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SubjectRe: [RFC PATCH 2/2 -mm] RapidIO: TSI721 Add DMA Engine support
On Mon, 3 Oct 2011 10:53:45 -0700
"Bounine, Alexandre" <Alexandre.Bounine@idt.com> wrote:

> > > + memset(bd_ptr, 0, bd_num * sizeof(struct tsi721_dma_desc));
> > > +
> > > + dev_dbg(dev, "DMA descriptors @ %p (phys = %llx)\n",
> > > + bd_ptr, (unsigned long long)bd_phys);
> > > +
> > > + /* Allocate space for descriptor status FIFO */
> > > + sts_size = (bd_num >= TSI721_DMA_MINSTSSZ) ?
> > > + bd_num : TSI721_DMA_MINSTSSZ;
> > > + sts_size = roundup_pow_of_two(sts_size);
> > > + sts_ptr = dma_alloc_coherent(dev,
> > > + sts_size * sizeof(struct
> tsi721_dma_sts),
> > > + &sts_phys, GFP_KERNEL);
> > > + if (!sts_ptr) {
> > > + /* Free space allocated for DMA descriptors */
> > > + dma_free_coherent(dev,
> > > + bd_num * sizeof(struct
> tsi721_dma_desc),
> > > + bd_ptr, bd_phys);
> > > + chan->bd_base = NULL;
> > > + return -ENOMEM;
> > > + }
> > > +
> > > + chan->sts_phys = sts_phys;
> > > + chan->sts_base = sts_ptr;
> > > + chan->sts_size = sts_size;
> > > +
> > > + memset(sts_ptr, 0, sts_size);
> >
> > You meant
>
> I really need it here. That status block tracks progress by keeping
> non-zero addresses of processed descriptors.

Confused. Are you saying that the use of "sts_size" there was
intentional?

> >
> > --- a/drivers/rapidio/devices/tsi721.c~rapidio-tsi721-add-dma-engine-
> > support-fix
> > +++ a/drivers/rapidio/devices/tsi721.c
> > @@ -1006,7 +1006,7 @@ static int tsi721_bdma_maint_init(struct
> > priv->mdma.sts_base = sts_ptr;
> > priv->mdma.sts_size = sts_size;
> >
> > - memset(sts_ptr, 0, sts_size);
> > + memset(sts_ptr, 0, sts_size * sizeof(struct tsi721_dma_sts));
> >
> > dev_dbg(&priv->pdev->dev,
> > "desc status FIFO @ %p (phys = %llx) size=0x%x\n",
> >
> > However that's at least two instances where you wanted a
> > dma_zalloc_coherent(). How's about we give ourselves one?
>
> Does this mean that I am on hook for it as a "most frequent user"?

No, it can be used all over the place: drivers/net/irda/w83977af_ir.c,
drivers/scsi/bnx2fc/bnx2fc_tgt.c,
drivers/net/wireless/rt2x00/rt2x00pci.c,
drivers/crypto/amcc/crypto4xx_core.c and many nmore.




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