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From: Maxime Ripard <maxime.ripard@bootlin.com>
To: Samuel Holland <samuel@sholland.org>
Cc: Chen-Yu Tsai <wens@csie.org>,
	Jassi Brar <jassisinghbrar@gmail.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>, Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Corentin Labbe <clabbe.montjoie@gmail.com>,
	Vasily Khoruzhick <anarsoul@gmail.com>,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-sunxi@googlegroups.com, linux-clk@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 04/10] mailbox: sunxi-msgbox: Add a new mailbox driver
Date: Wed, 21 Aug 2019 14:30:35 +0200
Message-ID: <20190821123035.tl4aakijjhw3bwbk@flea> (raw)
In-Reply-To: <bc09e14c-1cf5-8124-fc34-c651b78577ce@sholland.org>

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On Tue, Aug 20, 2019 at 08:07:53AM -0500, Samuel Holland wrote:
> On 8/20/19 6:18 AM, Ondřej Jirman wrote:
> >> +	reset = devm_reset_control_get(dev, NULL);
> >> +	if (IS_ERR(reset)) {
> >> +		ret = PTR_ERR(reset);
> >> +		dev_err(dev, "Failed to get reset control: %d\n", ret);
> >> +		goto err_disable_unprepare;
> >> +	}
> >> +
> >> +	ret = reset_control_deassert(reset);
> >> +	if (ret) {
> >> +		dev_err(dev, "Failed to deassert reset: %d\n", ret);
> >> +		goto err_disable_unprepare;
> >> +	}
> >
> > You need to assert the reset again from now on, in error paths. devm
> > will not do that for you.
>
> I know, and that's intentional. This same message box device is used for ATF to
> communicate with SCP firmware (on a different channel). This could be happening
> on a different core while Linux is running. So Linux is not allowed to deassert
> the reset. clk_disable_unprepare() is only okay because the clock is marked as
> critical.

I agree with Ondrej that since this is clearly not the standard use of
the API, this must have a big comment explaining why we're doing it
this way.

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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  parent reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-20  3:23 [PATCH v4 00/10] Allwinner sunxi message box support Samuel Holland
2019-08-20  3:23 ` [PATCH v4 01/10] clk: sunxi-ng: Mark msgbox clocks as critical Samuel Holland
2019-08-20  3:23 ` [PATCH v4 02/10] clk: sunxi-ng: Mark AR100 " Samuel Holland
2019-08-20  7:11   ` Maxime Ripard
2019-08-20 13:02     ` Samuel Holland
2019-08-21 12:24       ` Maxime Ripard
2019-09-05 18:56         ` Stephen Boyd
2019-08-20  3:23 ` [PATCH v4 03/10] dt-bindings: mailbox: Add a sunxi message box binding Samuel Holland
2019-08-20  7:14   ` Maxime Ripard
2019-08-20 13:04     ` Samuel Holland
2019-08-21 12:07       ` Maxime Ripard
2019-08-20  3:23 ` [PATCH v4 04/10] mailbox: sunxi-msgbox: Add a new mailbox driver Samuel Holland
2019-08-20  8:27   ` Maxime Ripard
2019-08-20 11:18   ` Ondřej Jirman
2019-08-20 13:07     ` Samuel Holland
2019-08-20 13:34       ` Ondřej Jirman
2019-08-21 12:30       ` Maxime Ripard [this message]
2019-08-20  3:23 ` [PATCH v4 05/10] ARM: dts: sunxi: a80: Add msgbox node Samuel Holland
2019-08-20  8:15   ` Maxime Ripard
2019-08-20 13:17     ` Samuel Holland
2019-08-23 14:56       ` Maxime Ripard
2019-08-20  3:23 ` [PATCH v4 06/10] ARM: dts: sunxi: a83t: " Samuel Holland
2019-08-20  3:23 ` [PATCH v4 07/10] ARM: dts: sunxi: h3/h5: " Samuel Holland
2019-08-20  3:23 ` [PATCH v4 08/10] arm64: dts: allwinner: a64: " Samuel Holland
2019-08-20  3:23 ` [PATCH v4 09/10] arm64: dts: allwinner: h6: " Samuel Holland
2019-08-20  3:23 ` [PATCH v4 10/10] [DO NOT MERGE] drivers: firmware: msgbox demo Samuel Holland
2019-09-09  3:22 ` [PATCH v4 00/10] Allwinner sunxi message box support Ondřej Jirman
2019-09-09  3:54   ` Samuel Holland
2019-09-09 12:36     ` Ondřej Jirman

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