Re: [PATCH 2/2] fsl-quadspi: introduce per-bus spi-bus-width property

Hi Rob and Geert,

Le Mon, 3 Oct 2016 21:57:58 +0200, Geert Uytterhoeven
[off-list ref] a écrit :

On Mon, Oct 3, 2016 at 8:51 PM, Rob Herring [off-list ref] wrote:

quoted

On Tue, Sep 27, 2016 at 07:59:57AM +0200, Albert ARIBAUD (3ADEV) wrote:  

quoted

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) <redacted>
---
 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.

Cordialement,
Albert ARIBAUD
3ADEV
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