Re: [PATCH V2 2/4] dmaengine: xilinx_dma: Fix irq handler and start transfer path for AXI DMA

[Subbaraya Sundeep <sbhatta@marvell.com>]

On 2025-07-11 at 20:13:40, Gupta, Suraj (Suraj.Gupta2@amd.com) wrote:
> [Public]
> 
> > -----Original Message-----
> > From: Subbaraya Sundeep <sbhatta@marvell.com>
> > Sent: Friday, July 11, 2025 9:56 PM
> > To: Gupta, Suraj <Suraj.Gupta2@amd.com>
> > Cc: andrew+netdev@lunn.ch; davem@davemloft.net; kuba@kernel.org;
> > pabeni@redhat.com; Simek, Michal <michal.simek@amd.com>; vkoul@kernel.org;
> > Pandey, Radhey Shyam <radhey.shyam.pandey@amd.com>;
> > netdev@vger.kernel.org; linux-arm-kernel@lists.infradead.org; linux-
> > kernel@vger.kernel.org; dmaengine@vger.kernel.org; Katakam, Harini
> > <harini.katakam@amd.com>
> > Subject: Re: [PATCH V2 2/4] dmaengine: xilinx_dma: Fix irq handler and start transfer
> > path for AXI DMA
> >
> > Caution: This message originated from an External Source. Use proper caution when
> > opening attachments, clicking links, or responding.
> >
> >
> > On 2025-07-10 at 10:12:27, Suraj Gupta (suraj.gupta2@amd.com) wrote:
> > > AXI DMA driver incorrectly assumes complete transfer completion upon
> > > IRQ reception, particularly problematic when IRQ coalescing is active.
> > > Updating the tail pointer dynamically fixes it.
> > > Remove existing idle state validation in the beginning of
> > > xilinx_dma_start_transfer() as it blocks valid transfer initiation on
> > > busy channels with queued descriptors.
> > > Additionally, refactor xilinx_dma_start_transfer() to consolidate
> > > coalesce and delay configurations while conditionally starting
> > > channels only when idle.
> > >
> > > Signed-off-by: Suraj Gupta <suraj.gupta2@amd.com>
> > > Fixes: Fixes: c0bba3a99f07 ("dmaengine: vdma: Add Support for Xilinx
> > > AXI Direct Memory Access Engine")
> >
> > You series looks like net-next material and this one is fixing some existing bug. Send
> > this one patch seperately to net.
> > Also include net or net-next in subject.
> >
> > Thanks,
> > Sundeep
> 
> This series is more of DMAengine as we're enabling coalesce parameters configuration via DMAengine framework. AXI ethernet is just an example client using AXI DMA.
> 
> I sent V1 as separate patches for net-next and dmaengine mailing list and got suggestion[1] to send them as single series for better review, so I didn't used net specific subject prefix.
> [1]: https://lore.kernel.org/all/d5be7218-8ec1-4208-ac24-94d4831bfdb6@linux.dev/

My bad I forgot AXI ethernet and DMA are different IPs.

Thanks,
Sundeep
> 
> Regards,
> Suraj
> 
> > > ---
> > >  drivers/dma/xilinx/xilinx_dma.c | 20 ++++++++++----------
> > >  1 file changed, 10 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/drivers/dma/xilinx/xilinx_dma.c
> > > b/drivers/dma/xilinx/xilinx_dma.c index a34d8f0ceed8..187749b7b8a6
> > > 100644
> > > --- a/drivers/dma/xilinx/xilinx_dma.c
> > > +++ b/drivers/dma/xilinx/xilinx_dma.c
> > > @@ -1548,9 +1548,6 @@ static void xilinx_dma_start_transfer(struct
> > xilinx_dma_chan *chan)
> > >       if (list_empty(&chan->pending_list))
> > >               return;
> > >
> > > -     if (!chan->idle)
> > > -             return;
> > > -
> > >       head_desc = list_first_entry(&chan->pending_list,
> > >                                    struct xilinx_dma_tx_descriptor, node);
> > >       tail_desc = list_last_entry(&chan->pending_list,
> > > @@ -1558,23 +1555,24 @@ static void xilinx_dma_start_transfer(struct
> > xilinx_dma_chan *chan)
> > >       tail_segment = list_last_entry(&tail_desc->segments,
> > >                                      struct xilinx_axidma_tx_segment,
> > > node);
> > >
> > > +     if (chan->has_sg && list_empty(&chan->active_list))
> > > +             xilinx_write(chan, XILINX_DMA_REG_CURDESC,
> > > +                          head_desc->async_tx.phys);
> > > +
> > >       reg = dma_ctrl_read(chan, XILINX_DMA_REG_DMACR);
> > >
> > >       if (chan->desc_pendingcount <= XILINX_DMA_COALESCE_MAX) {
> > >               reg &= ~XILINX_DMA_CR_COALESCE_MAX;
> > >               reg |= chan->desc_pendingcount <<
> > >                                 XILINX_DMA_CR_COALESCE_SHIFT;
> > > -             dma_ctrl_write(chan, XILINX_DMA_REG_DMACR, reg);
> > >       }
> > >
> > > -     if (chan->has_sg)
> > > -             xilinx_write(chan, XILINX_DMA_REG_CURDESC,
> > > -                          head_desc->async_tx.phys);
> > >       reg  &= ~XILINX_DMA_CR_DELAY_MAX;
> > >       reg  |= chan->irq_delay << XILINX_DMA_CR_DELAY_SHIFT;
> > >       dma_ctrl_write(chan, XILINX_DMA_REG_DMACR, reg);
> > >
> > > -     xilinx_dma_start(chan);
> > > +     if (chan->idle)
> > > +             xilinx_dma_start(chan);
> > >
> > >       if (chan->err)
> > >               return;
> > > @@ -1914,8 +1912,10 @@ static irqreturn_t xilinx_dma_irq_handler(int irq, void
> > *data)
> > >                     XILINX_DMA_DMASR_DLY_CNT_IRQ)) {
> > >               spin_lock(&chan->lock);
> > >               xilinx_dma_complete_descriptor(chan);
> > > -             chan->idle = true;
> > > -             chan->start_transfer(chan);
> > > +             if (list_empty(&chan->active_list)) {
> > > +                     chan->idle = true;
> > > +                     chan->start_transfer(chan);
> > > +             }
> > >               spin_unlock(&chan->lock);
> > >       }
> > >
> > > --
> > > 2.25.1
> > >