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Date:   Fri, 12 Apr 2019 12:06:45 +0200
From:   Heiko Stübner <heiko@...ech.de>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Elaine Zhang <zhangqing@...k-chips.com>, dbasehore@...omium.org,
        amstan@...omium.org, linux-rockchip@...ts.infradead.org,
        briannorris@...omium.org, mka@...omium.org, ryandcase@...omium.org,
        Chris Zhong <zyw@...k-chips.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/5] clk: rockchip: Turn on "aclk_dmac1" for suspend

Am Freitag, 12. April 2019, 01:21:53 CEST schrieb Douglas Anderson:
> Experimentally it can be seen that going into deep sleep (specifically
> setting PMU_CLR_DMA and PMU_CLR_BUS in RK3288_PMU_PWRMODE_CON1)
> appears to fail unless "aclk_dmac1" is on.  The failure is that the
> system never signals that it made it into suspend on the GLOBAL_PWROFF
> pin and it just hangs.
> 
> NOTE that it's confirmed that it's the actual suspend that fails, not
> one of the earlier calls to read/write registers.  Specifically if you
> comment out the "PMU_GLOBAL_INT_DISABLE" setting in
> rk3288_slp_mode_set() and then comment out the "cpu_do_idle()" call in
> rockchip_lpmode_enter() then you can exercise the whole suspend path
> without any crashing.
> 
> This is currently not a problem with suspend upstream because there is
> no current way to exercise the deep suspend code.  However, anyone
> trying to make it work will run into this issue.
> 
> This was not a problem on shipping rk3288-based Chromebooks because
> those devices all ran on an old kernel based on 3.14.  On that kernel
> "aclk_dmac1" appears to be left on all the time.
> 
> There are several ways to skin this problem.
> 
> A) We could add "aclk_dmac1" to the list of critical clocks and that
> apperas to work, but presumably that wastes power.
> 
> B) We could keep a list of "struct clk" objects to enable at suspend
> time in clk-rk3288.c and use the standard clock APIs.
> 
> C) We could make the rk3288-pmu driver keep a list of clocks to enable
> at suspend time.  Presumably this would require a dts and bindings
> change.
> 
> D) We could just whack the clock on in the existing syscore suspend
> function where we whack a bunch of other clocks.  This is particularly
> easy because we know for sure that the clock's only parent
> ("aclk_cpu") is a critical clock so we don't need to do anything more
> than ungate it.
> 
> In this case I have chosen D) because it seemed like the least work,
> but any of the other options would presumably also work fine.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

applied for 5.2 with Elaine's rb

Thanks
Heiko


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