[Interest] [linux] QtCore behaviour w/o system init

[Jason H]

Agreed. In my experience NAND flash is slow.



________________________________
 From: Mandeep Sandhu <mandeepsandhu.chd at gmail.com>
To: Christian Gagneraud <chgans at gna.org> 
Cc: "interest at qt-project.org" <interest at qt-project.org> 
Sent: Monday, September 16, 2013 12:53 AM
Subject: Re: [Interest] [linux] QtCore behaviour w/o system init
 


Actually, I don't k now yet, but right know a good candidate for this

particular project is the SAMA5D3 by Atmel (the only Cortex A5 on the
>market) [1], other candidates on the radar are TI AM35 (beaglebone) or
>43 (?) and Freescale i.mx6 to name a few. I have a very, very strong
>power consumption requirement.
>
>I don't have access to SSD but I will likely only have access to "raw"
>NAND flah.
>

Also, choose your FS carefully. UBIFS (fastest, I think) or YAFFS2 are decently fast, JFFS2 is slow.

 

>>
>> I would try booting a minimal kernel that you compiled yourself ('make
>> xmenuconfig'), compiling Qt statically into your application (This will
>> result in a several MB binary which I would put into your initram fs. I
>> think the most time spent will be just reading the image.
>
>The idea is to get rid of the initram fs, it takes time to the
>bootloader to load it, the XIP kernel (eXecute In Place) is there too to
>help reduce load time, as the bootloader doesn't even have to load the
>kernel.
>I do agree that it will have to be balanced: NAND execution/access time
>(read: read time) vs the speed of loading the same quantity of data from
>NAND to RAM (likely SDDR2, maybe SDDR3) + RAM execution/access time.
>

With XIP you'd normally use a NOR flash because of it's higher read speeds. You cou8ld also try using a uncompressed kernel image, though at the cost of size.


Some more info here:
http://elinux.org/Kernel_XIP


Also have a look at the "Boot to Qt" project. One of the hardware used was a beaglebone:
http://blog.qt.digia.com/blog/2013/08/15/boot-to-qt-on-embedded-android-and-linux-technology-preview-2-released/


HTH,

-mandeep


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