Hi David, On Mon, 2015-06-22 at 09:43 +0300, Alexey Brodkin wrote: > Hi David, > > On Sun, 2015-06-21 at 09:29 -0700, David Miller wrote: > > From: Alexey Brodkin <alexey.brod...@synopsys.com> > > Date: Tue, 16 Jun 2015 20:40:41 +0300 > > > > > Current implementtion of descriptor init procedure only takes > > > care > > > about > > > ownership flag. While it is perfectly possible to have underlying > > > > > > memory > > > filled with garbage on boot or driver installation. > > > > > > And randomly set flags in non-zeroed des0 and des1 fields may > > > lead > > > to > > > unpredictable behavior of the GMAC DMA block. > > > > > > Solution to this problem is as simple as explicit zeroing of both > > > > > > des0 > > > and des1 fields of all buffer descriptors. > > > > > > Signed-off-by: Alexey Brodkin <abrod...@synopsys.com> > > > > If you need the memory zero initialized, use dma_zalloc_coherent(). > > Indeed usage of dma_zalloc_coherent() will resolve observed issue. > But since buffer descriptors are reused extensively I would say that > explicit zeroing of fields with flags is useful. Probably I need to > add > this clarification in commit message. > > And then if we do that explicit zeroing of flags and other fields > which > hold data size and addresses of data buffer and the next descriptor > in > chain are all get set later we may not care about allocation of > zeroed > memory.
I'm wondering if my comment makes sense and should I just change commit message or you'd prefer to still use dma_zalloc_coherent() during driver probe? -Alexey-- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
