On Sat, Apr 25, 2015 at 3:08 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Saturday 25 April 2015 16:33:18 Joachim Eastwood wrote: >> >> One other question: What is the preferred way of describing different >> UART SoC features in DT? >> 16550a is used as base on most NXP Cortex-M devices, but each UART can >> have different features like; IRDA, Smart card, RS485, sync mode >> (USART), DMA, hardware RTS/CTS pins and full modem pins. >> Features also differ between UARTs on the same device. >> >> I am thinking about either using different comp strings or some kind >> of feature flags in DT. (Freescale UART already uses feature flags >> like: "fsl,irda-mode" and "fsl,uart-has-rtscts") > > I would probably specify both then, to give more flexibility to the > driver in implementing it one way or the other. > >> All UARTs on LPC1850 have RS485 and DMA support. In additional you have: >> UART0,2,3: sync mode and smart card. >> UART3: IRDA >> UART1: full modem control pin set. >> >> Comp strings could be something like: >> "nxp,lpc1850-usart" <- sync+smart card >> "nxp,lpc1850-usart-irda" <- sync+smart card+irda >> "nxp,lpc1850-uart-modem" <- modem-pins I'd only consider going this route if the UARTs are hard wired in the chip for these functions. But use of full modem signals is almost always optional. >> or feature flags like: >> nxp,sync-mode; >> nxp,rs485-mode; >> nxp,smart-card; >> nxp,irda-mode; >> nxp,full-modem; > > For cases where a single chip has uarts with different features, > using feature flags makes most sense, you can probably skip > assigning different compatible strings there. Agreed. I would add that if you find vendor specific flags like this that you also need, drop the vendor prefix and create something generic. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
