linux-kernel - Re: [PATCH v4 08/15] dmaengine: dw-axi-dmac: Support of_dma_controller

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Date:   Thu, 19 Nov 2020 00:10:05 +0000
From:   Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
To:     Sia Jee Heng <jee.heng.sia@...el.com>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
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 08/15] dmaengine: dw-axi-dmac: Support
 of_dma_controller_register()

Hi Sia,

> Subject: [PATCH v4 08/15] dmaengine: dw-axi-dmac: Support of_dma_controller_register()
> 
> Add support for of_dma_controller_register() so that DMA clients
> can pass in device handshake number to the AxiDMA driver.
> 
> DMA clients shall code the device handshake number in the Device tree.
> When DMA activities are needed, DMA clients shall invoke OF helper
> function to pass in the device handshake number to the AxiDMA.
> 
> Without register to the of_dma_controller_register(), data transfer
> between memory to device and device to memory operations would failed.
> 
> 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    | 26 +++++++++++++++++++
>  drivers/dma/dw-axi-dmac/dw-axi-dmac.h         |  1 +
>  2 files changed, 27 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 b5f92f9cb2bc..72871b8738be 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> @@ -20,6 +20,7 @@
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/of_dma.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/property.h>
> @@ -1044,6 +1045,22 @@ static int __maybe_unused axi_dma_runtime_resume(struct device *dev)
>         return axi_dma_resume(chip);
>  }
> 
> +static struct dma_chan *dw_axi_dma_of_xlate(struct of_phandle_args *dma_spec,
> +                                           struct of_dma *ofdma)
> +{
> +       struct dw_axi_dma *dw = ofdma->of_dma_data;
> +       struct axi_dma_chan *chan;
> +       struct dma_chan *dchan;
> +
> +       dchan = dma_get_any_slave_channel(&dw->dma);
> +       if (!dchan)
> +               return NULL;
> +
> +       chan = dchan_to_axi_dma_chan(dchan);
> +       chan->hw_hs_num = dma_spec->args[0];
> +       return dchan;
> +}
> +
>  static int parse_device_properties(struct axi_dma_chip *chip)
>  {
>         struct device *dev = chip->dev;
> @@ -1233,6 +1250,13 @@ static int dw_probe(struct platform_device *pdev)
>         if (ret)
>                 goto err_pm_disable;
> 
> +       /* Register with OF helpers for DMA lookups */
> +       ret = of_dma_controller_register(pdev->dev.of_node,
> +                                        dw_axi_dma_of_xlate, dw);
> +       if (ret < 0)
> +               dev_warn(&pdev->dev,
> +                        "Failed to register OF DMA controller, fallback to MEM_TO_MEM mode\n");
> +
>         dev_info(chip->dev, "DesignWare AXI DMA Controller, %d channels\n",
>                  dw->hdata->nr_channels);
> 
> @@ -1266,6 +1290,8 @@ static int dw_remove(struct platform_device *pdev)
> 
>         devm_free_irq(chip->dev, chip->irq, chip);
> 
> +       of_dma_controller_free(chip->dev->of_node);
> +
>         list_for_each_entry_safe(chan, _chan, &dw->dma.channels,
>                         vc.chan.device_node) {
>                 list_del(&chan->vc.chan.device_node);
> diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac.h b/drivers/dma/dw-axi-dmac/dw-axi-dmac.h
> index a26b0a242a93..651874e5c88f 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac.h
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac.h
> @@ -37,6 +37,7 @@ struct axi_dma_chan {
>         struct axi_dma_chip             *chip;
>         void __iomem                    *chan_regs;
>         u8                              id;
> +       u8                              hw_hs_num;
Just a nitpick: 'hw_hs_num' sounds quite obfuscated. Could it be 'hw_handshake_num' for example? 

>         atomic_t                        descs_allocated;
> 
>         struct dma_pool                 *desc_pool;
> --
> 2.18.0
>