On 24/12/2019 12:06, Niteesh wrote: > The current raspi console section is like this: > The bsp_console_select in console_select.c is responsible for selecting > between uart and the framebuffer. It does so > by setting the Console_port_minor. > The console_config is responsible for output_char function. > And other files are driver code. > If rewriting, this would be my approach, > Rewrite the bsp_console_select to set some kind of a variable like in > IMX, then in console_initialize function > link the right driver to /dev/console. > Replace the console_tbl with the device_context and console_fns with > termios_device_handlers and > finally add in the console_initialization function.
I agree that this would be a clean solution. So if you want you can do that. But there might is a hurdle: As far as I understood you you only have a Pi3? So you might have a hard time testing the changes. Maybe the simulator could work. Another possibility could be to set the "Console_port_minor" to something unused (for example -1). In that case you can define another /dev/console. Best regards and merry Christmas (in case you celebrate) Christian > > On Tue, Dec 24, 2019 at 2:13 PM Niteesh <gsnb...@gmail.com > <mailto:gsnb...@gmail.com>> wrote: > > Thank you so much, for such a detailed answer. Now things make > really good sense to me, > going through the code now is just a breeze. But I still have one > question > for the newer driver interface is console_initialize the function > which RTEMS calls while initializing > the console? Which means I can't mess with the name right? It is > similar to the main function, right? > > The current driver is a legacy one, how do you want me to proceed, > shall I rewrite the legacy to a > the new one, this is will be a great learning experience for me also > and we also get the BSP updated to the latest interface. > > > On Tue, Dec 24, 2019 at 3:20 AM Christian Mauderer > <l...@c-mauderer.de <mailto:l...@c-mauderer.de>> wrote: > > Hello Niteesh, > > quite a lot of questions. I'll try to answer them. Note that it > has been > some time since I had a detailed look at that code so if something I > tell seems odd please don't hesitate to question it. > > Please note that in RTEMS their are more or less two "levels" of > support > for a serial console: > > 1. A very basic polled system console (also known as > "debug-console" in > some BSPs). This one is used for printk and should work in basically > every case. It is used for critical system messages like > printing the > exception frame. For that a BSP has to provide a > "BSP_output_char" function. > > 2. A full featured UART driver integrated into Termios. That one > will be > used for all normal I/O on the UARTs. > > As far as I know the "console_tbl Console_Configuration_Ports" > belongs > to a table based legacy interface. It is handled in the file > bsps/shared/dev/serial/legacy-console.c. I'm not sure whether it is > documented in the BSP guide because it shouldn't be used for new > BSPs. > Same is true for the "major" and "minor" stuff: It's not really > used for > new drivers. > > Newer drivers use the initialization that is described in the manual > that you have already found. Basically they use > "rtems_termios_device_install" to register a new UART as > "/dev/ttySomething". Some recent (ARM) BSPs that do that are the > imx or > the atsam. > > The console that is used for stdin, stdout and stderr (printf, > scanf, > ...) is the one called "/dev/console" (defined in > CONSOLE_DEVICE_NAME). > For the legacy table based interface it's the one with the index of > "Console_Port_Minor". > > > If you want to access any UART other than the one for stdin and > stdout > you do that the same way like on Linux: Just use the "open" > function on > the "/dev/ttySomething" and use "read", "write" and simmilar or use > "fopen" together with "fread", "fwrite", "fprintf", ... > > > "printf" (and family) is a function belonging to the C library. > In our > case that's newlib. It will format your message and after some other > preprocessing will call the "write" function of the file that is > opened > as stdout (which is "/dev/console" in the default case). > > > I hope that I helped you with that explanation. Please feel free > to ask > anything if it isn't clear. > > Best regards > > Christian > > On 23/12/2019 19:50, Niteesh wrote: > > And finally, how does printf work? It is a macro? In that > case, how does > > any write to > > a console work? > > > > On Tue, Dec 24, 2019 at 12:18 AM Niteesh <gsnb...