Message-ID: <552037BB.7050803@gmail.com>
Date: Sat, 04 Apr 2015 12:12:59 -0700
From: Florian Fainelli <f.fainelli@gmail.com>
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To: Jonathan Richardson <jonathar@broadcom.com>,
        Mark Brown <broonie@kernel.org>, Dmitry Torokhov <dtor@google.com>,
        Anatol Pomazau <anatol@google.com>
CC: 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
References: <1428002603-21892-1-git-send-email-jonathar@broadcom.com> <1428002603-21892-5-git-send-email-jonathar@broadcom.com>
In-Reply-To: <1428002603-21892-5-git-send-email-jonathar@broadcom.com>
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Le 02/04/2015 12:23, Jonathan Richardson a écrit :
> The driver wasn't setting the SPBR (serial clock baud rate) which caused
> it to run at the slowest speed possible. The driver now calculates the
> SPBR based on the reference clock frequency resulting in much faster
> SPI transfers.
> 
> Signed-off-by: Jonathan Richardson <jonathar@broadcom.com>
> ---

[snip]

> +	data->clk = devm_clk_get(dev, "mspi_clk");
> +	if (!IS_ERR(data->clk)) {
> +		int ret = clk_prepare_enable(data->clk);
> +
> +		if (ret < 0) {
> +			dev_err(dev, "failed to enable clock: %d\n", ret);
> +			return 0;
> +		}
> +
> +		/* 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?
--
Florian
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