On 22/08/2021 19:40, Moustafa Nofal wrote:
>
>
> On Sunday, 22 August 2021 at 15:42:12 UTC+2 Ralf Ramsauer wrote:
>
>
>
> On 22/08/2021 12:45, Moustafa Nofal wrote:
> >
> > Hi,
> > I build Jailhouse on RPi4 using 5.3 Kernel and it is working nice. I
> > need to toggle a GPIO pin. I tried baremetal code but I figured out,
> > that I must map the peripheral using specifically this function:
> > p->mem_fd = open("/dev/mem", O_RDWR|O_SYNC);
> > So, I need the following headers to be included:
> > /*For munmap, MAP_FAILED, MAP_SHARED, PROT_READ, PROT_WRITE*/>
> #include <sys/mman.h>
> > /* For open(), creat() */
> > #include <unistd.h>
> > /* For O_RDWR */
> > #include <fcntl.h>
>
> >>Do I understand correctly, that you want those header in your inmate?
> I am not sure about it, but I needed to know the correct procedure.
Please do _not_ reply with html mails in future. It's almost impossible
to figure out where you exactly responded. And please always reply to all.
>
>
>
> > What could be a clean way, to add such headers into jailhouse, I
> have my
> > own header-which describes addresses of GPIO registers- added to
> > /inmates/lib/include, but is there any possible way to add these
> headers?
Sorry, I think I don't understand the question. Of course, if you have
custom modifications, you can place you headers there.
>
> >That's not the right approach to solve your issue. Having those
> standard
> >library functions means that you need tons of logic in your inmate,
> >including a fully-fledged operating systems.
>
> >What you actually want to do:
> >0. Pass the GPIO device to the inmate in your cell's config
> >1. Figure out the memory address of your GPIO controller + pin. For
> >reference, consider looking at datasheets or device trees.
>
>
> I have done this in the inmate file, read the datasheet and device tree
> and edited also the .dts file in jailhouse, I wonder, whether it is
> necessary.
The device tree is only required if you use Linux in your inmate. If you
want to use the bare-metal inmate library, then you only need to adjust
the configuration of your inmate.
>
> >2. Map that address to your inmate using map_range()
> >(instead of opening /dev/mem, there is no semantic at all for devices
> >in our tiny libinmate)
>
>
>
> Yes, that was my problem, I tried accessing the registers directly,
> but it must be mapped first, there are two solutions for this,
> either using assembly code or use such a function.
> I did not know about map_range, or whether jailhouse uses it, but I
> will check and get back to you.
map_range is a routine of libinmate, it /belongs/ to jailhouse. Use "git
grep map_range" to see how it is used.
> On the other hand, I found mmio_write32() for writing registers, but
> I could not find the source file. Also timer_start(), I do not know
> where is the definition of this function.
After you mapped the physical memory, you can then access registers with
mmio_write()-accessors. To find the definition of those routines, just
use git grep:
lib/arm-common/include/inmate.h:static inline void mmio_write32
> One more question, I think you must have mapped the timer and UART0
> peripherals, in order to be able to trigger it. I saw the memory
In order to trigger what? What is "it"? :)
> region structure in *rpi4-inmate-demo.c *and could understand, how
> could you make it and implemented something similar for the GPIO.
> But where the initialization of the timer and uart, I mean in which
> file, or how is that made
On arm, libinmate uses the platform timer. Take a look at
inmates/lib/arm-common/timing.c.
>
> >3. directly write to the address
>
> >Other than that, have a look at demos/arm/gic-demo.c or
> >demos/x86/apic-demo.c. There we have the cmdline argument that allows
> >for specifying a led-pin, which is nothing else but a GPIO.
> Yes, this part I understand, but my experience was with
> ARM-Cortex-M, so I thought I could just write to the register
> without mapping it. But thanks for the information and would really
> appreciate, if you could tell in which direction shall I dig.
On ARM, we use virtual memory management for inmates. So you definitely
need a mapping prior to accessing MMIO registers.
HTH,
Ralf
>
>
> >@Jan, BTW, I think I just found a bug in demos/arm/gic-demo.c: Since I
> >introduced arch_mmu_enable(), I forgot to map physical addresses for
> >map_range() for the led_reg. Will provide a patch soon…
>
> >Ralf
> Best regards,
> Moustafa Noufale
> >
> > Thanks in advance
> > Moustafa Noufale
> >
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Mit freundlichen Grüßen
Ralf Ramsauer
Labor für Digitalisierung
Fakultät für Informatik und Mathematik
Ostbayerische Technische Hochschule Regensburg
Galgenbergstrasse 32
93053 Regensburg
Tel.: +49 (0)941 943-9267
E-Mail: [email protected]
http://www.oth-regensburg.de
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