Andy, The half of what is described here are implemented in my patches. But I cannot understand the other half. Each of six AM335x UARTs has RTS/CTS pins which are controlled by pinmux in device tree, no magic required here.
2015-12-27 15:47 GMT+03:00 Andy Shevchenko <[email protected]>: > +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 > -- With best regards, Matwey V. Kornilov. Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia 119991, Moscow, Universitetsky pr-k 13, +7 (495) 9392382 -- 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/
