RE: [RFC PATCH 2/2] spi: spi-mem: Add support for Zynq QSPI controller

[Naga Sureshkumar Relli <nagasure@xxxxxxxxxx>]

Hi Vignesh,

> -----Original Message-----
> From: linux-spi-owner@xxxxxxxxxxxxxxx <linux-spi-owner@xxxxxxxxxxxxxxx> On Behalf Of
> Vignesh Raghavendra
> Sent: Friday, March 8, 2019 10:20 AM
> To: Naga Sureshkumar Relli <nagasure@xxxxxxxxxx>; broonie@xxxxxxxxxx;
> bbrezillon@xxxxxxxxxx
> Cc: linux-spi@xxxxxxxxxxxxxxx; dwmw2@xxxxxxxxxxxxx; marek.vasut@xxxxxxxxx;
> richard@xxxxxx; linux-mtd@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Michal Simek
> <michals@xxxxxxxxxx>; nagasuresh12@xxxxxxxxx
> Subject: Re: [RFC PATCH 2/2] spi: spi-mem: Add support for Zynq QSPI controller
> 
> 
> 
> On 01/03/19 4:32 PM, Naga Sureshkumar Relli wrote:
> >>> +static bool zynq_qspi_supports_op(struct spi_mem *mem,
> >>> +				  const struct spi_mem_op *op)
> >>> +{
> >>> +	int ret;
> >>> +
> >>> +	ret = zynq_qspi_check_buswidth(op->cmd.buswidth);
> >>> +
> >>> +	if (op->addr.nbytes)
> >>> +		ret |= zynq_qspi_check_buswidth(op->addr.buswidth);
> >>> +
> >>> +	if (op->dummy.nbytes)
> >>> +		ret |= zynq_qspi_check_buswidth(op->dummy.buswidth);
> >>> +
> >>> +	if (op->data.nbytes)
> >>> +		ret |= zynq_qspi_check_buswidth(op->data.buswidth);
> >>> +
> >>> +	if (ret)
> >>> +		return false;
> >>> +
> >> spi_mem_default_supports_op() already has this code.
> >> Could you change, spi_mem_supports_op() to call
> >> spi_mem_default_supports_op() first before controller specific
> >> ->supports_op()? So that, above code can be dropped.
> > Ok, I will update it.
> >>> +	/*
> >>> +	 * The number of address bytes should be equal to or less than 3 bytes.
> >>> +	 */
> >>> +	if (op->addr.nbytes > 3)
> >>> +		return false;
> >>> +
> >> Hmm, how does the driver handle flash devices >16MB in size? Not supported?
> > Zynq QSPI controller doesn't support 4 byte addressing.
> > So to support > 16MB size, we have to use EAR(extended address register).
> > As it is initial version of driver, I haven't added this code. This needs to be added in spi-nor.c.
> > Previously I have sent an RFC patch to support all these.
> > But Boris suggested to upstream the basic one first under spi-mem frame work.
> > Not only this support, there are other features like dual parallel and dual stacked.
> > All these features require additional support from spi-nor framework.
> > We have another QSPI controller on ZynqMP SOC, which is also similar(but it supports
> 4Byte addressing).
> > So by consolidating all these, I sent this patch.
> >
> > Please let me know your suggestion on this.
> 
> Sounds fine to me. Support for > 16MB flash using EAR can come later.
Thanks.
Shall I wait for others to review or go ahead by addressing your previous comments?

Thanks,
Naga Sureshkumar Relli
> 
> --
> Regards
> Vignesh
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