* PCIE resetting graphic card
@ 2013-07-12 2:04 Dave Young
2013-07-12 2:39 ` Takao Indoh
0 siblings, 1 reply; 3+ messages in thread
From: Dave Young @ 2013-07-12 2:04 UTC (permalink / raw)
To: Takao Indoh; +Cc: airlied, Vivek Goyal, Baoquan He, Chao Wang, lkml
Hi, Takao
I know you are working on the PCIE resetting patches for the iommu kdump
issue.
You explicitly excluded the graphic card in your patch. I have some
questions about this. Why can't we reset the graphic card like other
pcie devices?
We have problems, if 1st kernel is in kms mode kdump kernel will have no
chance to switch back to VGA console. There's no serial port on most of
recent laptops thus it's difficult to debug kdump issue.
So if we can reset graphic card as well, and if it works I wonder if the
2nd kdump kernel can use vga console with nomodeset?
--
Thanks
Dave
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: PCIE resetting graphic card
2013-07-12 2:04 PCIE resetting graphic card Dave Young
@ 2013-07-12 2:39 ` Takao Indoh
2013-07-12 2:52 ` Dave Young
0 siblings, 1 reply; 3+ messages in thread
From: Takao Indoh @ 2013-07-12 2:39 UTC (permalink / raw)
To: dyoung; +Cc: airlied, vgoyal, bhe, chaowang, linux-kernel, ishii.hironobu
Hi Dave,
(2013/07/12 11:04), Dave Young wrote:
> Hi, Takao
>
> I know you are working on the PCIE resetting patches for the iommu kdump
> issue.
>
> You explicitly excluded the graphic card in your patch. I have some
> questions about this. Why can't we reset the graphic card like other
> pcie devices?
As far as I tested, the monitor blacks out after video controller is
reset, and we cannot know what's going on. So, for now display device is
not reset in my patch.
I'm not sure what we need to do to recover graphic card after its reset,
but my colleague said that we need to run BIOS code to get back legacy
VGA mode after reset. It seems not to be easy:-(
Maybe this document is helpful to do this.
http://www.coreboot.org/images/2/2b/Vgabios.pdf
Thanks,
Takao Indoh
>
> We have problems, if 1st kernel is in kms mode kdump kernel will have no
> chance to switch back to VGA console. There's no serial port on most of
> recent laptops thus it's difficult to debug kdump issue.
>
> So if we can reset graphic card as well, and if it works I wonder if the
> 2nd kdump kernel can use vga console with nomodeset?
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: PCIE resetting graphic card
2013-07-12 2:39 ` Takao Indoh
@ 2013-07-12 2:52 ` Dave Young
0 siblings, 0 replies; 3+ messages in thread
From: Dave Young @ 2013-07-12 2:52 UTC (permalink / raw)
To: Takao Indoh; +Cc: airlied, vgoyal, bhe, chaowang, linux-kernel, ishii.hironobu
Hi, Takao
On 07/12/2013 10:39 AM, Takao Indoh wrote:
> Hi Dave,
>
> (2013/07/12 11:04), Dave Young wrote:
>> Hi, Takao
>>
>> I know you are working on the PCIE resetting patches for the iommu kdump
>> issue.
>>
>> You explicitly excluded the graphic card in your patch. I have some
>> questions about this. Why can't we reset the graphic card like other
>> pcie devices?
>
> As far as I tested, the monitor blacks out after video controller is
> reset, and we cannot know what's going on. So, for now display device is
> not reset in my patch.
>
> I'm not sure what we need to do to recover graphic card after its reset,
> but my colleague said that we need to run BIOS code to get back legacy
> VGA mode after reset. It seems not to be easy:-(
>
> Maybe this document is helpful to do this.
> http://www.coreboot.org/images/2/2b/Vgabios.pdf
Thanks for quick response and the info about vgabios. It's awkward that
we can not switch back to VGA mode.
--
Thanks
Dave
^ permalink raw reply [flat|nested] 3+ messages in thread
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