linux-kernel - Re: [PATCH v4 13/15] dmaengine: dw-axi-dmac: Add Intel KeemBay AxiDMA handshake

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Date:   Wed, 18 Nov 2020 23:59:11 +0000
From:   Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
To:     Sia Jee Heng <jee.heng.sia@...el.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 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.

> +
> +       /*
> +        * 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
>