* Peter Ujfalusi <peter.ujfalusi@xxxxxx> [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@xxxxxx>
> ---
> 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?
Tony
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