Messages in this thread | | | Date | Wed, 18 Jun 2008 00:33:21 +0300 | From | "Nameer Yarkon" <> | Subject | Re: Serial problem and request for guidance.. |
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On Mon, Jun 16, 2008 at 3:03 PM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote: >> Some of my serial rx data gets lost. > > Which hardware ?
It's a range of platforms/kernel versions and scenarios. Currently it happens with a bluetooth device connected to standard UART on ARM (OMAP) with an old 2.6.14 kernel, but only when I enable the debug macros of the line discipline code (hci_h4, hci_ldisc,..). When a big chunk of data arrives, more than half of it is lost. even on 115200. But when I turn of the debug macros (BT_DBG macros which are simply a bunch of prinks) the problem disappears. So I suspect there are some nasty timing issues which lead to data loss.
I encountered similar problems last year even on a PC, with pre 2.6.21 kernels (around 2.6.19 or even earlier IIRC) but it was all gone with 2.6.21 and 2.6.22. Currently I have totally different machines, and these devices tend now to come with USB-to-serial connectors so I'm not quite sure about up-to-date kernels yet.
All I can say is that it is nasty and very hard to debug, and I'm not quite sure how can I debug it as I find the serial/tty subsystems a bit perplexing.
I know this is not necessarily relevant to the tip of the kernel, and it still lacks many details, but any guidance towards how can I debug it will be much appreciated. If I will successfully reproduce it with a current kernel I promise a full and detailed bug report.
Thank you for your time and patience ! Nameer.
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