linux-kernel - Re: [ANNOUNCE] v5.2.9-rt3

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Date:   Tue, 20 Aug 2019 17:44:18 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Alexander Dahl <ada@...rsis.com>
Cc:     linux-rt-users@...r.kernel.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [ANNOUNCE] v5.2.9-rt3

Hi,

On 19/08/2019 13:03:51+0200, Alexander Dahl wrote:
> Hei hei,
> 
> just tried to compile this v5.2.9-rt3 for SAMA5D27-SOM1-EK1 based on 
> arch/arm/configs/sama5_defconfig and with running oldconfig and selecting 
> defaults, but that fails if CONFIG_ATMEL_TCB_CLKSRC_USE_SLOW_CLOCK is not set. 
> 
> I think this is due to changes for Atmel TCLIB in v5.2 and the not yet adapted 
> RT patch "clocksource: TCLIB: Allow higher clock rates for clock events", 
> right?

Patch clocksource-tclib-allow-higher-clockrates.patch needs to be
changed so:

ret = setup_clkevents(tc, best_divisor_idx);

becomes

ret = setup_clkevents(&tc, best_divisor_idx);

Also, I would think clocksource-tclib-add-proper-depend.patch could be
dropped. Instead, setup_clkevents should use atmel_tcb_divisors. It
would then be necessary to move its declaration before the function.

Sebastian, can you take care of that or do you expect a patch? In the
latter case, do you want a patch for the patch?

> 
> What's the recommended setting of this option for RT?
> 

Using the slow clock, will make the platform wakeup less frequently,
having a higher clock rate will give a better clockevent resolution.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com