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From: Paul Walmsley <paul@pwsan.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org, linux-pm@vger.kernel.org,
	Anup Patel <anup@brainfault.org>,
	Sebastian Reichel <sre@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	linux-riscv <linux-riscv@lists.infradead.org>
Subject: Re: QEMU RISC-V virt machine poweroff driver
Date: Mon, 11 Nov 2019 17:20:41 +0000 (UTC)
Message-ID: <alpine.DEB.2.21.999.1911111717320.32333@utopia.booyaka.com> (raw)
In-Reply-To: <20191111161217.GA19157@lst.de>

On Mon, 11 Nov 2019, Christoph Hellwig wrote:

> On Mon, Nov 11, 2019 at 05:06:24PM +0530, Anup Patel wrote:
> > We really don't need this driver. Instead, we can simply re-use
> > following drivers:
> > mfd/syscon
> > power/reset/syscon-reboot
> > power/reset/syscon-poweroff
> > 
> > Just enable following to your defconfig:
> > CONFIG_POWER_RESET=y
> > CONFIG_POWER_RESET_SYSCON=y
> > CONFIG_POWER_RESET_SYSCON_POWEROFF=y
> > CONFIG_SYSCON_REBOOT_MODE=y
> > 
> > 
> > Once above drivers are enabled in your defconfig, make sure
> > test device DT nodes are described in the following way for virt machine:
> 
> Oh well, that is a lot more churn than a just works driver, and
> will also pull it dependencies like regmap which quite blow up the
> kernel size.  But I guess that is where modern Linux drivers are
> heading, so I'm not going to complain too loud..

The core issue is that putting random register writes in DT doesn't match 
the hardware.  And the doctrine with DT has always been that it's supposed 
to represent the actual hardware.  On FPGA bitstreams or ASICs that have 
the teststatus/testfinisher IP block, there really is an IP block out 
there - it's not just a bare register.

If you update your driver to note that this is a SiFive IP block rather 
than a "RISC-V" IP block, I'll ack it.


- Paul

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Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-07 21:24 Christoph Hellwig
2019-11-07 21:24 ` [PATCH 1/2] dt-bindings: power: reset: document the QEMU RISC-V virt machine poweroff device Christoph Hellwig
2019-11-07 21:52   ` Palmer Dabbelt
2019-11-07 22:32   ` Paul Walmsley
2019-11-14  1:44     ` Rob Herring
2019-11-07 21:24 ` [PATCH 2/2] power: reset: add a QEMU RISC-V virt machine poweroff driver Christoph Hellwig
2019-11-07 21:53   ` Palmer Dabbelt
2019-11-07 22:33   ` Paul Walmsley
2019-11-07 21:56 ` Palmer Dabbelt
2019-11-11 11:36 ` Anup Patel
2019-11-11 16:12   ` Christoph Hellwig
2019-11-11 17:20     ` Paul Walmsley [this message]
2019-11-12  4:16       ` Anup Patel
2019-11-14  1:50         ` Rob Herring
2019-11-15 22:14 ` Nick Kossifidis
2019-11-18  6:12   ` Anup Patel

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