[U-Boot] [PATCH v3 10/16] drivers: mtd: spi: sf_probe: add compatible for spansion spi flash

[Jagan Teki]

On 20 November 2015 at 11:31, Mugunthan V N <mugunthanvnm at ti.com> wrote:
> Jagan
>
> On Thursday 19 November 2015 03:40 PM, Jagan Teki wrote:
>> On 19 November 2015 at 12:35, Mugunthan V N <mugunthanvnm at ti.com> wrote:
>>> Add compatible for spansion 32MiB spi flash s25fl256s1.
>>>
>>> Signed-off-by: Mugunthan V N <mugunthanvnm at ti.com>
>>> ---
>>>  drivers/mtd/spi/sf_probe.c | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/mtd/spi/sf_probe.c b/drivers/mtd/spi/sf_probe.c
>>> index bc05d30..ffbce59 100644
>>> --- a/drivers/mtd/spi/sf_probe.c
>>> +++ b/drivers/mtd/spi/sf_probe.c
>>> @@ -515,6 +515,7 @@ static const struct dm_spi_flash_ops spi_flash_std_ops = {
>>>
>>>  static const struct udevice_id spi_flash_std_ids[] = {
>>>         { .compatible = "spi-flash" },
>>> +       { .compatible = "s25fl256s1" },
>>>         { }
>>
>> Never compare with spi-flash vs s25fl256s1 here former is driver
>> compatible string and later one is probed flash string name. we don't
>> need to add them in compatible list, better to add it on dts node
>> otherwise no issue the connected flash will detect while 'sf probe'
>>
>
> I agree that spi flash will be probed even without addition of compatibles.
>
> If there is no matching compatible between the dtb and driver,  the dt
> properties like spi-max-frequency, spi clock phase/polarity and spi
> bus-width are not parsed from DT as the of_offset of the spi device will
> be '-1'. This check and dt parse is done in spi_child_post_bind() in
> spi-uclass driver.
>
> Since spi bus-width is not read from DT, by default spi transfers are
> done in one wire mode and read throughput drops to 5.3Mbps. With Quad
> mode read throughput is 16.6Mbps in DRA74x EVM.
>

Why can't we try something like this [1] [2] I do agree with
documentation missing, may be we add add that well.

[1] arch/arm/dts/socfpga_cyclone5_sockit.dts
[2] arch/arm/dts/zynqmp-ep108.dts

> Adding spi-splash to DT is not possible now as it is not documented in
> Kernel binding documentation. Even if "spi-flash" compatible is added to
> u-boot DT then it will show diff when syncing the dts files from Kernel
> to U-boot and it has to be taken care for every sync. Tom Rini also has
> agreed to this [1].
>
> [1]: http://patchwork.ozlabs.org/patch/539780/
>

-- 
Jagan | openedev.