Reset iMX53-QSB from the secure world

[Ofer Hasson]

I forgot to update, it works perfectly, thank you so much !

On Fri, Sep 11, 2015 at 7:39 AM, Ofer Hasson <hassonof at ...310...>
wrote:

> 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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>> >
>> >
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>>
>> --
>> Stefan Kalkowski
>> Genode Labs
>>
>> http://www.genode-labs.com/ · http://genode.org/
>>
>>
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