On Wed, Oct 9, 2019 at 8:42 AM Vignesh Raghavendra <vigneshr@xxxxxx> wrote: > > Hi Adam, > > On 06/10/19 10:34 PM, Adam Ford wrote: > > Has anyone else had any issues using the CONFIG_SERIAL_8250_DMA on the OMAP? > > > > I can use the DMA on the legacy, omap-serial driver, but when I enable > > the DMA on the 8250-omap driver, I get missing frames in Bluetooth. > > > > The older driver seems to have an ISR that seems to address a variety > > of items compared to the very tiny ISR for 8250-omap.c. > > > > I am not exactly sure where to start, but if someone has any > > suggestions on how I can troubleshoot, please let me know. As of now, > > I have to disable CONFIG_SERIAL_8250_DMA to get the Bluetooth > > connected to UART2 operational on a DM3730 at 3,000,000 baud, but it > > appears to work just fine after some patches I just submitted for > > handling RTS/CTS. The legacy omap-serial driver works fine with DMA. > > > > Mainline omap-serial does not support DMA (evident from lack of > dmaengine API calls) and therefore is not a regression. So OMAP3 UART > DMA was never tested at least with 8250 driver. > I am not sure enabling UART DMA on OMAP3 would be a trivial job. We need > analyse of whether all erratas workarounds are implemented and see if > there any difference wrt DMA integration itself. Do we know if UART DMA > ever worked on OMAP3 previously? Can we disable CONFIG_SERIAL_8250_DMA from omap2plus_defconfig? As of right now, it's the only way I can use the Bluetooth. There are #ifdef's in the 8250-omap driver, so it looks like some of the hooks are there, but if it's incomplete, it seems like we shouldn't enable this config option by default yet. adam > > > adam > > > > -- > Regards > Vignesh
