Messages in this thread | | | Date | Fri, 23 Jun 2006 02:08:50 +0800 | From | "Antonino A. Daplas" <> | Subject | Re: CONFIG_VGACON_SOFT_SCROLLBACK crashes 2.6.17 |
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Al Boldi wrote: > Antonino A. Daplas wrote: >> Al Boldi wrote: >>> Antonino A. Daplas wrote: >>>> Al Boldi wrote: > >> Anyway, can you try the patch below. It's a debugging patch and >> it will slow down the console. > > Yes, that did the trick, although it screws-up concurrent console access. > > What is surprising though, is that SOFT_SCROLLBACK is supposed to slow the > console down. It actually looks that it speeds things up, albeit at higher > CPU cost, by buffering screen updates. > > This maybe hardware related. This machine has an onboard VIA/S3 UniChrome > chip, so I am thinking the CPU is dumping too fast for the chip to sync. >
That's what I thought too. But adding delays to the screen accessors is not the correct fix. The screen buffer accessors, scr_readw() and scr_writew() make assumptions that are not correct in all cases, that the screenbuffer is either in system RAM or video RAM, never in both. (vgacon's screenbuffer is video RAM while the rest of the console drivers have it in system RAM. But you can have vgacon and fbcon compiled at the same time, for example, and this basically screws up the screen accessors, especially in non-x86 archs.)
So a revamp of vgacon may be necessary, by placing the screen buffer in system RAM. This will entail a lot of work, so the revamp will take some time.
>> If the system hang disappears, remove the line >> >> while (i--); > > Hangs again.
I was hoping that's it's the memcpy() that's buggy when the source/destination is video RAM. That would be an easy fix, but it seems I'm out of luck here.
> >>> BTW, is there any chance to patch your savagefb to support VIA/S3 >>> UniChrome? >> If someone posts a patch to lkml or fbdev-devel, why not? But a separate >> driver is probably better as the 2 are very different. > > VIA has a separate driver, couldn't this be merged with mainline?
Sure, as long as it's GPL-compatible, properly written, and correctly Signed-off.
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