linux-kernel - Re: [PATCH 2/2] spi: bcm-mspi: Add support for Broadcom MSPI driver.

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Message-ID: <20150514190823.GR2761@sirena.org.uk>
Date:	Thu, 14 May 2015 20:08:23 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Scott Branden <sbranden@...adcom.com>
Cc:	Jonathan Richardson <jonathar@...adcom.com>,
	Dmitry Torokhov <dtor@...gle.com>,
	Anatol Pomazau <anatol@...gle.com>,
	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-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
	bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
	devicetree@...r.kernel.org
Subject: Re: [PATCH 2/2] spi: bcm-mspi: Add support for Broadcom MSPI driver.

On Thu, May 14, 2015 at 11:19:01AM -0700, Scott Branden wrote:
> On 15-05-14 03:31 AM, Mark Brown wrote:

> >Chip vendors often say this sort of thing and then get surprised by what
> >their users choose to do, and even if it only ever gets used with flash
> >all it would take is some new flash command which can use full duplex
> >for something.  Please write the code so it at least tries to handle
> >full duplex operation, if you can't test it fully that's not the end of
> >the world.  It doesn't look like it should be particularly difficult.

> Yes, there is always room for improvements in code.  In this case - it
> really is not worth our time to add code we can't test.  We try to deliver
> code that we can test and actually works.  Yes, if anyone needs to use the

While I try to not apply code that has obvious problems with silent data
corruption in it which is what we have just now.

> mspi for full duplex operation code can be added in the future - it is
> software.  This block has gone through many generations of our SoCs and has
> only been used for this purpose - the bootROM boots from this SPI only.  It
> is dedicated for this purpose.

All it takes is one hardware engineer who sees a SPI controller and a
GPIO they can use for chip select; I wouldn't be so sure that nobody
ever fixed this up locally (or happened to use a device that only needed
single duplex).

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