linux-kernel - Re: [PATCH] soc: rockchip: power-domain: Don't (incorrectly) set rk3399 up/down counts

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Date:   Mon, 26 Sep 2016 22:18:42 +0200
From:   Heiko Stuebner <heiko@...ech.de>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     linux-rockchip@...ts.infradead.org, zhangqing@...k-chips.com,
        wxt@...k-chips.com, zhengxing@...k-chips.com,
        dbasehore@...omium.org, shawn.lin@...k-chips.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] soc: rockchip: power-domain: Don't (incorrectly) set rk3399 up/down counts

Am Donnerstag, 18. August 2016, 11:56:01 CEST schrieb Douglas Anderson:
> On rk3288 it was important that powerdown and powerup counts for the
> CPU/GPU in the kernel because:
> * The power on default was crazy long.
> * We couldn't rely on the firmware to set this up because really this
>   wasn't the firmware's job--the kernel was the only one that really
>   cared about bringing up / down CPUs and the GPU and doing suspend /
>   resume (which involves bringing up / down CPUs).
> 
> On newer ARM systems (like rk3399) ARM Trusted Firmware is in charge of
> bringing up and down the CPUs and it really should be in charge of
> setting all these counts right.  After all ATF is in charge of suspend /
> resume and CPU up / down.  Let's get out of the way and let ATF do its
> job.
> 
> A few other motivations for doing this:
> * Depending on another configuration (PMU_24M_EN_CFG) these counts can
>   be either in 24M or 32k cycles.  Thus, though ATF isn't really so
>   involved in bringing up the GPU, ATF should probably manage the counts
>   for everything so it can also manage the 24M / 32k choice.
> * It turns out that (right now) 24M mode is broken on rk3399 and not
>   being used.  That means that the count the kernel was programming
>   in (24) was not 1 us (which it seems was intended) but was actually
>   .75 ms
> * On rk3399 there are actually 2 separate registers for setting CPU
>   up/down time plus 1 register for GPU up/down time.  The curent kernel
>   code actually was putting the register for the "little" cores in the
>   "CPU" slot and the register for the "big" cores in the "GPU" slot.  It
>   was never initting the GPU counts.
> 
> Note: this change assumes that ATF will actually set these values at
> boot, as I'm proposing in <http://crosreview.com/372381>.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

applied to my drivers branch for 4.10


Thanks
Heiko