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Date:   Fri, 20 Nov 2020 08:56:35 +0000
From:   "Sia, Jee Heng" <jee.heng.sia@...el.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
CC:     "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: [PATCH v4 13/15] dmaengine: dw-axi-dmac: Add Intel KeemBay AxiDMA
 handshake

Hi Eugeniy,

With regards to the below comment
> > In some places you check for this region existence using if
> > (IS_ERR(chip->regs)) and in other places you use if (!chip->apb_regs)
The main reason of using IS_ERR() is because of the ioremap() function return an error value
if the mapping failed.
And now with your suggestion to add conditional checking to the compatible property, the chip->apb will
remain NULL on non Intel KeemBay SoC. Therefore, the "if (!chip->apb_regs)" condition will be used instead.

Please let me  know if you have other concern.

> -----Original Message-----
> From: Sia, Jee Heng
> Sent: 20 November 2020 8:47 AM
> To: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> Cc: andriy.shevchenko@...ux.intel.com; dmaengine@...r.kernel.org; linux-
> kernel@...r.kernel.org; devicetree@...r.kernel.org
> Subject: RE: [PATCH v4 13/15] dmaengine: dw-axi-dmac: Add Intel KeemBay AxiDMA
> handshake
> 
> 
> 
> > -----Original Message-----
> > From: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> > Sent: 19 November 2020 7:59 AM
> > To: Sia, Jee Heng <jee.heng.sia@...el.com>
> > Cc: andriy.shevchenko@...ux.intel.com; dmaengine@...r.kernel.org;
> > linux- kernel@...r.kernel.org; devicetree@...r.kernel.org
> > Subject: Re: [PATCH v4 13/15] dmaengine: dw-axi-dmac: Add Intel
> > KeemBay AxiDMA handshake
> >
> > Hi Sia,
> >
> > > Subject: [PATCH v4 13/15] dmaengine: dw-axi-dmac: Add Intel KeemBay
> > > AxiDMA handshake
> > >
> > > Add support for Intel KeemBay AxiDMA device handshake programming.
> > > Device handshake number passed in to the AxiDMA shall be written to
> > > the Intel KeemBay AxiDMA hardware handshake registers before DMA
> > > operations are started.
> > >
> > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > > Signed-off-by: Sia Jee Heng <jee.heng.sia@...el.com>
> > > ---
> > >  .../dma/dw-axi-dmac/dw-axi-dmac-platform.c    | 52 +++++++++++++++++++
> > >  1 file changed, 52 insertions(+)
> > >
> > > diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> > > b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> > > index c2ffc5d44b6e..d44a5c9eb9c1 100644
> > > --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> > > +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> > > @@ -445,6 +445,48 @@ static void dma_chan_free_chan_resources(struct
> > dma_chan *dchan)
> > >         pm_runtime_put(chan->chip->dev);  }
> > >
> > > +static int dw_axi_dma_set_hw_channel(struct axi_dma_chip *chip, u32
> > hs_number,
> > > +                                    bool set) {
> > > +       unsigned long start = 0;
> > > +       unsigned long reg_value;
> > > +       unsigned long reg_mask;
> > > +       unsigned long reg_set;
> > > +       unsigned long mask;
> > > +       unsigned long val;
> > > +
> > > +       if (!chip->apb_regs)
> > > +               return -ENODEV;
> >
> > In some places you check for this region existence using if
> > (IS_ERR(chip->regs)) and in other places you use if (!chip->apb_regs)
> >
> > I guess it isn't correct. NOTE that this comment valid for other patches as well.
> [>>] Thanks for the invaluable comment, will make sure the consistency in the code.
> >
> > > +
> > > +       /*
> > > +        * An unused DMA channel has a default value of 0x3F.
> > > +        * Lock the DMA channel by assign a handshake number to the channel.
> > > +        * Unlock the DMA channel by assign 0x3F to the channel.
> > > +        */
> > > +       if (set) {
> > > +               reg_set = UNUSED_CHANNEL;
> > > +               val = hs_number;
> > > +       } else {
> > > +               reg_set = hs_number;
> > > +               val = UNUSED_CHANNEL;
> > > +       }
> > > +
> > > +       reg_value = lo_hi_readq(chip->apb_regs +
> > > + DMAC_APB_HW_HS_SEL_0);
> > > +
> > > +       for_each_set_clump8(start, reg_mask, &reg_value, 64) {
> > > +               if (reg_mask == reg_set) {
> > > +                       mask = GENMASK_ULL(start + 7, start);
> > > +                       reg_value &= ~mask;
> > > +                       reg_value |= rol64(val, start);
> > > +                       lo_hi_writeq(reg_value,
> > > +                                    chip->apb_regs + DMAC_APB_HW_HS_SEL_0);
> > > +                       break;
> > > +               }
> > > +       }
> > > +
> > > +       return 0;
> > > +}
> > > +
> > >  /*
> > >   * If DW_axi_dmac sees CHx_CTL.ShadowReg_Or_LLI_Last bit of the fetched LLI
> > >   * as 1, it understands that the current block is the final block
> > > in the @@ -626,6 +668,9 @@ dw_axi_dma_chan_prep_cyclic(struct
> > > dma_chan
> > *dchan, dma_addr_t dma_addr,
> > >                 llp = hw_desc->llp;
> > >         } while (num_periods);
> > >
> > > +       if (dw_axi_dma_set_hw_channel(chan->chip, chan->hw_hs_num, true))
> > > +               goto err_desc_get;
> > > +
> > >         return vchan_tx_prep(&chan->vc, &desc->vd, flags);
> > >
> > >  err_desc_get:
> > > @@ -684,6 +729,9 @@ dw_axi_dma_chan_prep_slave_sg(struct dma_chan
> > *dchan, struct scatterlist *sgl,
> > >                 llp = hw_desc->llp;
> > >         } while (sg_len);
> > >
> > > +       if (dw_axi_dma_set_hw_channel(chan->chip, chan->hw_hs_num, true))
> > > +               goto err_desc_get;
> > > +
> > >         return vchan_tx_prep(&chan->vc, &desc->vd, flags);
> > >
> > >  err_desc_get:
> > > @@ -959,6 +1007,10 @@ static int dma_chan_terminate_all(struct
> > > dma_chan
> > *dchan)
> > >                 dev_warn(dchan2dev(dchan),
> > >                          "%s failed to stop\n",
> > > axi_chan_name(chan));
> > >
> > > +       if (chan->direction != DMA_MEM_TO_MEM)
> > > +               dw_axi_dma_set_hw_channel(chan->chip,
> > > +                                         chan->hw_hs_num, false);
> > > +
> > >         spin_lock_irqsave(&chan->vc.lock, flags);
> > >
> > >         vchan_get_all_descriptors(&chan->vc, &head);
> > > --
> > > 2.18.0
> > >

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