* Peter Ujfalusi peter.ujfalusi@ti.com [111031 06:46]:
If the DMA source position has been asked before the first actual data transfer has been done, the CSAC register does not contain valid information. We can identify this situation by checking the CDAC register: CDAC != 0 indicates that the DMA transfer on the channel has been started already. When CDAC == 0 we can not trust the CSAC value since it has not been updated, and can contain random number. Return the start address in case the DMA has not jet started.
Note: The CDAC register has been initialized to 0 at dma_start time.
Signed-off-by: Peter Ujfalusi peter.ujfalusi@ti.com
arch/arm/plat-omap/dma.c | 15 +++++++++++++-- 1 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c index c22217c..38b0d44 100644 --- a/arch/arm/plat-omap/dma.c +++ b/arch/arm/plat-omap/dma.c @@ -1024,12 +1024,23 @@ EXPORT_SYMBOL(omap_set_dma_callback); */ dma_addr_t omap_get_dma_src_pos(int lch) {
u32 cdac; dma_addr_t offset = 0;
if (cpu_is_omap15xx()) offset = p->dma_read(CPC, lch);
- else
offset = p->dma_read(CSAC, lch);
else {
/** CDAC == 0 indicates that the DMA transfer on the channel has* not been started (no data has been transferred so far).* Return the programmed source start address in this case.*/cdac = p->dma_read(CDAC, lch);if (likely(cdac))offset = p->dma_read(CSAC, lch);elseoffset = p->dma_read(CSSA, lch);}
if (IS_DMA_ERRATA(DMA_ERRATA_3_3) && offset == 0) offset = p->dma_read(CSAC, lch);
Should these tests be done only after the errata re-read for both src and dst patches? Otherwise the errata will not be handled?
Tony