On Thursday, August 26, 2010 08:49:09 pm Russell King - ARM Linux wrote: > On Thu, Aug 26, 2010 at 06:51:48PM +0900, FUJITA Tomonori wrote: > > On Thu, 26 Aug 2010 11:45:58 +0200 (CEST) > > Guennadi Liakhovetski <g.liakhovetski@xxxxxx> wrote: > > > > > On Thu, 26 Aug 2010, FUJITA Tomonori wrote: > > > > > > > Why can't you revert a commit that causes the regression? > > > > > > See this reply, and the complete thread too. > > > > > > http://marc.info/?l=linux-sh&m=128130485208262&w=2 > > > > > > > The related DMA API wasn't changed in 2.6.36-rc1. The DMA API is not > > > > responsible for the regression. And the patchset even exnteds the > > > > definition of the DMA API (dma_declare_coherent_memory). Such change > > > > shouldn't applied after rc1. I think that DMA-API.txt says that > > > > dma_declare_coherent_memory() handles coherent memory for a particular > > > > device. It's not for the API that reserves coherent memory that can be > > > > used for any device for a single device. > > > > > > Anyway, we need a way to fix the regression. > > > > Needs to find a different way. > > No. ioremap on memory mapped by the kernel is just plain not permitted > with ARMv6 and ARMv7 architectures. Hi Russell, Just because ioremap on memory mapped by the kernel is just plain not permitted I have proposed a new pair of functions: dma_reserve_coherent_memory()/dma_free_reserved_memory() http://lkml.org/lkml/2010/8/19/200 but it is not quite well accepted from the community. What is your opinion? Thanks, Marin Mitov > > It's not something you can say "oh, need to find another way" because there > is _no_ software solution to having physical regions mapped multiple times > with different attributes. It's an architectural restriction. > > We can't unmap the kernel's memory mapping either, as I've already explained > several times this month - and I'm getting frustrated at having to keep > on explaining that point. > > Just accept the plain fact that multiple mappings of the same physical > regions have become illegal. > > What we need is another alternative other than using ioremap on memory > already mapped by the kernel - eg, by reserving a certain chunk of > memory for this purpose at boot time which his _never_ mapped by the > kernel, except via ioremap. > -- > To unsubscribe from this list: send the line "unsubscribe linux-media" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
