+Peter, Russell, and Matwey. I suggest you to ask people I added to the Cc list.
On Sat, Dec 26, 2015 at 6:17 PM, Ильяс Гасанов <[email protected]> wrote: > Hello. > > We are upgrading to the 4.1.x kernel for our smart metering appliance > project, which is based on TI's Sitara hardware (AM335x SoC), and I > decided to switch from omap-serial legacy driver to the newer > 8250-based one. It marginally increases throughput efficiency, CPU > cycle wise, among other goodies, but I'm looking to implement a rather > important feature that is present in the legacy driver, but the newer > one is lacking. > > Namely, our project makes use of RS232<->RS485 converters, which in > turn need to consume RTS signals to switch between Rx and Tx modes at > the RS485 side, due to the bus variant we use being half-duplex. > However, the already manufactured hardware is already designed to make > the use of certain pins to take the RTS signal from, which can only be > configured as GPIO for that purpose (in other words, no "native" UART > RTS) - and basically redesigning the h/w configuration now is > definitely out of question. The omap-serial driver already provides > FDT options for that, named "rts-gpio", "rs485-rts-active-high" etc. > > As far as I could ascertain, the 8250_omap driver (as well as the 8250 > framework itself) at the moment lacks the means to make use of GPIO > pins for that purpose. While trying to implement it myself, I noticed > that the legacy driver has it made in a comparably straightforward > approach, via dispatching the code to switch the pin in its .start_tx > and .stop_tx handlers, and some timing adjustments. Unfortunately, the > situation with 8250-based drivers is different - the aforementioned > handlers are provided by the 8250_core module and are common for all > drivers within the framework. > > At first, I thought that implementing such feature for the 8250 > framework itself sounds like a good idea, but after reading this > particular post: > http://lists.infradead.org/pipermail/linux-arm-kernel/2014-July/271377.html > I decided to comply with the point of view specified there. However, > I'm not that familiar with the 8250 framework internals (or serial > internals at all, for that matter), and my time is quite short, so I > would appreciate much any useful directions on how to do it > hardware-specific style, which functions/structs/handlers to use, etc. > Of particular interest is the following part: > >> I don't care whether the drive does it via serial_out magic or a more >> explicit hook but it doesn't belong here in core code. > > Any ideas/clarifications on what might be meant on that part? > > Regards, > Ilyas G. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- With Best Regards, Andy Shevchenko -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
