Can someone check this? On Mon, Apr 20, 2020 at 9:24 PM Ajay kumar <ajaynumb@xxxxxxxxx> wrote: > > Hi All, > > I have an IOMMU master which has limitations as mentioned below: > 1) The IOMMU master internally executes a firmware, and the firmware memory > is allocated by the same master driver. > The firmware buffer address should be of the lowest range than other address > allocated by the device, or in other words, all the remaining buffer addresses > should always be in a higher range than the firmware address. > 2) None of the buffer addresses should go beyond 0xC000_0000 > > example: > If firmware buffer address is buf_fw = 0x8000_5000; > All other addresses given to the device should be greater than > (0x8000_5000 + firmware size) and less than 0xC000_0000 > > Currently, this is being handled with one of the below hacks: > 1) By keeping dma_mask in lower range while allocating firmware buffer, > and then increasing the dma_mask to higher range for other buffers. > 2) By reserving IOVA for firmware at the lowest range and creating direct mappings for the same. > > I want to know if there is a better way this can be handled with current framework, > or if anybody is facing similar problems with their devices, > please share how it is taken care. > > I also think there should be some way the masters can specify the IOVA > range they want to limit to for current allocation. > Something like a new iommu_ops callback like below: > limit_iova_alloc_range(dev, iova_start, iova_end) > > And, in my driver, the sequence will be: > limit_iova_alloc_range(dev, 0x0000_0000, 0x1000_0000); /* via helpers */ > alloc( ) firmware buffer using DMA API > limit_iova_alloc_range(dev, 0x1000_0000, 0xC000_0000); /* via helpers */ > alloc( ) other buffers using DMA API > > Thanks, > Ajay Kumar
