On 29-11-2018 13:03, David Laight wrote: > From: Jose Abreu [mailto:jose.abreu@xxxxxxxxxxxx] >> On 29-11-2018 12:47, David Laight wrote: >>> From: Jose Abreu >>>> Sent: 29 November 2018 12:42 >>>> >>>> Some ARC CPU's do not support unaligned loads/stores. Currently, generic >>>> implementation of reads{b/w/l}()/writes{b/w/l}() is being used with ARC. >>>> This can lead to misfunction of some drivers as generic functions do a >>>> plain dereference of a pointer that can be unaligned. >>>> >>>> Let's use {get/put}_unaligned() helper instead of plain dereference of >>>> pointer in order to fix this. >>> Is it worth adding a check for the pointer being aligned? >> We could but then we would need to know which CPU version is >> currently running because some ARC processors support unaligned >> accesses. > Eh? > If the CPU supports unaligned accesses you could patch the code > to do unaligned accesses. *Some* ARC CPU versions support unaligned memory access. The one we tested this on does not support unaligned accesses. > > I was thinking of the (probably likely) case where the pointer is > actually aligned. > An extra check for ((pointer) & 3) is almost certainly a 'win' > over the byte accesses and shift/mask/or use by get/put_unaligned(). > > The IO accesses probably dominate making more complex optimisations > less likely to have any benefit. > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) _______________________________________________ linux-snps-arc mailing list linux-snps-arc@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/linux-snps-arc
