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

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Date:   Fri, 8 Mar 2019 10:20:19 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     Naga Sureshkumar Relli <nagasure@...inx.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "bbrezillon@...nel.org" <bbrezillon@...nel.org>
CC:     "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "marek.vasut@...il.com" <marek.vasut@...il.com>,
        "richard@....at" <richard@....at>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michal Simek <michals@...inx.com>,
        "nagasuresh12@...il.com" <nagasuresh12@...il.com>
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.

-- 
Regards
Vignesh