Re: runtime check for omap-aes bus access permission (was: Re: 3.13-rc3 (commit 7ce93f3) breaks Nokia N900 DT boot)

["Pali Rohár" <pali.rohar@gmail.com>]

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On Wednesday 11 February 2015 21:43:42 Pavel Machek wrote:
> Hi!
> 
> On Sun 2015-02-01 09:56:28, Pali Rohár wrote:
> > On Sunday 01 February 2015 02:36:06 Matthijs van Duin wrote:
> > > On 31 January 2015 at 20:06, Pali Rohár
> > > <pali.rohar@gmail.com>
> > > 
> > > wrote:
> > > > I have configured two testing N900 devices. One with
> > > > signed bootloader which enable omap aes support and one
> > > > device with signed bootloader which does not enable
> > > > omap aes support.
> > > 
> > > I'm probably missing some context here, but why not just
> > > use the one with aes support? Alternatively, one may
> > > argue that it's the bootloader's job to provide the
> > > kernel with an accurate device tree. (Though one may
> > > equally well argue that it would be nice to avoid having
> > > to customize the device tree for every feature-flavor of
> > > a processor, especially if this depends on how it's
> > > initialized.)
> > 
> > Nokia X-Loader is closed source and signed. So we cannot
> > modify it. And it is responsible for configuring L3/L4
> > firewall.
> > 
> > Year ago it was possible to find on internet signed X-Loader
> > for N900 which enable omap aes support (for testing purpose
> > together with open source linux kernel modules), but it is
> > unofficial and I think there only too few people who
> > flashed it into N900 nand. If somebody needs binaries I
> > have backup all of them.
> > 
> > More info about that aes enabled X-Loader:
> > http://maemo.org/community/maemo-developers/n900_aes_and_sha
> > 1-md5_hw_acceleration_drivers/
> > 
> > Majority of users use only official X-Loader which does not
> > enable aes support so we cannot enable kernel modules (cause
> > crashes). And also we cannot force users to flash some
> > unofficial binary into their device...
> 
> BTW... it would be interesting to know... are you doing some
> heavy crypto processing on N900? Are the accelerated drivers
> faster than non-accelerated ones? Because the link above says
> they are slower...
> 
> # Eric Wheeler
> # ...
> # Hey guys, I have omap-aes compiled for my kernel and appears
> to be # working.
> #
> # I do not understand why non-accelerated software-crypto is
> faster than # the omap-aes hardware acceleration:
> #
> # mmcblk0 onboard 32GB: read=21.76MB/s write=12.97MB/s
> # aes_generic crypto: read= 8.47 write= 5.54
> # omap-aes hw crypto: read= 6.31 write= 5.45
> #
> # mmcblk1 uSD 16GB Class 10: read=16.05MB/s write=16.47MB/s
> # aes_generic crypto: read= 7.96 write= 7.43
> # omap-aes hw crypto: read= 6.67 write= 7.18
> 
> Best regards,
> 									Pavel

Also depends on CPU usage. Same as there was preview of theora 
decoder. One neon optimized running at arm core provided better 
fps, but used 99%. Another implementation which used DSP core 
provided lower fps, but enough for watching videos and did not 
used full CPU usage...

-- 
Pali Rohár
pali.rohar@gmail.com

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