linux-kernel - Re: [PATCH] mmc: pwrseq: Use highest priority for eMMC restart handler

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Message-ID: <5629227D.6060806@osg.samsung.com>
Date:	Thu, 22 Oct 2015 19:53:01 +0200
From:	Javier Martinez Canillas <javier@....samsung.com>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Markus Reichl <m.reichl@...etechno.de>,
	Anand Moon <linux.amoon@...il.com>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Alexandre Courbot <acourbot@...dia.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Heiko Stübner <heiko@...ech.de>
Subject: Re: [PATCH] mmc: pwrseq: Use highest priority for eMMC restart
 handler

Hello Doug,

On 10/22/2015 07:33 PM, Doug Anderson wrote:
> On Thu, Oct 22, 2015 at 9:07 AM, Javier Martinez Canillas

[snip]

>>
>> Do you know why the priority 200 was chosen for veyron gpi-restart ooi?
> 
> In David Riley's original patch the example had 200:
>     https://patchwork.kernel.org/patch/4784611/
> 
> In the ChromeOS 3.14 kernel tree I believe we're still using the old
> patch (we still have /bits/ 8).  ...it looks like I'm the one who
> originally added it to the veyron dts file and I set it to 200, so I'd
> presume that I just copied the example and called it "good enough".
>

I see, thanks for the explanation. I asked because I noticed that the
gpio-restart handler default priority was 129 and I didn't find other
restart handler used for this board with a prio > 129 so at least in
mainline, the priority 200 should not be necessary.

But now I see that it was indeed 128 but was bumped to 129 in commit:

bcd56fe1aa97 ("power: reset: gpio-restart: increase priority slightly")

which explains why the priority 200 was in the veyron DTS even when is
not needed anymore after that commit.
 
> I'm sure the upstream dts just used the number from the ChromeOS 3.14 tree...
> 
> Note that the GPIO-restart definitely need to be higher priorities
> than others in the system.  The two I know of off the top of my head
> are the "dw watchdog" and the one in the CRU.  The "dw watchdog" has a
> priority of 128 and so does the one in "rockchip/clk.c".  Hrm,
> actually, the Rockchip-specific one should probably have its priority
> bumped up since it seems better not to just randomly pick between
> these two...

Agreed about bumping the prio for the rockchip specific restart handler.

> 
> 
> -Doug
> --

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America
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