Virtualization - Feb 2023 - [PATCH 17/17] drm/cirrus: Use VGA macro constants to unblank

On Thu, Feb 16, 2023 at 01:03:02PM +0100, Thomas Zimmermann
wrote:
> Hi,
> 
> thanks for taking a look at the patches.
> 
> Am 16.02.23 um 12:33 schrieb Gerd Hoffmann:
> > On Wed, Feb 15, 2023 at 05:15:17PM +0100, Thomas Zimmermann wrote:
> >> Set the VGA bit for unblanking with macro constants instead of
magic
> >> values. No functional changes.
> > 
> > blank/unblank should work simliar to bochs (see commit 250e743915d4),
> > that is maybe a nice thing to add of you modernize the driver anyway.
> Yeah, it's the VGA PAS field. [1] But is it really called blanking? PAS
> controls palette access, but blanking is sounds more like DPMS.
Why aren't people just using the normal way of flipping the
screen off bit in sequencer register 01?

> 
> The PAS setting is actually part of the primary plane, so it's current 
> location in the CRTC code is misleading. I didn't want to change the 
> driver logic too much, but I guess I'll fix that in the next iteration.
> 
> Best regards
> Thomas
> 
> [1] 
>
https://web.stanford.edu/class/cs140/projects/pintos/specs/freevga/vga/attrreg.htm#3C0
> 
> > 
> > take care,
> >    Gerd
> > 
> 
> -- 
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 N?rnberg, Germany
> (HRB 36809, AG N?rnberg)
> Gesch?ftsf?hrer: Ivo Totev



-- 
Ville Syrj?l?
Intel

On Thu, Feb 16, 2023 at 02:52:51PM +0200, Ville Syrj?l?
wrote:
> On Thu, Feb 16, 2023 at 01:03:02PM +0100, Thomas Zimmermann wrote:
> > Hi,
> > 
> > thanks for taking a look at the patches.
> > 
> > Am 16.02.23 um 12:33 schrieb Gerd Hoffmann:
> > > On Wed, Feb 15, 2023 at 05:15:17PM +0100, Thomas Zimmermann
wrote:
> > >> Set the VGA bit for unblanking with macro constants instead
of magic
> > >> values. No functional changes.
> > > 
> > > blank/unblank should work simliar to bochs (see commit
250e743915d4),
> > > that is maybe a nice thing to add of you modernize the driver
anyway.
> > Yeah, it's the VGA PAS field. [1] But is it really called
blanking? PAS
> > controls palette access, but blanking is sounds more like DPMS.
> 
> Why aren't people just using the normal way of flipping the
> screen off bit in sequencer register 01?
qemu vga emulation doesn't check that bit ...

take care,
  Gerd

Hi

Am 16.02.23 um 13:52 schrieb Ville Syrj?l?:
> On Thu, Feb 16, 2023 at 01:03:02PM +0100, Thomas Zimmermann wrote:
>> Hi,
>>
>> thanks for taking a look at the patches.
>>
>> Am 16.02.23 um 12:33 schrieb Gerd Hoffmann:
>>> On Wed, Feb 15, 2023 at 05:15:17PM +0100, Thomas Zimmermann wrote:
>>>> Set the VGA bit for unblanking with macro constants instead of
magic
>>>> values. No functional changes.
>>>
>>> blank/unblank should work simliar to bochs (see commit
250e743915d4),
>>> that is maybe a nice thing to add of you modernize the driver
anyway.
>> Yeah, it's the VGA PAS field. [1] But is it really called blanking?
PAS
>> controls palette access, but blanking is sounds more like DPMS.
> 
> Why aren't people just using the normal way of flipping the
> screen off bit in sequencer register 01?
Setting the SD bit in SR01 isn't a bad idea. We can do this as part of 
enabling/disabling the plane.

But for PAS, we don't have a choice. It's one of the bazillion obscure 
VGA settings and (according to a comment in the source code) we need to 
update it for compatibility.

Best regards
Thomas
> 
> 
>>
>> The PAS setting is actually part of the primary plane, so it's
current
>> location in the CRTC code is misleading. I didn't want to change
the
>> driver logic too much, but I guess I'll fix that in the next
iteration.
>>
>> Best regards
>> Thomas
>>
>> [1]
>>
https://web.stanford.edu/class/cs140/projects/pintos/specs/freevga/vga/attrreg.htm#3C0
>>
>>>
>>> take care,
>>>     Gerd
>>>
>>
>> -- 
>> Thomas Zimmermann
>> Graphics Driver Developer
>> SUSE Software Solutions Germany GmbH
>> Maxfeldstr. 5, 90409 N?rnberg, Germany
>> (HRB 36809, AG N?rnberg)
>> Gesch?ftsf?hrer: Ivo Totev
> 
> 
> 
> 
-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 N?rnberg, Germany
(HRB 36809, AG N?rnberg)
Gesch?ftsf?hrer: Ivo Totev
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