Re: [PATCH 1/5] clk: rockchip: Turn on "aclk_dmac1" for suspend

From: "Heiko Stübner" <heiko@sntech.de>
To: Douglas Anderson <dianders@chromium.org>
Cc: Elaine Zhang <zhangqing@rock-chips.com>,
	dbasehore@chromium.org, amstan@chromium.org,
	linux-rockchip@lists.infradead.org, briannorris@chromium.org,
	mka@chromium.org, ryandcase@chromium.org,
	Chris Zhong <zyw@rock-chips.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>,
	linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/5] clk: rockchip: Turn on "aclk_dmac1" for suspend
Date: Fri, 12 Apr 2019 12:06:45 +0200	[thread overview]
Message-ID: <17495106.TRDjcDkMKC@diego> (raw)
In-Reply-To: <20190411232157.55125-1-dianders@chromium.org>

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@chromium.org>

applied for 5.2 with Elaine's rb

Thanks
Heiko