linux-kernel - Re: [PATCH] clk: rockchip: add pclk_vio

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Message-ID: <6790996.3s1cEPUy90@diego>
Date:	Tue, 14 Jun 2016 08:43:09 +0200
From:	Heiko Stübner <heiko@...ech.de>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Xing Zheng <zhengxing@...k-chips.com>,
	elaine zhang <elaine.zhang@...k-chips.com>,
	Tao Huang <huangtao@...k-chips.com>,
	Brian Norris <briannorris@...omium.org>,
	Yakir Yang <ykk@...k-chips.com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	linux-clk <linux-clk@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] clk: rockchip: add pclk_vio_grf to critical clock on the RK3399

Am Montag, 13. Juni 2016, 20:49:39 schrieb Doug Anderson:
> Hi,
> 
> On Mon, Jun 13, 2016 at 8:02 PM, Xing Zheng <zhengxing@...k-chips.com> 
wrote:
> > Hi Doug,
> > 
> > On 2016年06月14日 07:46, Doug Anderson wrote:
> >> Even if it's not much power, it seems like we should still turn it off
> >> and on in the right place.  Unless I'm mistaken it should be such a
> >> simple patch provide the clock to the right driver and then get the
> >> clock when appropriate.
> > 
> > Yes, I talked with Yakir and we intent to enable/disable the pclk_vio_grf
> > in video drivers,
> > so this patch will be dropped.
> > 
> >>> I will refer the latest TRM to update a new patch for always enable
> >>> these
> >>> GRFs.
> >> 
> >> Does that mean you're going to make these all critical clocks?  That
> >> doesn't sound so great...
> >> 
> >> -Doug
> > 
> > Maybe, I heard that they are removed in the updated TRM, but I have not
> > got
> > the TRM yet.
> > I will double check it, and it seems that you do not agree to remove these
> > clock...
> 
> Well, if it were to be removed from the TRM then that would be a
> strong sign that the SoC designers think that this clock should never
> ever be turned off.  If that were the case I don't think I could
> object to leaving this clock on all the time.  Presumably then we'd
> totally remove the clock from the clock tree and rely on firmware to
> leave it on?  Technically removing this clock is not really
> device-tree backward compatible, but I guess if there are no current
> users...
> 
> ...note: if the clock IS listed in the TRM and there's ever a chance
> that we'd want to turn it off, it's much easier to set that up all
> now.  Trying to later go in and decide that these clocks are no longer
> "always on" gets into all sorts of weird device tree backward
> compatibility corner cases.

PCLK_VIO_GRF gets already exported as clock-id, so we already have the wired 
corner-case :-) . But we'll see how this plays out.