[U-Boot] [PATCH 0/2] am335x_boneblack: Enable fastboot flash support

[Lukasz Majewski]

Hi Sam,

> Standard and recommended way to upgrade the firmware is DFU. But DFU
> has extremely low transmission speed (around 150 KiB/sec), thus it's
> a bad fit for flashing big images (like rootfs). Low DFU speed is
> mostly due to next reasons (kudos to Ruslan Bilovol for
> investigation): 1. DFU works only via EP0, per DFU specification [1].
> But AM335x doesn't have DMA for EP0, according to AM335x TRM [2]: from
>     section 16.2:
> 
>       "The CPPI DMA can be used to service Endpoints 1 to 15 not
>        Endpoint 0. CPU access method is used to service Endpoint 0
>        transactions."
> 
>  2. Max transmission packet size via EP0 is 64 bytes, whereas for
> other endpoints max transmission packet size is 512 bytes

DFU was (and still is) supposed to work on all devices - even those
with very tiny resources (like st microcontrollers).

According to USB spec, EP0 is mandatory, so that is the reason for
using it as a common denominator.

Just for the record - fastboot is one of the options here. 

For BBB you may want to look at "dfu tftp" - which uses ETH's tftp
protocol with dfu backend. It is supposed to be a remedy for problem
described above.

More information at:
./doc/README.dfutftp


Of course I also don't mind using fastboot - it depends on your use
case.

> 
> fastboot specification [3], on the other hand, says nothing about
> which EP should be used (and I see that EP1 is used on BBB board). So
> let's enable fastboot flash support on BeagleBone Black board to
> provide a better way to flash big images via USB.
> 
> [1] www.usb.org/developers/docs/devclass_docs/DFU_1.1.pdf
> [2] www.ti.com/lit/ug/spruh73p/spruh73p.pdf
> [3]
> https://android.googlesource.com/platform/system/core/+/master/fastboot/README.md
> 
> Sam Protsenko (2):
>   omap: Fix AM335x build with enabled fastboot flash
>   configs: am335x_boneblack: Enable fastboot flash capability
> 
>  arch/arm/mach-omap2/utils.c        | 2 ++
>  configs/am335x_boneblack_defconfig | 2 ++
>  2 files changed, 4 insertions(+)
> 




Best regards,

Lukasz Majewski

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