From: Wolfram Sang <wsa@kernel.org>
To: Mark Jonas <mark.jonas@de.bosch.com>
Cc: Support Opensource <support.opensource@diasemi.com>,
Lee Jones <lee.jones@linaro.org>,
linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org,
Adam.Thomson.Opensource@diasemi.com,
stwiss.opensource@diasemi.com, marek.vasut@gmail.com,
tingquan.ruan@cn.bosch.com, hubert.streidl@de.bosch.com
Subject: Re: [PATCH v5] mfd: da9063: Support SMBus and I2C mode
Date: Mon, 15 Mar 2021 19:31:15 +0100 [thread overview]
Message-ID: <20210315183115.GA2343@kunai> (raw)
In-Reply-To: <20210315160903.799426-1-mark.jonas@de.bosch.com>
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On Mon, Mar 15, 2021 at 05:09:03PM +0100, Mark Jonas wrote:
> From: Hubert Streidl <hubert.streidl@de.bosch.com>
>
> By default the PMIC DA9063 2-wire interface is SMBus compliant. This
> means the PMIC will automatically reset the interface when the clock
> signal ceases for more than the SMBus timeout of 35 ms.
>
> If the I2C driver / device is not capable of creating atomic I2C
> transactions, a context change can cause a ceasing of the clock signal.
> This can happen if for example a real-time thread is scheduled. Then
> the DA9063 in SMBus mode will reset the 2-wire interface. Subsequently
> a write message could end up in the wrong register. This could cause
> unpredictable system behavior.
>
> The DA9063 PMIC also supports an I2C compliant mode for the 2-wire
> interface. This mode does not reset the interface when the clock
> signal ceases. Thus the problem depicted above does not occur.
>
> This patch tests for the bus functionality "I2C_FUNC_I2C". It can
> reasonably be assumed that the bus cannot obey SMBus timings if
> this functionality is set. SMBus commands most probably are emulated
> in this case which is prone to the latency issue described above.
>
> This patch enables the I2C bus mode if I2C_FUNC_I2C is set or
> otherwise keeps the default SMBus mode.
>
> Signed-off-by: Hubert Streidl <hubert.streidl@de.bosch.com>
> Signed-off-by: Mark Jonas <mark.jonas@de.bosch.com>
From an I2C point of view, this is the correct approach:
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
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next prev parent reply other threads:[~2021-03-15 18:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-15 16:09 [PATCH v5] mfd: da9063: Support SMBus and I2C mode Mark Jonas
2021-03-15 18:31 ` Wolfram Sang [this message]
2021-03-16 7:21 ` Lee Jones
2021-03-16 8:23 ` Jonas Mark (BT-FIR/ENG1-Grb)
2021-03-16 9:54 ` Lee Jones
2021-03-16 9:54 ` Lee Jones
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