@gmail.com > <mailto:gsnb...@gmail.com> > > <mailto:gsnb...@gmail.com <mailto:gsnb...@gmail.com>>> wrote: > > > > Is the correct port minor number set during the > initialization? What > > is the application want's to > > access some other port? > > > > On Tue, Dec 24, 2019 at 12:16 AM Niteesh > <gsnb...@gmail.com <mailto:gsnb...@gmail.com> > > <mailto:gsnb...@gmail.com <mailto:gsnb...@gmail.com>>> wrote: > > > > I would like to clarify my doubts regarding the > console driver. > > I went through the documentation > > for the console > > > driver > https://docs.rtems.org/branches/master/bsp-howto/console.html#introduction. > > But it is quite different from how some BSPs initialize. > > Correct me if I am wrong > > The console_tbl contains the various entries of serial > ports. > > The console_fns is a struct of function pointers, > which point to > > the BSP uart functions. > > The BSP_output_char_function_type is what will be > called for > > printing a char on to the console. > > How does RTEMS initialize the uart? It's seems not to > be same > > for all BSPs. > > The doc says that the driver's initialization function > is called > > once during the rtems initialization process. > > The console init function install the serial driver using > > rtems_termios_device_install but there seems to be > > no such function in the raspberry pi? But there is a > entry in > > console_fns for init function, but then how does it > > gets called? > > And for BSP's with multiple serial's, the output function > > chooses the right serial using console_port_minor, > > Is it during initialization? > > What is the need for get and set register functions? > > > > On Mon, Dec 23, 2019 at 1:04 AM Christian Mauderer > > <l...@c-mauderer.de <mailto:l...@c-mauderer.de> > <mailto:l...@c-mauderer.de <mailto:l...@c-mauderer.de>>> wrote: > > > > On 22/12/2019 19:45, Joel Sherrill wrote: > > > > > > > > > On Sun, Dec 22, 2019, 12:29 PM Niteesh > <gsnb...@gmail.com <mailto:gsnb...@gmail.com> > > <mailto:gsnb...@gmail.com <mailto:gsnb...@gmail.com>> > > > <mailto:gsnb...@gmail.com > <mailto:gsnb...@gmail.com> <mailto:gsnb...@gmail.com > <mailto:gsnb...@gmail.com>>>> wrote: > > > > > > On Sun, Dec 22, 2019 at 8:44 PM Christian > Mauderer > > > <l...@c-mauderer.de > <mailto:l...@c-mauderer.de> <mailto:l...@c-mauderer.de > <mailto:l...@c-mauderer.de>> > > <mailto:l...@c-mauderer.de > <mailto:l...@c-mauderer.de> <mailto:l...@c-mauderer.de > <mailto:l...@c-mauderer.de>>>> wrote: > > > > > > Hello Niteesh, > > > > > > thanks for doing that work. > > > > > > On 22/12/2019 12:10, Niteesh wrote: > > > > The rpi1 and rpi2 use the PL011 UART, > whereas, > > with RPI's > > > equipped with > > > > wireless/Bluetooth module, the PL011 is > > connected to the Bluetooth > > > > module, and the mini UART is used as > the primary > > UART. > > > > > > In my opinion it would be great if you > could use > > the FDT to > > > distinguish > > > between the boards. That should allow to add > > raspberry 3 (and > > > maybe 4) > > > support without adding another BSP. More > BSPs mean > > a bigger > > > maintenance > > > effort for the RTEMS community. > > > > > > Learning more about FDT is on my list for a long > > time. I would love > > > to work on that > > > but I have almost no exp with FDT's. > > > But another thing could also be done, in > > > raspberrypi/start/bspstart.c we get the > revision and > > > model of the board using the mailbox. Every > board has > > a unique id, > > > which we could use to initialize > > > the BSP. But using FDT seems to be a more > elegant > > option, it is a > > > lot of work I think, but we could take > > > help from libbsd and linux I suppose. What > do you think? > > > > > > > > > I think there are almost always two steps to a > project > > like this: get it > > > to work and make it