[Lenny400] [Letux-kernel] JZ4730/Minibook framebuffer driver updates
H. Nikolaus Schaller
hns at goldelico.com
Sun Sep 10 20:55:15 CEST 2017
> Am 10.09.2017 um 19:55 schrieb Daniel Glöckner <daniel-gl at gmx.net>:
> On Sun, Sep 10, 2017 at 07:31:44PM +0200, H. Nikolaus Schaller wrote:
>> Let's think about where limitations could be...
>> 1. the total card size may be limited by file system but FAT and ext can
>> handle big file systems
>> 2. the raw MMC driver treats the card as single big file with partitions
>> - but there I am not aware of limits
>> 3. the partition manager might ot be able to handle big partitions - but
>> this works well on ARM - why should MIPS be different?
>> 4. there might be a limit in the MMC controller inside the JZ4730 and the
>> raw MMC driver that it can't send big block addresses automatically.
>> It would only a problem if the MMC controller has e.g. a 16 or 24 bit
>> register for block address and there is a "read block" command and
>> everything else is done by DMA. Then, an old controller can never send
>> "extended" addresses going beyond the card's capabilities to the card.
> 5. The U-Boot that we don't dare to replace might be too old to load the
> kernel from an SDHC card.
Ah, yes. That could happen.
But is quite unlikely. There is a first FAT partition which contains the uImage
and that is everything which should be loaded. I'd expect that as long as the
first partition is small enough, U-Boot will even find it on the first sectors
of an SDXC card.
> I've been following the recent activities on this mailing list and I really
> hope it will lead to mainline support for this device. But did I understand
> correctly that all of the work so far has been done without booting the new
I still have to remove dust from my devices (one is still missing) and find
out which ones are still booting from flash with the built-in 2.4 kernel.
Next I have to add the uart interface to watch the boot console.
And before booting the 2.6.24, I have to flash a working old SD card first :)
And then we will see if we can get a mainline kernel running...
Best expectation is that we see
[0.00000] first messages
and then something hangs or emits warnings, errors or kernel panics. Then
printk() becomes our best friend :)
Worst expectation is that we do not see anything after
This is more difficult, but not impossible to debug (even without JTAG). I
had that on the GTA04 several times during our long journey towards latest
But IMHO chances are not thad bad. I looked through Paul's code and although
I did not understand everything and have not compared, he has basically mixed
things from the older 2.6.24 kernel and modern (and tested) jz4740/80 code.
So I'd expect the mix to be 80% correct and less than 20% wrong...
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