linux-kernel - Re: [PATCH 2/2] SPI: Add support for Zynq Quad SPI controller

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Date:	Fri, 4 Apr 2014 17:56:47 +0530
From:	Harini Katakam <harinikatakamlinux@...il.com>
To:	Mark Brown <broonie@...nel.org>
Cc:	Punnaiah Choudary Kalluri <punnaiah.choudary.kalluri@...inx.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>, linux-spi@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Michal Simek <michal.simek@...inx.com>,
	Punnaiah Choudary <kpc528@...il.com>,
	punnaiah choudary kalluri <kalluripunnaiahchoudary@...il.com>,
	Punnaiah Choudary Kalluri <punnaia@...inx.com>
Subject: Re: [PATCH 2/2] SPI: Add support for Zynq Quad SPI controller

Hi Mark,

On Fri, Apr 4, 2014 at 4:38 PM, Mark Brown <broonie@...nel.org> wrote:
> On Fri, Apr 04, 2014 at 08:59:47AM +0530, Harini Katakam wrote:
>> On Fri, Apr 4, 2014 at 2:59 AM, Mark Brown <broonie@...nel.org> wrote:
>
>> > Why would a transfer be being set up without a transfer being provided?
>
>> The setup function calls this function before a transfer is initiated.
>> In this case NULL is passed to setup_transfer (see below) and
>> SPI is initialized with default clock configuration.
>> This initialization is necessary because otherwise this clock config
>> would be done
>> only after SPI is enabled in prepare_hardware, which is wrong.
>> (I'm checking for master->busy in setup to address your previous
>> comment on SPI).
>
> The requirement for setup() to work when other transfers are in progress
> is clear and unambiguous, it really isn't acceptable to reconfigure
> hardware in use by a runing transfer in setup().
>

OK. I'll remove setup_transfer here and handle clock configuration elsewhere.

>> I explained the same in SPI v2 changes and this valid there too.
>
> This is v2?
>

No. This "Zynq QSPI" patch is v1.
I was referring to "Cadence SPI" v2 patch in which you pointed to these
comments.

Sorry for the confusion.

<snip>

>> >> +static int __maybe_unused zynq_qspi_suspend(struct device *_dev)
>> >> +{
>> >> +     struct platform_device *pdev = container_of(_dev,
>> >> +                     struct platform_device, dev);
>> >> +     struct spi_master *master = platform_get_drvdata(pdev);
>> >> +
>> >> +     spi_master_suspend(master);
>> >> +
>> >> +     zynq_unprepare_transfer_hardware(master);
>
>> > Why are you unpreparing the hardware - the framework should be doing
>> > that for you if the device is active, if it's not you've got an extra
>> > clock disable here?
>
>> I called unprepare_hardware  becuase it does the things necessary
>> after master suspend - disable clock and controller.
>> (I thought this was your suggestion for SPI?)
>
> Why are these things required after the core has already idled the
> device (using exactly the same function)?

Ok. It's unecessary I'll remove it.

Regards,
Harini
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