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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

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
> 
> 

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