Re: [PATCH 4/4] spi: bcm-mspi: Add support to set serial baud clock rate

From: Mark Brown <broonie@kernel.org>
To: Florian Fainelli <f.fainelli@gmail.com>
Cc: Jonathan Richardson <jonathar@broadcom.com>,
	Dmitry Torokhov <dtor@google.com>,
	Anatol Pomazau <anatol@google.com>,
	Scott Branden <sbranden@broadcom.com>,
	Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Kumar Gala <galak@codeaurora.org>,
	linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org,
	bcm-kernel-feedback-list <bcm-kernel-feedback-list@broadcom.com>,
	devicetree@vger.kernel.org, Rafal Milecki <zajec5@gmail.com>,
	Brian Norris <computersforpeace@gmail.com>,
	Kevin Cernekee <cernekee@gmail.com>
Subject: Re: [PATCH 4/4] spi: bcm-mspi: Add support to set serial baud clock rate
Date: Mon, 6 Apr 2015 10:46:36 +0100	[thread overview]
Message-ID: <20150406094636.GC6023@sirena.org.uk> (raw)
In-Reply-To: <552037BB.7050803@gmail.com>

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On Sat, Apr 04, 2015 at 12:12:59PM -0700, Florian Fainelli wrote:
> Le 02/04/2015 12:23, Jonathan Richardson a écrit :

> > +		/* Calculate SPBR if clock-frequency provided. */
> > +		if (of_property_read_u32(dev->of_node, "clock-frequency",
> > +			&desired_rate) >= 0) {
> > +			u32 spbr = clk_get_rate(data->clk) / (2 * desired_rate);

> Usually, specifying a "clock-frequency" property is done when there is
> no clock provider available, yet we take this code path only if we could
> find a "mspi_clk" which sounds a litle weird.

> Once there is a proper "mspi_clk" clock, I would make it mandatory for
> the clock provider to be able to provide the rate as well?

As far as I can tell it's already mandatory if the property is present -
it's taking the clock presented to the block and then using an internal
divider to bring that down to the desired rate.

We are missing error handling though.

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