PS: Please create a new mailing list thread for discussing details regarding the UART driver. The subject of this one just isn't correct any more.
On 22/12/2019 09:50, Christian Mauderer wrote: > Hello Niteesh, > > thanks for the detailed information. I agree that this is a completely > different hardware module and will need a different driver. > > The data sheet (by the way: one of the worst I've ever seen) tells that > the Mini UART has "16550 like registers" that are "as far as possible > [...] like a 16550". So maybe the driver from > bsps/shared/dev/serial/ns16550.c can be used or extended. > > By the way: It's a really odd idea to integrate two completely different > UARTs into one chip. I know chips with variations but completely > different is unusual. Especially because most serial peripherals are > small and need very few chip area compared to memory. But maybe they had > a reason ... > > Best regards > > Christian > > > On 22/12/2019 08:12, Niteesh wrote: >> On raspberry pis equipped with the wireless/Bluetooth module, the PL011 >> is connected to the Bluetooth module, >> and the mini UART is used as the primary UART. On all other models, the >> PL011 is used as the primary UART. >> >> The mini UART has smaller FIFOs. Combined with the lack of flow control, >> this makes it more prone to losing characters at higher baudrates. It is >> also generally less capable than the PL011, mainly due to its baud rate >> link to the VPU clock speed. >> >> 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 >> >> https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf >> the official doc from broadcom, this is what I used while developing >> drivers for bare metal project. >> >> >> >> On Sun, Dec 22, 2019 at 1:56 AM Christian Mauderer <l...@c-mauderer.de >> <mailto:l...@c-mauderer.de>> wrote: >> >> I haven't had a look at the different types of UARTS yet. What is the >> difference? What do you use as reference? >> >> If it is just a variant of an existing driver, the existing one should >> be extended to support both variants. >> >> On 21/12/2019 20:45, Niteesh wrote: >> > On inspecting the code, the driver is for PL011. We have to write a >> > driver for the mini uart. >> > which we will have start from scratch. So, how do you want the >> structure >> > to be? >> > >> > The code of PL011 can be improved. We could use gpio functions to >> > configure pins. >> > And also many of the UART values are set in place instead of using the >> > appropriate function, for example >> > the usart_set_baud is empty and the baud rate is set directly in the >> > init function. >> > What do you think about these changes? Should we change them also? >> > On Sun, Dec 22, 2019 at 12:25 AM Christian Mauderer >> <l...@c-mauderer.de <mailto:l...@c-mauderer.de> >> > <mailto:l...@c-mauderer.de <mailto:l...@c-mauderer.de>>> wrote: >> > >> > On 21/12/2019 19:26, Niteesh wrote: >> > > There is already a PL011 driver in the arm shared section. >> should we >> > > just import it? >> > >> > If you say "import" and you mean "use" and not "copy": yes, >> that would >> > be great. >> > >> > > >> > > On Sat, Dec 21, 2019 at 10:46 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: >> > > >> > > Shall I start writing a driver for raspberrypi3 PL011? >> > > >> > > >> > > On Sat, Dec 21, 2019 at 8:40 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: >> > > >> > > On 19/12/2019 15:05, Christian Mauderer wrote: >> > > > On 19/12/2019 14:27, Sebastian Huber wrote: >> > > >> On 19/12/2019 14:24, Christian Mauderer wrote: >> > > >>> Hello, >> > > >>> >> > > >>> triggered by the discussion regarding RTEMS on >> > raspberrypi 3 >> > > I did some >> > > >>> tests. I haven't been able to start a RTEMS on >> my Pi 1 >> > if I >> > > tried a >> > > >>> version after commit >> > > c5fd79cd4704a4270ba0114a1009ab8556f997c9 from >> > > >>> 29.07.2019. Right before it everything works as >> expected. >> > > >>> >> > > >>> The commit changes the memory locations. From what I >> > > understood, the >> > > >>> bootloader on a raspberry always jumps to >> address 0x8000 >> > > after loading >> > > >>> the application. So I'm not convinced that the >> change is >> > > correct. >> > > >> >> > > >> Is the 0x8000 a fixed address or you configure >> this in >> > a boot >> > > image header? >> > > >> >> > > > >> > > >>From what I've seen the bootloader just uses a fixed >> > address. >> > > All guides >> > > > that I've found just use objcopy to generate a binary >> > from the >> > > elf files >> > > > without adding a header. For example a guide for >> RTEMS: >> > > > >> > > > >> > > > >> > > >> > >> >> http://alanstechnotes.blogspot.com/2013/03/running-your-first-rtems-program-on.html >> > > > >> > > > A FreeRTOS port mentions this behavior explicitly in a >> > comment >> > > in the >> > > > linker file: >> > > > >> > > > >> > > > >> > > >> > >> >> https://github.com/jameswalmsley/RaspberryPi-FreeRTOS/blob/master/raspberrypi.ld#L17 >> > > > >> > > > The "graphics processor" is no typo here. It seems the >> > > initialization is >> > > > really done by the graphics processor on the pi. >> > > > _______________________________________________ >> > > > 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 >> > > > >> > > >> > > I just found an option: It is possible to set a >> > "kernel_address" >> > > in the >> > > config.txt: >> > > >> > > >> > > >> > >> >> https://www.raspberrypi.org/documentation/configuration/config-txt/boot.md >> > > >> > > So the start address can be changed and maybe the >> adaption to >> > > the linker >> > > file isn't necessary. >> > > >> > >> > _______________________________________________ > devel mailing list > devel@rtems.org > http://lists.rtems.org/mailman/listinfo/devel > _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel
