The ns16550_context already has a field named baud_divisor, so if the user passes value for it, then we can skip the GetBaudDivisor function and use that value instead.
Is this approach okay? On Mon, Jan 13, 2020 at 3:46 PM Niteesh <gsnb...@gmail.com> wrote: > On Mon, Jan 13, 2020 at 1:38 PM Christian Mauderer < > christian.maude...@embedded-brains.de> wrote: > >> On 12/01/2020 21:26, Niteesh wrote: >> > On Sun, Jan 12, 2020 at 11:42 PM Christian Mauderer <l...@c-mauderer.de >> > <mailto:l...@c-mauderer.de>> wrote: >> > >> > Hello Niteesh, >> > >> > On 12/01/2020 16:06, Niteesh wrote: >> > > The only issue, I faced while using this driver is the baud >> divisor is >> > > calculated >> > > by CLOCK_FREQ/(BAUD_RATE * 16) (*ns16550-context.c:68)* >> > > but it should BAUD_DIV = (CLOCK_FREQ/(8 * BAUD_RATE)) - 1, for >> Rpi3. >> > > For testing, I assigned the baud divisor to 270 (115200 bits/s) in >> > > ns16550-context.c, >> > > and everything works fine. >> > >> > Sounds great. In NS16550_GetBaudDivisor there is already a case >> where >> > the baudDivisor is calculated differently (depending on >> > ctx->has_precision_clock_synthesizer and >> > ctx->has_fractional_divider_register). If none of the two cases are >> ok >> > for the controller you could just add another one. >> > >> > Can we pass in a function, which gets called, won't this be more >> > flexible? because >> > in the future if we have some other board that has a different >> > calculation for the baud rate >> > the function will take care of it. >> >> It's possible. Please make sure to be compatible with the current API. >> For example if the pointer is NULL you should call the legacy function >> instead. >> > > I will be adding an extra field, a function pointer to ns16550_context, > the prototype of the function would be *uint32_t calculate_baud_divisor( > ns16550_context * )* > This is will calculate the baud divisor using its own formula and the > initial baud. > If this function is not NULL then it would be called inside > *NS16550_GetBaudDivisor* function, > > > >> > > >> > > For console selection, my plan is to search for the aux node using >> > > compatible >> > > property and if its status is enabled, then initialize the AUX >> > uart and >> > > set the BSP_output_char >> > > to aux_output_char, else pl011_output_char. All this will be done >> > inside >> > > the uart_probe function, >> > > except for the initialization of AUX which will be done in >> > init_ctx_aux. >> > > And finally, call the output char >> > > function using *BSP_output_char. Do you have any neat way to do >> this? >> > >> > I don't have an example for a similar case at hand. So: No, no neat >> way >> > that I can tell you. >> > >> > Before you start to write code: Please take a look at the different >> > beagle variants what is possible. Is there a variant where AUX uart >> > would be there but shouldn't be used as a console (one of the Zeros >> > maybe or the compute module?). How does Raspbian or FreeBSD decide >> which >> > port should be used? Maybe they decide based on the >> commandline.txt? In >> > such a case it would be better to just initialize all active (in the >> > fdt) serial ports and decide based on the commandline too. >> > >> > >> > The Documentation says the following: >> > *By default, on Raspberry Pis equipped with the wireless/Bluetooth* >> > *module (Raspberry Pi 3 and Raspberry Pi Zero W), **the PL011 UART is* >> > *connected to the Bluetooth module, while the mini UART is used as the >> > primary UART and* >> > *will have a Linux console on it. On all other models, the PL011 is used >> > as the primary UART. >> > >> > * >> > *In Linux device terms, by default, /dev/ttyS0 refers to the mini UART, >> > and /dev/ttyAMA0 refers* >> > *to the PL011. The primary UART is the one assigned to the Linux >> > console, which depends on* >> > *the Raspberry Pi model as described above. There are also symlinks: >> > /dev/serial0, which always* >> > *refers to the primary UART (if enabled), and /dev/serial1, which >> > similarly always refers to the secondary UART (if enabled).