Reset iMX53-QSB from the secure world

[Ofer Hasson]

I'll try it, thank you very much

On Thu, Sep 10, 2015 at 4:42 PM, Stefan Kalkowski <
stefan.kalkowski at ...1...> wrote:

> Hi Ofer,
>
> On 09/10/2015 10:21 AM, Ofer Hasson wrote:
> > Hey,
> >
> > I'm attempting to make a simple reboot feature on Freescale's iMX53-QSB.
> > I'm currently working using the tz_vmm example.
> > So, I understand that the way to achieve that on this board is through
> the
> > watchdog timer,
> > I followed the Linux kernel code that does this, and implemented a kernel
> > module that does only the reboot part, this what i came up with:
> > -
> > volatile unsigned short *wdog1_base = (volatile unsigned short*)
> 0xf7e98000;
> > *wdog1_base = (1 << 2);
> > -
> >
> > This exact code, i a kernel module, does an immediate reset and i get the
> > u-boot shell.
> > All of this is done on the normal world of course, now i wish to have
> this
> > in the secure world,
> > Running the exact same code in the secure world, in the handle hypercall
> > routine i get:
> > -
> > no RM attachment (faulter 129090 with IP 70014c28 attempts to write to
> > address f7e98000)
> > void Genode::Pager_object::unresolved_page_fault_occurred(): not
> implemented
> > unknown signal context
>
> The problem is that you took the virtual address the watchdog is mapped
> to within the Linux kernel, and try to access that address within
> Genode's HW kernel. That is why you see above page-fault message.
>
> The kernel is running with a configured MMU too, it is not disabled
> within the kernel. Moreover, the kernel does not have all physical
> memory mapped one-by-one automatically.
>
> Is there a hard constrain to do the reset within the kernel? It is much
> more convenient and easy to implement for instance within the platform
> driver. Because you do not need to extend the kernel syscall interface,
> or need an extra session interface within core. You could extend the
> platform driver interface instead.
>
> In general, what a driver needs to do to access the Watchdog registers
> is the following:
>
> # open an IOMEM session with the corresponding physical address
>   (bus address) of the watchdog device
> # map the IOMEM dataspace to a free virtual memory area
> # access the watchdog registers via the virtual addresses, it was
>   mapped to
>
> A convenient way is to use the Attached_mmio helper class. It does
> everything for you. Moreover, the MMIO framework (used in that class)
> allows you to define registers, and bit-magic in a more comprehensible
> fashion.
>
> The code to reset the board would look like the following:
>
>   #include <os/attached_mmio.h>
>
>   struct Watchdog : Genode::Attached_mmio
>   {
>        /* 16bit register at offset 0 */
>        struct Control : Register<0x0, 16> {
>
>            /* this Bitfield relates to (1 << 2) */
>            struct Enable : Bitfield<2, 1> {};
>        };
>
>        /*
>         * the physical address range of the watchdog has to be given to
>         * the attched_mmio base class (manual says: 0x53F98000, 0x1000)
>         */
>        Watchdog() :  Attached_mmio(WDOG_BASE, WDOG_SIZE) {}
>
>        void reset() { write<Control::Enable>(1); }
>   };
>
> Assuming that Linux is doing nothing more with the device, and the
> device is accessable from user mode, it should work to incorporate above
> snippet into the platform driver.
>
> Best Regards
> Stefan
>
> > -
> >
> > Any idea's how to achieve my reset from the secure world ?
> > Also, if someone could shed some light about the error, I'm not that
> > familiar with Genode, just starting to work with it.
> >
> > Thanks in advanced.
> >
> >
> >
> >
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>
> --
> Stefan Kalkowski
> Genode Labs
>
> http://www.genode-labs.com/ · http://genode.org/
>
>
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