From: David Brown <davidb@codeaurora.org>
To: Stephen Boyd <sboyd@codeaurora.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-serial@vger.kernel.org
Subject: Re: [PATCH 1/4] msm_serial: Fix NUL byte output on UARTDM
Date: Wed, 24 Jul 2013 13:29:44 -0700 [thread overview]
Message-ID: <20130724202944.GB10926@codeaurora.org> (raw)
In-Reply-To: <1374691051-28544-2-git-send-email-sboyd@codeaurora.org>
On Wed, Jul 24, 2013 at 11:37:28AM -0700, Stephen Boyd wrote:
>UARTDM serial devices require us to wait for the entire TX fifo
>to drain before we can change the contents of the NCF_TX
>register. Furthermore, if we write any characters to the TX fifo
>within the same clock cycle of changing the NCF_TX register the
>NCF_TX register won't latch properly.
>
>To fix these issues we should read back the NCF_TX register to
>delay any TX fifo accesses by a clock cycle and we should wait
>for the TX fifo to drain (instead of just waiting for the fifo to
>be ready to receive more characters). Failure to do so leads to
>random NUL bytes interspersed in the output.
>
>Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
>---
> drivers/tty/serial/msm_serial.c | 14 +++++++++-----
> drivers/tty/serial/msm_serial.h | 1 +
> 2 files changed, 10 insertions(+), 5 deletions(-)
Acked-by: David Brown <davidb@codeaurora.org>
--
sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation
WARNING: multiple messages have this Message-ID (diff)
From: davidb@codeaurora.org (David Brown)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/4] msm_serial: Fix NUL byte output on UARTDM
Date: Wed, 24 Jul 2013 13:29:44 -0700 [thread overview]
Message-ID: <20130724202944.GB10926@codeaurora.org> (raw)
In-Reply-To: <1374691051-28544-2-git-send-email-sboyd@codeaurora.org>
On Wed, Jul 24, 2013 at 11:37:28AM -0700, Stephen Boyd wrote:
>UARTDM serial devices require us to wait for the entire TX fifo
>to drain before we can change the contents of the NCF_TX
>register. Furthermore, if we write any characters to the TX fifo
>within the same clock cycle of changing the NCF_TX register the
>NCF_TX register won't latch properly.
>
>To fix these issues we should read back the NCF_TX register to
>delay any TX fifo accesses by a clock cycle and we should wait
>for the TX fifo to drain (instead of just waiting for the fifo to
>be ready to receive more characters). Failure to do so leads to
>random NUL bytes interspersed in the output.
>
>Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
>---
> drivers/tty/serial/msm_serial.c | 14 +++++++++-----
> drivers/tty/serial/msm_serial.h | 1 +
> 2 files changed, 10 insertions(+), 5 deletions(-)
Acked-by: David Brown <davidb@codeaurora.org>
--
sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation
next prev parent reply other threads:[~2013-07-24 20:29 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-24 18:37 [PATCH 0/4] msm_serial fixes and improvements Stephen Boyd
2013-07-24 18:37 ` Stephen Boyd
2013-07-24 18:37 ` [PATCH 1/4] msm_serial: Fix NUL byte output on UARTDM Stephen Boyd
2013-07-24 18:37 ` Stephen Boyd
2013-07-24 20:29 ` David Brown [this message]
2013-07-24 20:29 ` David Brown
2013-07-24 18:37 ` [PATCH 2/4] msm_serial: Fix sparse warnings Stephen Boyd
2013-07-24 18:37 ` Stephen Boyd
2013-07-24 20:30 ` David Brown
2013-07-24 20:30 ` David Brown
2013-07-24 18:37 ` [PATCH 3/4] msm_serial: Make baud_code detection more dynamic Stephen Boyd
2013-07-24 18:37 ` Stephen Boyd
2013-07-24 20:30 ` David Brown
2013-07-24 20:30 ` David Brown
2013-07-26 4:30 ` Bjorn Andersson
2013-07-26 4:30 ` Bjorn Andersson
2013-07-26 17:05 ` Stephen Boyd
2013-07-26 17:05 ` Stephen Boyd
2013-07-24 18:37 ` [PATCH 4/4] msm_serial: Send more than 1 character at a time on UARTDM Stephen Boyd
2013-07-24 18:37 ` Stephen Boyd
2013-07-24 20:31 ` David Brown
2013-07-24 20:31 ` David Brown
2013-07-24 20:31 ` [PATCH 0/4] msm_serial fixes and improvements David Brown
2013-07-24 20:31 ` David Brown
2013-07-29 9:31 ` Ivan T. Ivanov
2013-07-29 9:31 ` Ivan T. Ivanov
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