linux-kernel - Re: [PATCH v2 3/4] clk: bcm2835: Add support for programming the audio domain clocks.

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Date:	Fri, 11 Sep 2015 12:08:21 +0200
From:	Martin Sperl <martin@...rl.org>
To:	Eric Anholt <eric@...olt.net>
Cc:	linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
	Mike Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	linux-kernel@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 3/4] clk: bcm2835: Add support for programming the audio domain clocks.


> On 10.09.2015, at 23:58, Eric Anholt <eric@...olt.net> wrote:
> 
> This adds support for enabling, disabling, and setting the rate of the
> audio domain clocks.  It will be necessary for setting the pixel clock
> for HDMI in the VC4 driver and let us write a cpufreq driver.  It will
> also improve compatibility with user changes to the firmware's
> config.txt, since our previous fixed clocks are unaware of it.
> 
> The firmware also has support for configuring the clocks through the
> mailbox channel, but the pixel clock setup by the firmware doesn't
> work, and it's Raspberry Pi specific anyway.  The only conflicts we
> should have with the firmware would be if we made firmware calls that
> result in clock management (like opening firmware V3D or ISP access,
> which we don't support in upstream), or on hardware over-thermal or
> under-voltage (when the firmware would rewrite PLLB to take the ARM
> out of overclock).  If that happens, our cached .recalc_rate() results
> would be incorrect, but that's no worse than our current state where
> we used fixed clocks.
> 
> The existing fixed clocks in the code are left in place to provide
> backwards compatibility with old device tree files.
> 
> Signed-off-by: Eric Anholt <eric@...olt.net>

This patch-sets sets the emmc clock to correct frequency - no longer
overclocking SDCards by a factor of 2.5.
This means booting from the eMMC on the Compute module works now
without issues.

Note that the DT bcm2835-rpi-b-plus.dtb can get used to boot
the compute module.

Thanks

Tested-by: Martin Sperl <kernel@...tin.sperl.org>

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