> -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Juha Yrjölä > Sent: Wednesday, January 21, 2009 10:54 PM > To: [email protected] > Subject: [PATCH] ARM OMAP: Fix race in OMAP2/3 DMA IRQ handling > > CSR must be cleared before invoking the callback. > > If the callback function starts a new, fast DMA transfer on the same > channel, the completion status might lost if CSR is cleared after > the callback invocation. > > Signed-off-by: Juha Yrjola <[email protected]> > --- > arch/arm/plat-omap/dma.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c > index 8e6475d..265351b 100755 > --- a/arch/arm/plat-omap/dma.c > +++ b/arch/arm/plat-omap/dma.c > @@ -1898,11 +1898,11 @@ static int omap2_dma_handle_ch(int ch) > status = dma_read(CSR(ch)); > } > > + dma_write(status, CSR(ch)); This is not necessary. Refers line "dma_write(OMAP2_DMA_CSR_CLEAR_MASK, CSR(ch));" just above.
It will any way do the job of clearing. In a way, clear done after the callback has no effect since the status reg and global IRQ_enable for the particular channel is already disabled before that. > + > if (likely(dma_chan[ch].callback != NULL)) > dma_chan[ch].callback(ch, status, dma_chan[ch].data); > > - dma_write(status, CSR(ch)); > - > return 0; > } > > -- So dma library is safe from the problem you have described. > > -- > 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 > Regards, Santosh -- 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
