From: Alan Cox <alan@linux.intel.com>
To: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
Cc: gregkh@linuxfoundation.org, linux-serial@vger.kernel.org,
linux-kernel@vger.kernel.org, Vineet.Gupta1@synopsys.com
Subject: Re: [PATCH] tty/8250_early: Prevent rounding error in uartclk to baud ratio
Date: Fri, 28 Sep 2012 14:03:28 +0100 [thread overview]
Message-ID: <20120928140328.4ff68806@bob.linux.org.uk> (raw)
In-Reply-To: <1348834748-31565-1-git-send-email-abrodkin@synopsys.com>
On Fri, 28 Sep 2012 16:19:08 +0400
Alexey Brodkin <Alexey.Brodkin@synopsys.com> wrote:
> Modify divisor to select the nearest baud rate divider rather than the
> lowest. It minimizes baud rate errors especially on low UART clock
> frequencies.
>
> For example, if uartclk is 33000000 and baud is 115200 the ratio is
> about 17.9 The current code selects 17 (5% error) but should select 18
> (0.5% error).
>
> On the same lines as following:
> http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.9-rc3/2.6.9-rc3-mm2/broken-out/serial-pick-nearest-baud-rate-divider.patch
>
> Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Seems sensible to me.
Acked-by: Alan Cox <alan@linux.intel.com>
WARNING: multiple messages have this Message-ID (diff)
From: Alan Cox <alan@linux.intel.com>
To: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
Cc: <gregkh@linuxfoundation.org>, <linux-serial@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <Vineet.Gupta1@synopsys.com>
Subject: Re: [PATCH] tty/8250_early: Prevent rounding error in uartclk to baud ratio
Date: Fri, 28 Sep 2012 14:03:28 +0100 [thread overview]
Message-ID: <20120928140328.4ff68806@bob.linux.org.uk> (raw)
In-Reply-To: <1348834748-31565-1-git-send-email-abrodkin@synopsys.com>
On Fri, 28 Sep 2012 16:19:08 +0400
Alexey Brodkin <Alexey.Brodkin@synopsys.com> wrote:
> Modify divisor to select the nearest baud rate divider rather than the
> lowest. It minimizes baud rate errors especially on low UART clock
> frequencies.
>
> For example, if uartclk is 33000000 and baud is 115200 the ratio is
> about 17.9 The current code selects 17 (5% error) but should select 18
> (0.5% error).
>
> On the same lines as following:
> http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.9-rc3/2.6.9-rc3-mm2/broken-out/serial-pick-nearest-baud-rate-divider.patch
>
> Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Seems sensible to me.
Acked-by: Alan Cox <alan@linux.intel.com>
next prev parent reply other threads:[~2012-09-28 13:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-28 12:19 [PATCH] tty/8250_early: Prevent rounding error in uartclk to baud ratio Alexey Brodkin
2012-09-28 12:19 ` Alexey Brodkin
2012-09-28 13:02 ` Jiri Slaby
2012-09-29 6:40 ` Vineet Gupta
2012-09-29 6:40 ` Vineet Gupta
2012-09-29 7:07 ` Jiri Slaby
2012-09-29 11:04 ` Vineet Gupta
2012-09-29 11:04 ` Vineet Gupta
2012-09-28 13:03 ` Alan Cox [this message]
2012-09-28 13:03 ` Alan Cox
-- strict thread matches above, loose matches on Subject: below --
2012-09-28 12:03 Alexey Brodkin
2012-09-28 12:03 ` Alexey Brodkin
2012-09-28 13:01 ` Jiri Slaby
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