nice. :) > > > > > > If you fix the startup code to read the board > revision and > > memory size, > > > you can get a working BSP that dynamically > adapts to the > > models and > > > memory variations with minimal modifications. If > you want > > to then > > > convert the BSP to FDT, it will be a LOT easier > to debug > > with a working BSP. > > > > > > Plus you may be able to identify every variation > point > > based on just the > > > model info. Then FDT is just a matter of > switching the > > source of > > > some/all of the info. > > > > > > That would be my work plan anyway. > > > > I agree with Joel that a secure development basis > (also > > known as "hack") > > as a first step is a good idea. You maybe even > just make the > > mini UART > > the default driver while you are developing. Then > you can be > > sure that > > you have the right driver. > > > > As soon as that works you can either change to the > revision > > method or > > (better) to the FDT one and after that the patches > can be > > merged. Using > > the FDT isn't that complicated. Basically you > search for a > > node based on > > different parameters. For an example you can take > a look at > > the imx BSP. > > In imx_uart_probe > (bsps/arm/imx/console/console-config.c) a > > fdt node is > > searched and based on that a UART driver is used. > But again: > > Follow > > Joels suggestion to start simple and secure. > > > > > > > > > > > > > > > > > > > > https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf > > > > But from the above doc (PAGE 10), the > mini uart > > has 16550 like > > > registers > > > > and RTEMS already has the driver for it > > > > bsps/shared/dev/serial/ns16550.c. But > I am not > > sure how > > > compatible they > > > > are? Should a new driver be > implemented from > > scratch or use > > > ns16550 if > > > > possible? > > > > > > In general it's better to re-use > existing code. > > That has multiple > > > advantages: > > > > > > - It reduces the maintenance effort. > Fewer code > > means fewer work. > > > - If you have multiple driver for the > same or > > similar hardware > > > it can > > > happen that a bug is fixed in one but > not the other. > > > - It's simpler to find a hardware to > test changes. > > > - The driver becomes more universal with > every new > > supported > > > hardware. > > > That increases the chance that it fits > the next > > new hardware. > > > > > > I'm sure there are some more if you ask > someone else. > > > > > > I do understand the issues, I just spent > some time > > reading the > > > driver code. > > > I think we could most probably use it. I > will take a > > closer look and > > > will update. > > > > > > > Great. > > > > > > > > > > > > > > > > Also, the core clock on which the > PL011 is based > > on is changed > > > in rpi3. > > > > Rpi1 and 2 use 250Mhz as the default > clock but > > it was changed > > > to 400Mhz > > > > in Rpi3 and newer > > > > > > Again: Would be great if that could be > adapted > > based on FDT or by > > > reading the right registers. > > > > > > > > > > > Few differences between PL011 and Mini > uart > > > > The mini UART has smaller FIFOs. > Combined with > > the lack of > > > flow control, > > > > this makes it more prone to losing > characters at > > higher baud > > > rates. It > > > > is also generally less capable than > the PL011, > > mainly due to > > > its baud > > > > rate link to the VPU clock speed. > > > > > > That shouldn't really be a problem for > the system > > console. > > > > > > > > > > > The particular deficiencies of the > mini UART > > compared to the > > > PL011 are : > > > > > > > > No break detection > > > > No framing errors detection > > > > No parity bit > > > > No receive timeout interrupt > > > > No DCD, DSR, DTR or RI signals > > > > > > > > > > _______________________________________________ > > > devel mailing list > > > devel@rtems.org <mailto:devel@rtems.org> > <mailto:devel@rtems.org <mailto:devel@rtems.org>> > > <mailto:devel@rtems.org <mailto:devel@rtems.org> > <mailto:devel@rtems.org <mailto:devel@rtems.org>>> > > > http://lists.rtems.org/mailman/listinfo/devel > > > > > > _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel
