From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 30 Nov 2009 23:57:39 +0000 From: Alan Cox To: Pavel Machek Cc: linux-bluetooth@vger.kernel.org, Marcel Holtmann , kernel list Subject: Re: bluetooth cf slow (10KB/sec), lots of dmesg spam Message-ID: <20091130235739.6dfa3d66@lxorguk.ukuu.org.uk> In-Reply-To: <20091129164450.GA1438@ucw.cz> References: <20091129155801.GA1634@ucw.cz> <20091130153915.0a6910e3@lxorguk.ukuu.org.uk> <20091129164450.GA1438@ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-ID: > ioctl(3, SNDCTL_TMR_START or TCSETS, {B921600 -opost -isig -icanon -echo ...}) = 0 It's certainly trying > > ...set 921K using TCSETS/B921600... and kernel says ok, but ... Careful: termios is one of those "gotcha" ioctls. It returns 0 to say "stuff happened" and returns a termios struct which contains the results - which may not be what you requested. So a set to an unsupported rate (too high for the chip clock) will produce a response of 0 and return the baud rate you actually got given. > ...we are still at 115200... I wonder if 921600 is the right speed to > use after all? Any other speeds I should try? (and can 400MHz arm > handle 921K on serial line?) It's pushing it on an x86 with a 16550A. You've got about 14 character times of worst case latency permitted and 14 x 10 bits isn't a lot at that rate. Some of the clones have much bigger FIFOs so it may depend what you actually have. Alan