linux-kernel - Re: [PATCH 0/4] cpufreq support for the Raspberry Pi

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Date:   Wed, 05 Jun 2019 14:27:26 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Stefan Wahren <wahrenst@....net>,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org
Cc:     f.fainelli@...il.com, ptesarik@...e.com, sboyd@...nel.org,
        viresh.kumar@...aro.org, mturquette@...libre.com,
        rjw@...ysocki.net, linux-kernel@...r.kernel.org, eric@...olt.net,
        bcm-kernel-feedback-list@...adcom.com, linux-clk@...r.kernel.org,
        mbrugger@...e.de, ssuloev@...altech.com
Subject: Re: [PATCH 0/4] cpufreq support for the Raspberry Pi

Hi Stefan,

On Wed, 2019-06-05 at 13:34 +0200, Stefan Wahren wrote:
> Hi,
> 
> Am 05.06.19 um 13:00 schrieb Nicolas Saenz Julienne:
> > Hi Stefan,
> > thanks for the review, I took note of your code comments.
> > 
> > On Wed, 2019-06-05 at 11:46 +0200, Stefan Wahren wrote:
> > > Hi Nicolas,
> > > 
> > > Am 04.06.19 um 19:32 schrieb Nicolas Saenz Julienne:
> > > > Hi all,
> > > > this series aims at adding cpufreq support to the Raspberry Pi family of
> > > > boards.
> > > > 
> > > > The previous revision can be found at: 
> > > > https://lkml.org/lkml/2019/5/20/431
> > > > 
> > > > The series first factors out 'pllb' from clk-bcm2385 and creates a new
> > > > clk driver that operates it over RPi's firmware interface[1]. We are
> > > > forced to do so as the firmware 'owns' the pll and we're not allowed to
> > > > change through the register interface directly as we might race with the
> > > > over-temperature and under-voltage protections provided by the firmware.
> > > it would be nice to preserve such design decision in the driver as a
> > > comment, because the cover letter usually get lost.
> > > > Next it creates a minimal cpufreq driver that populates the CPU's opp
> > > > table, and registers cpufreq-dt. Which is needed as the firmware
> > > > controls the max and min frequencies available.
> > > I tested your series on top of Linux 5.2-rc1 with multi_v7_defconfig and
> > > manually enable this drivers. During boot with Raspbian rootfs i'm
> > > getting the following:
> > > 
> > > [    1.177009] cpu cpu0: failed to get clock: -2
> > > [    1.183643] cpufreq-dt: probe of cpufreq-dt failed with error -2
> > This is surprising, who could be creating a platform_device for cpufreq-dt
> > apart from raspberrypi-cpufreq? Just to make things clear, you're using the
> > device tree from v5.2-rc1 (as opposed to the Raspbian one)?
> 
> sorry my fault, i thought it already has been replaced. The behavior in
> this unexpected case is fine, since it doesn't crash.
> 
> I replaced the the DTB with the mainline one, but now i'm getting this:
> 
> [    4.566068] cpufreq: cpufreq_online: CPU0: Running at unlisted freq:
> 600000 KHz
> [    4.580690] cpu cpu0: dev_pm_opp_set_rate: Invalid target frequency 0
> [    4.594391] cpufreq: __target_index: Failed to change cpu frequency: -22

Ok, this looks more more like my fault, probably an overflow error somewhere. I
saw something similar while testing it on RPI2b. Which board & config was this
run with? Could you confirm the clk-raspberrypi.c message verifying the max and
min frequencies showed up and was correct.

Regards,
Nicolas


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