From: stefan.wahren@i2se•com (Stefan Wahren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v3] serial: mxs-auart: keep the AUART unit in reset state when not in use
Date: Thu, 16 Jul 2015 17:36:17 +0200 [thread overview]
Message-ID: <55A7CF71.7050507@i2se.com> (raw)
In-Reply-To: <1437032458-8577-1-git-send-email-jbe@pengutronix.de>
> Whenever the UART device driver gets closed from userland, the driver
> disables the UART unit and then stops its clock to save power.
>
> The bit which disabled the UART unit is described as:
>
> "UART Enable. If this bit is set to 1, the UART is enabled. Data
> transmission and reception occurs for the UART signals. When the
> UART is disabled in the middle of transmission or reception, it
> completes the current character before stopping."
>
> The important part is the "it completes the current character". Whenever
> a reception is ongoing when the UART gets disabled (including the clock
> off) the statemachine freezes and "remembers" this state on the next
> open() and re-enabling of the unit's clock.
>
> In this case we end up receiving an additional bogus character
> immediately.
>
> The solution in this change is to move the AUART unit into its reset
> state on close() and only release it from its reset state on the next
> open().
>
> Signed-off-by: Juergen Borleis <jbe@pengutronix•de>
> ---
Acked-by: Stefan Wahren <stefan.wahren@i2se•com>
Thanks
Stefan
next prev parent reply other threads:[~2015-07-16 15:36 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-16 7:40 [PATCH v3] serial: mxs-auart: keep the AUART unit in reset state when not in use Juergen Borleis
2015-07-16 15:36 ` Stefan Wahren [this message]
2015-07-17 13:10 ` Peter Hurley
2015-07-17 14:35 ` Philipp Zabel
2015-07-20 8:04 ` Juergen Borleis
2015-07-20 13:00 ` Peter Hurley
2015-07-20 13:18 ` Juergen Borleis
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