Re: [RFC PATCH 1/2] spi: Add support for Zynq QSPI controller

From: Harini Katakam
Date: Thu Jul 10 2014 - 08:40:01 EST

Hi Mark,

On Thu, Jul 10, 2014 at 5:31 PM, Mark Brown <broonie@xxxxxxxxxx> wrote:
> On Thu, Jul 10, 2014 at 04:03:19PM +0530, Harini Katakam wrote:
>> OK. Correct me if I'm wrong but announcing this support in master->flags is
>> just to say the controller supports it - Like Punnaiah mentioned in the other
> No, it's broken to set this if there is no ability to use it.
>> mail, nothing specific needs to be done from the controller driver to enable
>> dual/quad support. This is at the SOC/IP level.
> How does the client driver select the width to use for a transfer?

This controller is meant to be used only with flash devices.
The flash devices' supported width will be reflected in a table in MTD layer.
When selecting, priority is given to quad over dual and single in the MTD and
it will send commands using the supported tx/rx bus width accordingly.
About the supported bus width on board, tx-bus-width and rx-bus-width
properties in dts will have the info; which I believe spi core uses.

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