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Date: Tue, 4 Sep 2018 14:30:28 +0200
From: Boris Brezillon <boris.brezillon@bootlin.com>
To: Yogesh Narayan Gaur <yogeshnarayan.gaur@nxp.com>
Cc: "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
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Subject: Re: Query: spi-nor: dummy buswidth calculation
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+Macronix team

On Tue, 4 Sep 2018 09:28:11 +0000
Yogesh Narayan Gaur <yogeshnarayan.gaur@nxp.com> wrote:

> Hi Boris,
> 
> I have query regarding dummy bus width calculation for the read commands, added in the patch series [1]
> 
> In func m25p80_read(), dummy.buswidth is being assigned as
> +       op.dummy.buswidth = op.addr.buswidth;
> 
> Above, buswidth for dummy commands are being assigned and are marked equal to the buswidth of the address command.
> This is true for case when we are doing operation in 1-4-4 or 1-2-2 protocol where data as well as address are running on same data lines and having same buswidth.
> 
> I am adding support of octal commands in framework and for this needs to add support for 1-1-8 protocol for Micron flash MT35XU512ABA1G12.
> For octal command, 7Ch, flash is sending data and the dummy on the 8 data lines and address on 1 data line.

Interesting. Macronix is also working on octo-mode support. I think we
should sync instead of duplicating the work.

> 
> If I do below code change, then I am getting correct data else there is data corruption only in the first byte read.
> -       op.dummy.buswidth = op.addr.buswidth;
> +       op.dummy.buswidth = spi_nor_get_protocol_data_nbits(nor->read_proto);

Regarding this particular aspect, I just followed what was done before
the conversion to spi_mem_exec_op(). Maybe it was not correct though.

Regards,

Boris