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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Mikko Perttunen' <mperttunen@nvidia.com>,
        "ldewangan@nvidia.com" <ldewangan@nvidia.com>,
        "digetx@gmail.com" <digetx@gmail.com>,
        "thierry.reding@gmail.com" <thierry.reding@gmail.com>,
        "jonathanh@nvidia.com" <jonathanh@nvidia.com>,
        "wsa@kernel.org" <wsa@kernel.org>
CC:     "linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>,
        "linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [PATCH] i2c: tegra: Wait for config load atomically while in ISR
Thread-Topic: [PATCH] i2c: tegra: Wait for config load atomically while in ISR
Thread-Index: AQHW6CIcSfsKH+/ghEGIVUc6PkdaV6oifElA
Date:   Mon, 11 Jan 2021 14:31:36 +0000
Message-ID: <a0b0f224c2864b80a5bac53646d67daf@AcuMS.aculab.com>
References: <20210111135547.3613092-1-mperttunen@nvidia.com>
In-Reply-To: <20210111135547.3613092-1-mperttunen@nvidia.com>
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From: Mikko Perttunen
> Sent: 11 January 2021 13:56
> 
> Upon a communication error, the interrupt handler can call
> tegra_i2c_disable_packet_mode. This causes a sleeping poll to happen
> unless the current transaction was marked atomic. Since
> tegra_i2c_disable_packet_mode is only called from the interrupt path,
> make it use atomic waiting always.

Spin-waiting in an ISR for anything that it makes sense to do
a sleep-wait for at other times is badly broken design.

	David

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