On Tue, 12 May 2020 at 06:28, Alex Deucher alexdeucher@gmail.com wrote:
On Mon, May 11, 2020 at 4:22 PM Al Dunsmuir al.dunsmuir@sympatico.ca wrote:
On Monday, May 11, 2020, 1:17:19 PM, "Christian König" wrote:
Hi guys,
Well let's face it AGP is a total headache to maintain and dead for at least 10+ years.
We have a lot of x86 specific stuff in the architecture independent graphics memory management to get the caching right, abusing the DMA API on multiple occasions, need to distinct between AGP and driver specific page tables etc etc...
So the idea here is to just go ahead and remove the support from Radeon and Nouveau and then drop the necessary code from TTM.
For Radeon this means that we just switch over to the driver specific page tables and everything should more or less continue to work.
For Nouveau I'm not 100% sure, but from the code it of hand looks like we can do it similar to Radeon.
Please comment what you think about this.
Regards, Christian.
Christian,
I would respectfully ask that this change be rejected.
I'm currently an end user on both Intel (32-bit and 64-bit) and PPC (Macs, IBM Power - BE and LE).
Linux is not just used for modern hardware. There is also a subset of the user base that uses it for what is often termed retro-computing. No it's not commercial usage, but no one can seriously claim that that Linux is for business only.
Often the old hardware is built far batter than the modern junk, and will continue to run for years to come. This group of folks either has existing hardware they wish to continue to use, or are acquiring the same because they are tired of generic locked-down hardware.
A significant percentage of the video hardware that falls in the retro category uses the AGP video bus. Removing that support for those cases where it works would severely limit performance and in some cases functionality. This can mean the difference between being able to run an application, or having it fail.
Note there is no loss of functionality here, at least on radeon hardware. It just comes down to which MMU gets used for access to system memory, the AGP MMU on the chipset or the MMU built into the GPU. On powerpc hardware, AGP has been particularly unstable, and AGP has been disabled by default on radeon on powerpc for years now. In fact, this will probably make older hardware more reliable as it takes AGP out of the equation.
From memory there is quite a loss in speed though, like pretty severe.
The radeon PCI GART has a single slot TLB, if memory serves.
I think this is going to be a hard sell at this stage, I'm guessing users will crawl out of the woodwork, I'm sure with 2 hours after I'm able to access the office, I can boot the 865 AGP box with an rv350 in it on a modern distro.
Maybe we can find some way to compartmentalise AGP further?
Dave.