* >> > * >> > * >> > I checked in all the DTB files, by decompiling them (files are >> > from https://github.com/raspberrypi/firmware/tree/master/boot). >> > In all board with support for wireless and bluetooth, the AuX is enabled >> > and serial0 points to it. So we could use serial0 >> > to find the correct UART port. I think this is solid enough. So, should >> > I use this approach? >> >> Sounds OK. If possible please initialize the other UART too if it is >> enabled in the FDT. Although we don't support bluetooth yet maybe there >> will be support in the future or someone wants to do it in the >> application. >> > I will go with this method then. > >> > >> > Or if using the command line, then we need to move the link to >> > CONSOLE_DEVICE to console_initialize, and parse the >> > command line twice. If this is no problem, then we could use this >> > approach also. >> >> Would be possible too. >> >> > >> > > >> > > And why don't we have a function similar >> to *of_device_is_available*, >> > > since there will be more and more >> > > FDT based boards, this will be really helpful. >> > >> > I agree that it would be helpful. Seems that you just found a >> function >> > that should be in a FDT framework. >> > >> > RTEMS currently only has the basic libfdt functions and some RTEMS >> > specific ones. The of_... functions belong to the FreeBSD "Open >> Firmware >> > Bus" which is an abstraction layer on top of FDT. It would be great >> to >> > identify useful ones and port them or provide an RTEMS >> implementation. >> > Like already discussed this could be part of a GSoC project. >> > >> > Best regards >> > >> > Christian >> > >> > > >> > > On Sun, Jan 5, 2020 at 12:57 AM Christian Mauderer >> > <l...@c-mauderer.de <mailto:l...@c-mauderer.de> >> > > <mailto:l...@c-mauderer.de <mailto:l...@c-mauderer.de>>> wrote: >> > > >> > > On 04/01/2020 09:32, Niteesh wrote: >> > > > We could now run RTEMS on Rpi3. I tried examples from the >> > samples >> > > > section and they run >> > > > fine. But still, a lot of functionality has to tested since >> it >> > > uses the >> > > > RPI2 BSP. To test these examples >> > > > I used a simple driver for the AUX. >> > > > The documentation from BCM link >> > > > >> > > >> > < >> https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf >> > (pg >> > > > no 10) states that >> > > > >> > > > >> > > > *The implemented UART is not a 16650 compatible UART >> However >> > > as far >> > > > as possible the first 8 control and status registers are >> > laid out >> > > > like a 16550 UART.* >> > > >> > > It also tells >> > > >> > > "Al 16550 register bits which are not supported can be >> > written but >> > > will be ignored and read back as 0. All control bits for >> > simple UART >> > > receive/transmit operations are available." >> > > >> > > So I would expect that not everything works like expected (for >> > example >> > > setting DCD, DSR, DTR, RI - they are not there for the mini >> > UART) but >> > > the basic stuff should work. >> > > >> > > > >> > > > >> > > > My question is can we use the existing ns16550 driver or >> > should I >> > > create >> > > > a new one? I also checked the address of the registers the >> > offsets >> > > don't >> > > > seem right to me, but someone should check and correct me if >> > I am >> > > wrong. >> > > >> > > If you compare the registers in the existing driver >> > > (NS16550_RECEIVE_BUFFER, ... in ns16550_p.h) and the one in >> > the BCM >> > > datasheet the registers look very similar (at least from the >> > position / >> > > function). I haven't done a bit by bit comparison yet. Please >> > note that >> > > you have to do a conversion between the defines and register >> > addresses. >> > > The define gives you a register index for a 32bit register. So >> > you have >> > > to multiply by 4 to get an address. The driver is designed >> > that you >> > > provide a setRegister and getRegister function that can do >> this >> > > conversion. >> > > >> > > Where did you find differences? >> > > >> > > I would suggest to just try the driver. >> > > >> > >> > >> > _______________________________________________ >> > devel mailing list >> > devel@rtems.org >> > http://lists.rtems.org/mailman/listinfo/devel >> > >> >> -- >> -------------------------------------------- >> embedded brains GmbH >> Herr Christian Mauderer >> Dornierstr. 4 >> D-82178 Puchheim >> Germany >> email: christian.maude...@embedded-brains.de >> Phone: +49-89-18 94 741 - 18 >> Fax: +49-89-18 94 741 - 08 >> PGP: Public key available on request. >> >> Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG. >> >
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