On Tue, Oct 9, 2018 at 5:30 PM Arnd Bergmann <a...@arndb.de> wrote:
>
> On Tue, Oct 9, 2018 at 11:20 AM Sunil Kovvuri <sunil.kovv...@gmail.com> wrote:
> >
> > On Tue, Oct 9, 2018 at 1:27 PM Arnd Bergmann <a...@arndb.de> wrote:
> > >
> > > On Tue, Oct 9, 2018 at 9:03 AM Sunil Kovvuri <sunil.kovv...@gmail.com>
> > > wrote:
> > > > On Mon, Oct 8, 2018 at 5:38 PM Arnd Bergmann <a...@arndb.de> wrote:
> > > > > On Sun, Oct 7, 2018 at 5:01 PM <sunil.kovv...@gmail.com> wrote:
> > > I think if you enable CONFIG_DEBUG_VIRTUAL, the virt_to_page()
> > > above should trigger a warning in
> > >
> > > phys_addr_t __virt_to_phys(unsigned long x)
> > > {
> > > WARN(!__is_lm_address(x),
> > > "virt_to_phys used for non-linear address: %pK (%pS)\n",
> > > (void *)x,
> > > (void *)x);
> > >
> > > return __virt_to_phys_nodebug(x);
> > > }
> > >
> > > Can you verify that?
> > >
> > > Arnd
> >
> > No, it isn't, as for 64bit systems CONFIG_SPARSEMEM_VMEMMAP is enabled.
>
> But that is also user-selectable, right? It still seems to be really
> fragile to rely on non-documented behavior of virt_to_phys()
> here, if that only works for some configurations.
>
> > But is there any alternative to what is being done ?
>
> I'm not completely sure, but there may be a way to do this correctly
> using the iommu API instead of the dma-mapping API. What you do
> here is fairly rare, but not unprecedented.
>
> Arnd
After further checking the only way i found is using dma_map_resource() which
accepts physical address and creates a mapping. Will test and submit next series
with the changes.
Thanks,
Sunil.
