From: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
To: Alex Elder <elder@linaro.org>
Cc: gregkh@linuxfoundation.org, heikki.krogerus@linux.intel.com,
david.daney@cavium.com, loic.poulain@intel.com,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] serial: 8250_dw: support high baudrates if possible
Date: Tue, 1 Jul 2014 23:02:59 +0100 [thread overview]
Message-ID: <20140701230259.23f2f452@alan.etchedpixels.co.uk> (raw)
In-Reply-To: <53AF227C.3000102@linaro.org>
On Sat, 28 Jun 2014 15:15:56 -0500
Alex Elder <elder@linaro.org> wrote:
> On 06/28/2014 10:36 AM, One Thousand Gnomes wrote:
> > On Fri, 27 Jun 2014 12:25:20 -0500
> >> + rate = 16 * max(115200U, (unsigned int)baud);
> >> +
> >
> > This assumes an arbitarily configurable clock, which is not I think the
> > usual case.
>
> If the clock's rate can't change, this will return an error,
> and the recorded rate (p->uartclk) will not be changed.
Which assumes an arbitrarily configurable clock, whereas you want to find
the correct clock and multiplier combination for the baud rate.
Most of these ports are wired to fixed clocks (which is fine) or clocks
with limited numbers of supported frequencies (which is not).
Your patch is an improvement but doesn't really fix the overall problem.
If we have enough devices with variable clocks for it to be useful then
fine - but can we merge it with a big FIXME note so that whoever comes
along wondering why their clock doesn't work or behaves very oddly can
figure it out and fix that case ?
Alan
next prev parent reply other threads:[~2014-07-01 22:02 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-27 17:25 [PATCH] serial: 8250_dw: support high baudrates if possible Alex Elder
2014-06-28 15:36 ` One Thousand Gnomes
2014-06-28 20:15 ` Alex Elder
2014-07-01 22:02 ` One Thousand Gnomes [this message]
2014-07-02 0:15 ` Alex Elder
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