RE: [PATCH 1/3] dmaengine: pl330: Set residue in tx_status callback.

[Chanho Park <chanho61.park@samsung.com>]

Hi Dylan,

> -----Original Message-----
> From: dgreid@google.com [mailto:dgreid@google.com] On Behalf Of Dylan
> Reid
> Sent: Wednesday, October 02, 2013 1:34 PM
> To: Chanho Park
> Cc: Padmavathi Venna; linux-samsung-soc@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; padma.kvr@gmail.com; kgene.kim@samsung.com;
> arnd@arndb.de; Sangbeom Kim; vinod.koul@intel.com; Mark Brown; Olof
> Johansson
> Subject: Re: [PATCH 1/3] dmaengine: pl330: Set residue in tx_status
> callback.
> 
> On Thu, Sep 12, 2013 at 4:40 AM, Chanho Park <chanho61.park@samsung.com>
> wrote:
> > Hi Padmavathi,
> >
> >> -----Original Message-----
> >> From: linux-arm-kernel [mailto:linux-arm-kernel-
> >> bounces@lists.infradead.org] On Behalf Of Padmavathi Venna
> >> Sent: Wednesday, September 11, 2013 3:08 PM
> >> To: linux-samsung-soc@vger.kernel.org; linux-arm-
> >> kernel@lists.infradead.org; padma.v@samsung.com; padma.kvr@gmail.com
> >> Cc: kgene.kim@samsung.com; arnd@arndb.de; sbkim73@samsung.com;
> >> vinod.koul@intel.com; broonie@kernel.org; dgreid@chromium.org;
> >> olofj@chromium.org
> >> Subject: [PATCH 1/3] dmaengine: pl330: Set residue in tx_status
> callback.
> >>
> >> From: Dylan Reid <dgreid@chromium.org>
> >>
> >> Fill txstate.residue with the amount of bytes remaining in the
> >> current transfer if the transfer is not complete.  This will be of
> >> particular use to i2s DMA transfers, providing more accurate hw_ptr
> values to ASoC.
> >>
> >> Signed-off-by: Dylan Reid <dgreid@chromium.org>
> >> Reviewed-by: Olof Johansson <olofj@chromium.org>
> >> Signed-off-by: Padmavathi Venna <padma.v@samsung.com>
> >> ---
> >>  drivers/dma/pl330.c |   55
> >> ++++++++++++++++++++++++++++++++++++++++++++++++++-
> >>  1 files changed, 54 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c index
> >> 593827b..7ab9136 100644
> >> --- a/drivers/dma/pl330.c
> >> +++ b/drivers/dma/pl330.c
> >> @@ -2476,11 +2476,64 @@ static void pl330_free_chan_resources(struct
> >> dma_chan *chan)
> >>       spin_unlock_irqrestore(&pch->lock, flags);  }
> >>
> >> +static inline int
> >> +pl330_src_addr_in_desc(struct dma_pl330_desc *desc, unsigned int sar)
> {
> >> +     return ((desc->px.src_addr <= sar) &&
> >> +             (sar <= (desc->px.src_addr + desc->px.bytes))); }
> >> +
> >> +static inline int
> >> +pl330_dst_addr_in_desc(struct dma_pl330_desc *desc, unsigned int dar)
> {
> >> +     return ((desc->px.dst_addr <= dar) &&
> >> +             (dar <= (desc->px.dst_addr + desc->px.bytes))); }
> >> +
> >> +static unsigned int pl330_tx_residue(struct dma_chan *chan) {
> >> +     struct dma_pl330_chan *pch = to_pchan(chan);
> >> +     void __iomem *regs = pch->dmac->pif.base;
> >> +     struct pl330_thread *thrd = pch->pl330_chid;
> >> +     struct dma_pl330_desc *desc;
> >> +     unsigned int sar, dar;
> >> +     unsigned int residue = 0;
> >> +     unsigned long flags;
> >> +
> >> +     sar = readl(regs + SA(thrd->id));
> >> +     dar = readl(regs + DA(thrd->id));
> >> +
> >> +     spin_lock_irqsave(&pch->lock, flags);
> >> +
> >> +     /* Find the desc related to the current buffer. */
> >> +     list_for_each_entry(desc, &pch->work_list, node) {
> >> +             if (desc->rqcfg.src_inc && pl330_src_addr_in_desc(desc,
> >> sar)) {
> >> +                     residue = desc->px.bytes - (sar -
> > desc->px.src_addr);
> >> +                     goto found_unlock;
> >> +             }
> >> +             if (desc->rqcfg.dst_inc && pl330_dst_addr_in_desc(desc,
> >> dar)) {
> >> +                     residue = desc->px.bytes - (dar -
> > desc->px.dst_addr);
> >> +                     goto found_unlock;
> >> +             }
> >> +     }
> >> +
> >> +found_unlock:
> >> +     spin_unlock_irqrestore(&pch->lock, flags);
> >> +
> >> +     return residue;
> >> +}
> >> +
> >>  static enum dma_status
> >>  pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
> >>                struct dma_tx_state *txstate)  {
> >> -     return dma_cookie_status(chan, cookie, txstate);
> >> +     enum dma_status ret;
> >> +
> >> +     ret = dma_cookie_status(chan, cookie, txstate);
> >> +     if (ret != DMA_SUCCESS) /* Not complete, check amount left. */
> >> +             dma_set_residue(txstate, pl330_tx_residue(chan));
> >> +
> >> +     return ret;
> >
> > Why didn't you use a cookie value to track the request?
> > The cookie is assigned when each transfer is submitted.
> > If you save the value in the desc, we can find the request easily.
> 
> If there are several cyclic desc in the work list, is there a better way
> to find the "current" one?  The chan struct tracks the last completed and
> last submitted cookies, but these will be the first and last
> respectively as long as the cyclic transfer is active.  Is there an
> "active" cookie stored somewhere that I missed?

Assume there are three cookies. If you want to get the second cookie not
latest cookie, your way can be also correct in such case?
I think tx_status API is to get dma status of the given cookie.
You are only considering a cyclic case.

> 
> Looking for the first buffer with status == BUSY is an improvement I'll
> make.  Any way to avoid looking through the list?
> 
> Thanks,
> 
> Dylan
> 
> >
> > Thanks,
> >
> > Best  Regards,
> > Chanho Park
> >