On Thu, 17 Jun 2021 at 10:36, nicolas saenz julienne <nsa...@kernel.org> wrote: > Frankly I don't know if there is a better way. IIRC opensuse and downstream > use > DT overlays to cater for this limitation. It seems reasonable to bump the > value. But it'll be in detriment of users that don't care much for graphical > interfaces. Nonetheless, I'm not familiar with how DRM handles CMA/DMA memory. > So let me have a look at it. Maybe there is a SW fix. At first glance I'm > surprised they can't defer to normal page allocations when CMA isn't capable > of > honoring the request (like the dma code does).
DMA transfers can be split into multiple transactions at the cost of being a bit slower. But there isn't a fallback for graphics buffers; you can't display a quarter of a screen at a time. If the hardware did support buffers being backed by multiple discontiguous pages, then it wouldn't need CMA in the first place ... Cheers, Daniel
