On Tue, 2014-04-15 at 09:56 +0300, Heikki Krogerus wrote: > On Mon, Apr 14, 2014 at 03:54:31PM +0000, Poulain, Loic wrote: ... > > This problem seems due to the DMA usage. Indeed, when I disable > > the DMA manually in 8250_dw.c (up->dma = NULL), problem does not > > occur anymore, all baudrates are stable. > > I think this is the same issue Jin Yao (CC'd) already spotted. He made > a bug for it: > https://bugzilla.kernel.org/show_bug.cgi?id=73071 > > > Do you think a specific 8250 DMA configuration could apply for the byt > > case ? > > How/Where can I debug to know if the 8250 DMA works as expected ? > > Adding Andy. He maintains the Designware DMA Engine driver that is > used on BYT. He should be the best person to tell how to debug the > DMA. In case you have DYNAMIC_DEBUG enabled in the kernel configuration you may apply following addon to the kernel command line (considering that you have DW_DMAC_CORE=y and DW_DMAC=y): dw_dmac_core.dyndbg dw_dmac.dyndbg It enables the debug messages from the dw_dmac driver. P.S. in case you need deep debugging I have a custom patch which enables it for all IO communication done with the hardware (this apparently doesn't include dumps of data transfered). -- Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> Intel Finland Oy -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
