On Wed, Oct 27, 2010 at 01:52:55AM +0200, Ilya Yanok wrote: > While testing mpc512x-dma driver with dmatest module I've found that > I can hang the mpc512x-dma issueing request from multiple threads to > the single channel. > (insmod dmatest.ko max_channels=1 threads_per_chan=16) > After investingating this case I've managed to find that this happens > if and only if we have more than one quequed requests. > In this case the driver tries to make use of hardware scatter/gather > functionality. I've found two problems with scatter/gather: > 1. When TCD is copied form RAM to the TCD register space with memcpy_io() > e_sg bit eventually gets cleared. This results in only first TCD being > executed. I've added setting of e_sg bit excplicitly in the TCD registers. > BTW, what is the correct way to do this? (How can I use setbits with bitfield > structure?) After that hardware loads consecutive TCDs and we hit the > second issue. > 2. Existing code clears int_maj bit in the last TCD so we never get > an interrupt on transfefr completion. > > With these fixes my tests with many threads of single channel succeed but > tests that use many channels simultaneously still don't work reliable. > > Signed-off-by: Ilya Yanok <ya...@emcraft.com> > Cc: Piotr Ziecik <ko...@semihalf.com>
Merged for -next, thanks. g. > --- > drivers/dma/mpc512x_dma.c | 4 +++- > 1 files changed, 3 insertions(+), 1 deletions(-) > > diff --git a/drivers/dma/mpc512x_dma.c b/drivers/dma/mpc512x_dma.c > index 4e9cbf3..1bc04aa 100644 > --- a/drivers/dma/mpc512x_dma.c > +++ b/drivers/dma/mpc512x_dma.c > @@ -252,11 +252,13 @@ static void mpc_dma_execute(struct mpc_dma_chan *mchan) > prev = mdesc; > } > > - prev->tcd->start = 0; > prev->tcd->int_maj = 1; > > /* Send first descriptor in chain into hardware */ > memcpy_toio(&mdma->tcd[cid], first->tcd, sizeof(struct mpc_dma_tcd)); > + > + if (first != prev) > + mdma->tcd[cid].e_sg = 1; > out_8(&mdma->regs->dmassrt, cid); > } > > -- > 1.7.2.3 > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
