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

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Date:   Tue, 12 Mar 2019 22:36:43 +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

Hi,

On 11/03/19 10:02 AM, Naga Sureshkumar Relli wrote:
> Hi Vignesh,
> 
>> -----Original Message-----
>> From: linux-spi-owner@...r.kernel.org <linux-spi-owner@...r.kernel.org> On Behalf Of
>> Vignesh Raghavendra
>> Sent: Friday, March 8, 2019 10:20 AM
>> To: Naga Sureshkumar Relli <nagasure@...inx.com>; broonie@...nel.org;
>> bbrezillon@...nel.org
>> Cc: linux-spi@...r.kernel.org; dwmw2@...radead.org; marek.vasut@...il.com;
>> richard@....at; linux-mtd@...ts.infradead.org; linux-kernel@...r.kernel.org; Michal Simek
>> <michals@...inx.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.
> Thanks.
> Shall I wait for others to review or go ahead by addressing your previous comments?
> 

Typically, for a new driver, I would wait at least 2 weeks from date of
posting so that other reviewers have sufficient time to look into the patch.


-- 
Regards
Vignesh