[U-Boot] [PATCH v1] cmd/sf: probe flash with speed of last known flash or speed from devicetree

[Hannes Schmelzer <hannes@schmelzer.or.at>]

On 08/24/2016 12:35 PM, Vignesh R wrote:
> Hi,
Hi Vignesh,
> On Wednesday 24 August 2016 03:35 PM, Hannes Schmelzer wrote:
>> During probing flashes on the spi bus using the "sf probe" command, a
>> maybe existing flash (from fdt) is unbound and removed to force the
>> 'spi_flash_probe_bus_cs' really scanning the bus.
>>
>> Today the bus is probed with speed 0, this triggers several fall-back
>> mechanism (mostly in the low-level drivers) to catch the impossible zero
>> speed.
>> Result of this is, that the spi-flash runs at very low speed depending
>> on the minimum given by low-level driver/hardware.
>>
>> Values like 'spi-max-frequency' from devicetree are ignored totally
>> today.
>>
>> This commit changes as following:
>> - if there was already some flash binding in devicetree (having some
>>    spi-max-frequency within) speed is taken from it
>> - if no flash binding was present for speed the 'spi-max-frequency' from
>>    the responsible spi node is taken.
>>
>> Signed-off-by: Hannes Schmelzer <oe5hpm@oevsv.at>
>
> With commit 96907c0fe50a8 ("dm: spi: Read default speed and mode values
> from DT") sf probe picks spi-max-frequency from DT if not specified as
> argument.
>
> But when sf probe is called second time, the command fails to pick up
> speed from DT. This is because flash node is unbound from the SPI
> controller children nodes. Below patch should fix this issue:
> https://patchwork.ozlabs.org/patch/659979/

sry ... i didn't took notice about this patch at the beginning of mine. 
Just reviewed and tested it.

The named patch makes things a bit better but not good.
Speed for flash still has no relationship to 'spi-max-frequency' from 
the spi-bus nor with a maybe defined flash in dts.

Rather the #define CONFIG_ENV_SPI_MAX_HZ is used.

But for my thinking the way we should walk is having more and more and 
finally (if possible) all within device-tree and dynamic configuration 
rather than in #define ...

cheers,
Hannes