On Sun, Jan 12, 2020 at 11:42 PM Christian Mauderer <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. > > > > 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? 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. > > > > 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>> 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. > > >
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