* Tony Lindgren <[email protected]> [111103 13:53]: > * Peter Ujfalusi <[email protected]> [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 <[email protected]> > > --- > > 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); > > + else > > + offset = 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?
Also, please Cc linux-arm-kernel list too so I don't have to repost :) Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
