Messages in this thread | | | Date | Tue, 17 Jul 2018 16:57:25 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH] dma-mapping: Relax warnings for per-device areas |
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On Sun, Jul 15, 2018 at 02:28:27PM +0200, Fredrik Noring wrote: > Hi Christoph, Robin, > > On Thu, Jul 05, 2018 at 09:36:13PM +0200, Christoph Hellwig wrote: > > > - BUG_ON(!ops); > > > - WARN_ON_ONCE(dev && !dev->coherent_dma_mask); > > > - > > > if (dma_alloc_from_dev_coherent(dev, size, dma_handle, &cpu_addr)) > > > return cpu_addr; > > > > > > + BUG_ON(!ops); > > > + WARN_ON_ONCE(dev && !dev->coherent_dma_mask); > > > > I think doing dma on a device without ops is completely broken no matter > > what you think of it, so I very much disagree with that part of the change. > > > > Also while I don't think not having a dma mask is a good idea even for > > a driver purely using dma coherent pools. If the pools really are on > > the device itself I can see why it might not matter, but for the case > > commonly used on some ARM SOCs where we just reserve memory for certain > > devices from a system pool it very much does matter. > > > > There really is no good excuse to not set a coherent mask in the drivers. > > Here are three other regressions related to the coherent mask WARN_ON_ONCE:
They are a pretty strong indication that yes, you should really set the coherent mask if you ever do coherent allocations..
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