linux-kernel - RE: [RFC PATCH 1/2] spi: Add support for Zynq QSPI controller

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Date:	Thu, 10 Jul 2014 09:44:44 +0000
From:	Punnaiah Choudary Kalluri <punnaiah.choudary.kalluri@...inx.com>
To:	Harini Katakam <harinikatakamlinux@...il.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>
CC:	Mark Brown <broonie@...nel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	"Mark Rutland" <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	linux-spi <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>,
	David Woodhouse <dwmw2@...radead.org>,
	"Brian Norris" <computersforpeace@...il.com>,
	Marek Vašut <marex@...x.de>,
	Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
	"Geert Uytterhoeven" <geert+renesas@...ux-m68k.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Jingoo Han <jg1.han@...sung.com>,
	Sourav Poddar <sourav.poddar@...com>,
	Michal Simek <michals@...inx.com>
Subject: RE: [RFC PATCH 1/2] spi: Add support for Zynq QSPI controller

HI Greet,

>-----Original Message-----
>From: Harini Katakam [mailto:harinikatakamlinux@...il.com]
>Sent: Thursday, July 10, 2014 3:01 PM
>To: Geert Uytterhoeven
>Cc: Mark Brown; Grant Likely; Rob Herring; Pawel Moll; Mark Rutland; Ian
>Campbell; Kumar Gala; linux-spi; linux-kernel@...r.kernel.org;
>devicetree@...r.kernel.org; linux-doc@...r.kernel.org; David Woodhouse;
>Brian Norris; Marek Vašut; Artem Bityutskiy; Geert Uytterhoeven; Sascha
>Hauer; Jingoo Han; Sourav Poddar; Michal Simek; Punnaiah Choudary Kalluri
>Subject: Re: [RFC PATCH 1/2] spi: Add support for Zynq QSPI controller
>
>Hi Geert,
>
>On Thu, Jul 10, 2014 at 2:48 PM, Geert Uytterhoeven
><geert@...ux-m68k.org> wrote:
>> Hi Harini,
>>
>> On Thu, Jul 10, 2014 at 10:50 AM, Harini Katakam <harinik@...inx.com>
>wrote:
>>> +       master->flags = SPI_MASTER_QUAD_MODE;
>>
>> SPI_MASTER_QUAD_MODE is not one of the SPI_MASTER_* defines
>> in include/linux/spi/spi.h?
>>
>
>I'm sorry about that. That flag is unused - will remove this statement.
>
>>> +       master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_RX_DUAL |
>SPI_RX_QUAD |
>>> +                           SPI_TX_DUAL | SPI_TX_QUAD;
>>
>> Your driver advertises Dual/Quad SPI Transfer capabilities, but it doesn't
>> check spi_transfer.[tr]x_nbits? How can it determine when to enable
>Dual/Quad?
>>
>
>Here the driver is just giving information that the controller support it.
>The MTD layer enables dual/quad based on what the flash supports; quad
>being the first priority
>I understand that the spi core reads rx, tx-bus-width property and
>master support flags and
>performs the necessary checks.

Just to add, the zynq qspi controller will automatically select the IO lines based
On the flash command. 

Regards,
Punnaiah

>
>Regards,
>Harini