From: Cyrille Pitchen <cyrille.pitchen@atmel.com>
To: Mark Brown <broonie@kernel.org>
Cc: <nicolas.ferre@atmel.com>, <linux-spi@vger.kernel.org>,
<linux-kernel@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<devicetree@vger.kernel.org>, <robh+dt@kernel.org>,
<pawel.moll@arm.com>, <mark.rutland@arm.com>,
<ijc+devicetree@hellion.org.uk>, <galak@codeaurora.org>
Subject: Re: [PATCH v3 2/3] spi: atmel: update DT bindings documentation
Date: Thu, 11 Jun 2015 18:37:51 +0200 [thread overview]
Message-ID: <5579B95F.9060307@atmel.com> (raw)
In-Reply-To: <20150609172531.GM14071@sirena.org.uk>
Le 09/06/2015 19:25, Mark Brown a écrit :
> On Tue, Jun 09, 2015 at 01:53:53PM +0200, Cyrille Pitchen wrote:
>> - add new property "atmel,fifo-size"
>
> Why is this a property and not something we know from the IP version?
>
Hi Mark,
Please be aware that the VERSION register can not be used to guess the
size of FIFOs. Indeed, for a given hardware version, the SPI controller
can be integrated on Atmel SoCs with different FIFO sizes. Also the
"atmel,fifo-size" property is optional as older SPI controllers don't
embed FIFO at all.
Besides, the FIFO size can not be read or guessed from other registers:
When designing the FIFO feature, no dedicated registers were added to
store this size. Unused spaces in the I/O register range are limited and
better reserved for future usages. Instead, the FIFO size of each
peripheral is documented in the programmer datasheet.
Finally, on a given SoC, there can be several instances of the SPI
controller with different FIFO sizes. This explain why we'd rather use a
dedicated DT property than use the "compatible" property.
I hope these pieces of information will help to clarify this point.
Of course, we are open to other suggestions.
Best Regards,
Cyrille
next prev parent reply other threads:[~2015-06-11 16:37 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-09 11:53 [PATCH v3 0/3] spi: atmel: add support to FIFOs and the internal chip-select Cyrille Pitchen
2015-06-09 11:53 ` [PATCH v3 1/3] spi: atmel: add support for the internal chip-select of the spi controller Cyrille Pitchen
2015-06-09 12:15 ` Nicolas Ferre
2015-06-09 17:26 ` Mark Brown
2016-01-05 21:50 ` Måns Rullgård
2016-01-07 15:40 ` Mark Brown
2016-01-07 16:14 ` Måns Rullgård
2016-01-27 15:46 ` Nicolas Ferre
2016-01-27 15:53 ` Måns Rullgård
2016-01-27 16:55 ` Nicolas Ferre
2016-01-27 16:57 ` Måns Rullgård
2015-06-09 11:53 ` [PATCH v3 2/3] spi: atmel: update DT bindings documentation Cyrille Pitchen
2015-06-09 12:15 ` Nicolas Ferre
2015-06-09 17:25 ` Mark Brown
2015-06-11 16:37 ` Cyrille Pitchen [this message]
2015-06-15 15:49 ` Mark Brown
2015-06-09 11:53 ` [PATCH v3 3/3] spi: atmel: add support to FIFOs Cyrille Pitchen
2015-06-09 12:24 ` Nicolas Ferre
2015-06-09 17:30 ` Mark Brown
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