Dell OptiPlex: Resizable BAR and Above 4G Decoding

[omasanori]

The problem you're addressing (if any)

While supported in hardware, Dashero (and the stock firmware) disables Resizable BAR and Above 4G Decoding unconditionally on OptiPlex 7010 and 9010. It decreases the performance with recent graphics cards in some cases.

Describe the solution you'd like

Implementing Resizable BAR and Above 4G Decoding on the platform and adding an option to the setup menu.

Where is the value to a user, and who might that user be?

OptiPlex users with discrete graphics cards will be able to try Resizable BAR to improve the performance. Note that Resizable BAR does not necessarily improve the performance, that is why we need the option in the setup menu.

Describe alternatives you've considered

No response

Additional context

No response

[miczyg1]

It is possible to compile the firmware with enabled ReBARs and expose it in the setup menu:

Configuring ReBAR as above should cause the ReBAR option to be visible in the setup

[omasanori]

Thanks, I will give it a try. Is there any reason not to enable it in official builds, or is it disabled just because no one else want it?

[miczyg1]

Thanks, I will give it a try. Is there any reason not to enable it in official builds, or is it disabled just because no one else want it?

I don't remember why it wasn't enabled in the official builds.

[PerAstraAdDeum]

Thanks, I will give it a try. Is there any reason not to enable it in official builds, or is it disabled just because no one else want it?

I don't remember why it wasn't enabled in the official builds.

I've asked before about ReBAR support on NovaCustom Laptops and from what I remember the reason why this wasn't part of the official builds was because it would require too much testing?

Maybe you could enable the option in the official build but label it as experimental and not thoroughly tested, so users can turn it on if they want to on their own risks?

[miczyg1]

Maybe you could enable the option in the official build but label it as experimental and not thoroughly tested, so users can turn it on if they want to on their own risks?

This options works and is not suitable for experimental label. However, depending on the PCI device population one may end up with unsufficient MMIO space to allocate all resources, which may lead to lack of graphics output (which may seem like a brick). There are too many variables at play here.

Usually when an unexpected thing happen, liek above, one should reset CMOS battery to reset firmware settings. However, Dasharo does not implement that yet IIRC.

[omasanori]

Usually when an unexpected thing happen, [like] above, one should reset CMOS battery to reset firmware settings. However, Dasharo does not implement that yet IIRC.

#687 and #1233