example to read the whole MAC address at once,
 - a reference to '46.5 OCOTP Memory Map/Register Definition' in the RM also
   giving these bank/word pairs.

> --

Best regards,
Benoît