linux-kernel - Re: [PATCH 3/3] arm: dts: bcm5301x: Add syscon based reboot in DT

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Message-ID: <20160105222605.GL31867@broadcom.com>
Date:	Tue, 5 Jan 2016 17:26:06 -0500
From:	Jon Mason <jonmason@...adcom.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	Florian Fainelli <f.fainelli@...il.com>,
	Hauke Mehrtens <hauke@...ke-m.de>,
	<bcm-kernel-feedback-list@...adcom.com>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH 3/3] arm: dts: bcm5301x: Add syscon based reboot in DT

On Fri, Dec 18, 2015 at 10:44:28PM +0100, Arnd Bergmann wrote:
> On Friday 18 December 2015 16:37:56 Jon Mason wrote:
> > +       cru: cru@...0c184 {
> > +               compatible = "syscon";
> > +               reg = <0x1800c184 0xc>;
> > +       };
> 
> It's unusual for a device to start at such an odd address. Are you sure
> it's not a larger device starting at 0x1800c000 or 0x18000000?

The CRU (Clock and Reset Unit) starts at 0x1800c100, with the
following layout:

CRU Clock Management at 0x1800c100-0x1800c180
CRU Reset at 0x1800c184
CRU Period Sample Clock at 0x1800c188
CRU Interrupt register at 0x1800c18c
CRU MDIO Control at 0x1800c190
CRU GPIO at 0x1800c1c0-0x1800c1e0
CRU SDIO 0x1800c200-0x1800c214
CRU RoboSW Interrupt at 0x1800c280
CRU Straps Control at 0x1800c2a0

The clock driver is already referencing the registers between
0x1800c100-0x1800c180, and the GPIO driver is referencing registers
between 0x1800c1c0-0x1800c1e0.

The reset part of the syscon seems to be the only useful thing in this
block.  Am I approaching this incorrectly?


> Also, please provide a more specific compatible string based on the
> name of the device in the data sheet. The node name in contrast should
> be more generic, e.g.
> 
> 	cru: system-controller@...0c000 {
> 		compatible = "brcm,bcm53010-cru", "syscon";

This is very similar between the NS and NSP (and NS2) platforms.  I'll
verify the layout and see if this can't be "brcm,iproc-cru" or
something similar.

Thanks,
Jon

> 		reg = <0x1800c000 0x400>; /* whatever the data sheet says */
> 	};
> 
> 
> 	Arnd
> 
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