On Thu, Feb 20, 2020 at 10:27 AM Jordan Crouse jcrouse@codeaurora.org wrote:
When CONFIG_INIT_ON_ALLOC_DEFAULT_ON the GMU memory allocator runs afoul of cache coherency issues because it is mapped as write-combine without clearing the cache after it was zeroed.
Rather than duplicate the hacky workaround we use in the GEM allocator for the same reason it turns out that we don't need to have a bespoke memory allocator for the GMU anyway. It uses a flat, global address space and there are only two relatively minor allocations anyway. In short, this is essentially what the DMA API was created for so replace a bunch of memory management code with two calls to allocate and free DMA memory and we're fine.
The only wrinkle is that the memory allocations need to be in a very specific location in the GMU virtual address space so in order to get the iova allocator to do the right thing we need to specify the dma-ranges property in the device tree for the GMU node. Since we've not yet converted the GMU bindings over to YAML two patches quickly turn into four but at the end of it we have at least one bindings file converted to YAML and 99 less lines of code to worry about.
v2: Fix the example bindings for dma-ranges - the third item is the size Pass false to of_dma_configure so that it fails probe if the DMA region is not set up.
This set still works for me as well. Thanks so much! Tested-by: John Stultz john.stultz@linaro.org
thanks -john