On Wed, Feb 20, 2019 at 1:29 AM Yann Sionneau <ysionneau@xxxxxxxxx> wrote: > > I'm not sure dma_alloc_coherent() should return zeroed out memory. > > I'm pretty sure it does not. > > mips arch seems to memset it to 0, but not all arch do that. > It is definitely the semantics in latest kernel code, see e.g. here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.0-rc7&id=dfd32cad146e3624970eee9329e99d2c6ef751b3 As for Barebox, currently there are three architectures that select HAS_DMA to indicate that they implement said DMA functions: MIPS, ARM and ARM64. As you mentioned before MIPS already does the right thing and a series to do the same on ARM/ARM64 was recently merged into "next" as well, specifically this patch: https://git.pengutronix.de/cgit/barebox/commit/arch/arm/cpu/mmu-common.c?h=next&id=7179471fd7651e8ddd7758d2c3c94928421e5493 I think this should cover all of the bases as far as xHCI is concerned. Having looked at it againg, the only two "non-zeroing" cases that I can see in the codebase are: 1. Nios II which, AFAICT, only uses DMA functions in drivers/net/altera_tse.c. Since it doesn't select HAS_DMA and is pretty self-contained, I don't think there's any reason to worry about leaving it as it is. 2. No MMU case on ARM/ARM64, I doubt there are many users of that combination, but it is definitely something that should be fixed. I'll submit a separate series for that. Thanks, Andrey Smirnov > On 2/20/19 8:29 AM, Andrey Smirnov wrote: > > Memory returned by dma_alloc_coherent() should already be zeroed > > out, so there's no need to do this explicitly. > > > > Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx> > > --- > > drivers/usb/host/xhci-hcd.c | 2 -- > > 1 file changed, 2 deletions(-) > > > > diff --git a/drivers/usb/host/xhci-hcd.c b/drivers/usb/host/xhci-hcd.c > > index 7cfd74de4..7106a5637 100644 > > --- a/drivers/usb/host/xhci-hcd.c > > +++ b/drivers/usb/host/xhci-hcd.c > > @@ -445,7 +445,6 @@ static struct xhci_virtual_device *xhci_alloc_virtdev(struct xhci_hcd *xhci, > > > > vdev->dma_size = sz_ictx + sz_dctx; > > p = vdev->dma = dma_alloc_coherent(vdev->dma_size, DMA_ADDRESS_BROKEN); > > - memset(vdev->dma, 0, vdev->dma_size); > > > > vdev->out_ctx = p; p += sz_dctx; > > vdev->in_ctx = p; p += sz_ictx; > > @@ -1225,7 +1224,6 @@ static void xhci_dma_alloc(struct xhci_hcd *xhci) > > xhci->dma_size += num_ep * sz_ep; > > > > p = xhci->dma = dma_alloc_coherent(xhci->dma_size, DMA_ADDRESS_BROKEN); > > - memset(xhci->dma, 0, xhci->dma_size); > > > > xhci->sp = p; p += sz_sp; > > xhci->dcbaa = p; p += sz_dca; _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
