Messages in this thread | | | Subject | Re: [PATCH] mtd: m25p80: make command buffer DMA-safe | From | Artem Bityutskiy <> | Date | Tue, 10 Nov 2009 16:54:07 +0200 |
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On Tue, 2009-11-03 at 11:00 +0100, Johannes Stezenbach wrote: > On Tue, Nov 03, 2009 at 08:36:05AM +0200, Artem Bityutskiy wrote: > > On Wed, 2009-10-28 at 14:21 +0100, Johannes Stezenbach wrote: > > > spi_write() requires the buffer to be DMA-safe, kmalloc() > > > it seperately to ensure this. > > > > Even though it is just 4 or 5 bytes it can do DMA? Does not sound too > > sane to use DMA in that case. Does this patch fix a real error? > > > > I do not know much about SPI, but for me it sounds like there should be > > a method to ask SPI to avoid using DMA, and you should use that method. > > It fixes a real error -- with an out-of-tree driver and ancient kernel. > For the flash read/write case it is used with list-DMA (e.g. write 4 bytes, > read 64KB). There are extensive comments in include/linux/spi/spi.h > which document the DMA-safe requirement of the buffers.
Pushed to my l2-mtd-2.6 tree, thanks.
-- Best Regards, Artem Bityutskiy (Артём Битюцкий)
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