On Tue, Oct 18, 2016 at 10:03 PM, Albert ARIBAUD
<albert.aribaud@xxxxxxxx> wrote:
> Le Mon, 3 Oct 2016 21:57:58 +0200, Geert Uytterhoeven
> <geert@xxxxxxxxxxxxxx> a écrit :
>
>> On Mon, Oct 3, 2016 at 8:51 PM, Rob Herring <robh@xxxxxxxxxx> wrote:
>> > On Tue, Sep 27, 2016 at 07:59:57AM +0200, Albert ARIBAUD (3ADEV) wrote:
>> >> Introduce spi-bus-width property for bus subnodes, to
>> >> specify per-bus capability to use NORMAL, FAST, DUAL,
>> >> and/or QUAD reads.
>> >>
>> >> Signed-off-by: Albert ARIBAUD (3ADEV) <albert.aribaud@xxxxxxxx>
>> >> ---
>> >> Documentation/devicetree/bindings/mtd/fsl-quadspi.txt | 18 ++++++++++++++++++
>> >> 1 file changed, 18 insertions(+)
>> >
>> > Make this a common property.
>
> @Rob: do you mean common to all slaves, i.e. described
> in ./Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt?
>
>> They already exist:
>>
>> Documentation/devicetree/bindings/spi/spi-bus.txt:
>> - spi-tx-bus-width - (optional) The bus width (number of data wires)
>> that is used for MOSI. Defaults to 1 if not present.
>> - spi-rx-bus-width - (optional) The bus width (number of data wires)
>> that is used for MISO. Defaults to 1 if not present.
>>
>> The above are for normal/dual/quad.
>>
>> "Fast" is not a property of the bus, but of the SPI slave, right? Cfr.
>>
>> Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt:
>> - m25p,fast-read : Use the "fast read" opcode to read data from the
>> chip instead of the usual "read" opcode. This opcode is not supported
>> by all chips and support for it can not be detected at runtime.
>> Refer to your chips' datasheet to check if this is
>> supported by your chip.
>>
>> Gr{oetje,eeting}s,
>
> @Geert: the problem here is that on the board for which I wrote this
> patch, only one of the two NOR slaves can do quad SPI; the other one
> can do dual at best. Setting a bus property would prevent the
> quad-capable device from doing actual quad reads.
>
> The fsl-quadspi driver already supports per-NOR read and erase commands
> to support heterogeneous NOR setups. A per-NOR bus width property would
> make sense in this light.
spi-[tx]x-bus-width is already a property for the SPI slave, not for
the whole bus.
So you can use 4 for the quad-capable device, and 1 or 2 for the other.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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