Re: [Xen-devel] xen on beagleboard-x15: fails to access PRCM MPU register

[Denis Obrezkov <denisobrezkov@xxxxxxxxx>]

Hi Iain,

On 6/28/19 7:25 PM, Iain Hunter wrote:
> Hi Stefano,
> It was a patchset I'd circulated earlier in the GSoC process.
> Basically the partial port of Xen on X15 I'd done last year. The build
> script is the reference for which patches were actually used.
> Iain
I believe the reason we haven't started from trying your patch was that
I thought that since you hadn't used smp your solution might not work in
our case, since we want to have smp (I was probably wrong).
I think I should reproduce all the issues step-by-step that Iain faced
and apply his patches where they are required (otherwise it would be
hard for me to understand what's happening).

Stefano, Julien?
> 
> On Fri, 28 Jun 2019 at 17:02, Stefano Stabellini <sstabellini@xxxxxxxxxx> 
> wrote:
>>
>> Hi Iain,
>>
>> Where is the patch you mentioned? Maybe you forgot to attach it to the
>> email?
>>
>> Cheers,
>>
>> Stefano
>>
>> On Fri, 28 Jun 2019, Iain Hunter wrote:
>>> Stefano, Denis,
>>>
>>> I achieved that with patch
>>> patches/xen/0003-add-PRCM_MPU-to-memory-translation-for-AM572x.patch.
>>> This just adds
>>>  .specific_mapping=omap5_specific_mapping
>>> to DRA7 platform.
>>>
>>> Iain
>>>
>>> On Fri, 28 Jun 2019 at 01:33, Stefano Stabellini <sstabellini@xxxxxxxxxx> 
>>> wrote:
>>>>
>>>> Writing here a summary of the follow-up discussion on IRC.
>>>>
>>>> This is due to a magic memory region, not described in the device tree,
>>>> being accessed by Linux. The memory region is 0x48243400 - 0x48243400+512.
>>>>
>>>> To fix problems like this one, we have the platform specific files in
>>>> xen: see the files under xen/arch/arm/platforms/. Specifically, omap5.c
>>>> might be a good model for what we need. Look at the
>>>> omap5_specific_mapping function, which does exactly what the name
>>>> suggests: it maps special MMIO regions into the guest.
>>>>
>>>>  /* Additional mappings for dom0 (not in the DTS) */
>>>>  static int omap5_specific_mapping(struct domain *d)
>>>>  {
>>>>      /* Map the PRM module */
>>>>      map_mmio_regions(d, gaddr_to_gfn(OMAP5_PRM_BASE), 2,
>>>>                       maddr_to_mfn(OMAP5_PRM_BASE));
>>>>
>>>>      /* Map the PRM_MPU */
>>>>      map_mmio_regions(d, gaddr_to_gfn(OMAP5_PRCM_MPU_BASE), 1,
>>>>                       maddr_to_mfn(OMAP5_PRCM_MPU_BASE));
>>>>
>>>>      /* Map the Wakeup Gen */
>>>>      map_mmio_regions(d, gaddr_to_gfn(OMAP5_WKUPGEN_BASE), 1,
>>>>                       maddr_to_mfn(OMAP5_WKUPGEN_BASE));
>>>>
>>>>      /* Map the on-chip SRAM */
>>>>      map_mmio_regions(d, gaddr_to_gfn(OMAP5_SRAM_PA), 32,
>>>>                       maddr_to_mfn(OMAP5_SRAM_PA));
>>>>
>>>>      return 0;
>>>>  }
>>>>
>>>> We need something similar for 0x48243400 - 0x48243400+512 on
>>>> Beagleboard.
>>>>
>>>>
>>>> On Thu, 27 Jun 2019, Denis Obrezkov wrote:
>>>>> CC'ed other GSoC mentors
>>>>>
>>>>> On 6/27/19 9:52 PM, Denis Obrezkov wrote:
>>>>>> Hello all,
>>>>>>
>>>>>> I have a failure when I am trying to boot Linux with Xen on bb-x15, here
>>>>>> is the log:
>>>>>> https://pastebin.com/BBAFPkVU
>>>>>>
>>>>>> and, as Julien (cc'ed) suggested here is the DT debug information for 
>>>>>> xen:
>>>>>> https://drive.google.com/open?id=15YTsCKYUTbG2i-siWezJXKWuG0H1VfQz
>>>>>>
>>>>>> So, what I was able to figure out:
>>>>>> In omap4_prminst_read_inst_reg it tries to read from _prm_bases[part].va
>>>>>> (arch/arm/mach-omap2/prminst44xx.c).
>>>>>> _prm_bases[part].va has a value of prm_base or prcm_mpu_base depending
>>>>>> on part value(arch/arm/mach-omap2/prminst44xx.c:44)
>>>>>> Failure happens when _prm_bases[OMAP4430_PRCM_MPU_PARTITION] is read.
>>>>>> It's value set up in arch/arm/mach-omap2/prcm_mpu44xx.c:54.
>>>>>> The installed value is obtained with OMAP_L4_IO_ADDRESS macro
>>>>>> (mach_omap2/io.c:667). Here is its definition 
>>>>>> (arch/arm/mach_omap2/iomap.h):
>>>>>> #define OMAP2_L4_IO_OFFSET  0xb2000000
>>>>>> #define OMAP2_L4_IO_ADDRESS(pa) IOMEM((pa) + OMAP2_L4_IO_OFFSET) /* L4 */
>>>>>>
>>>>>> and IOMEM (arch/arm/include/asm/io.h):
>>>>>> #define IOMEM(x)    ((void __force __iomem *)(x))
>>>>>>
>>>>>> I don't understand what is happening and how to overcome it.
>>>>>>
>>>>>
>>>>> --
>>>>> Regards, Denis Obrezkov
>>>>>
>>>>>
>>>

-- 
Regards, Denis Obrezkov

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