Messages in this thread Patch in this message | | | Subject | Re: [PATCH] dmaengine: pl330: Fix linker error "undefined reference to `__aeabi_uldivmod'" | From | Joe Perches <> | Date | Thu, 13 Nov 2014 09:02:52 -0800 |
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On Thu, 2014-11-13 at 16:27 +0000, Jon Medhurst (Tixy) wrote: > 32-bit ARM kernels may have a 64-bit dma_addr_t but have no > implementation of the compiler helper for 64-bit unsigned division, > therefore the use of the modulo operator in pl330_prep_dma_memcpy causes > the link error "undefined reference to `__aeabi_uldivmod'" > > As the burst value is always a power of two we can fix the problem, and > make the code more efficient, by replacing "% burst" with "& (burst-1)". > > Reported-by: kbuild test robot <fengguang.wu@intel.com> > Signed-off-by: Jon Medhurst <tixy@linaro.org> > --- > > Vinod. I haven't added a 'Fixes:' line because I was unsure if the patch > in linux-next is part of a stable branch or if the SHA1 might change > before hitting mainline. If it stable then the line should be... > > Fixes: 63369d0a96dc ("dmaengine: pl330: Align DMA memcpy operations to MFIFO width") > > > drivers/dma/pl330.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c > index 38c9617..52c4c62 100644 > --- a/drivers/dma/pl330.c > +++ b/drivers/dma/pl330.c > @@ -2464,11 +2464,8 @@ pl330_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dst, > * parameters because our DMA programming algorithm doesn't cope with > * transfers which straddle an entry in the DMA device's MFIFO. > */ > - while (burst > 1) { > - if (!((src | dst | len) % burst)) > - break; > + while ((src | dst | len) & (burst - 1)) > burst /= 2; > - }
Maybe something like:
div = ffs(src | dst | len); if (burst > 1 && div) burst >>= div;
?
dunno if dma_addr_t src or dst can ever be a 64 bit value for AMBA or not. If so, the ffs would need to be different.
Maybe:
if (sizeof(dma_addr_t) == sizeof(u64)) div = __ffs64(src | dst | len); else div = ffs(src | dst | len); if (burst > 1 && div) burst >>= div;
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