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From:   PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Date:   Wed, 4 Jul 2018 21:58:15 +0530
Message-ID: <CANc+2y4ZJDKou4x570zNv82fSAxiOpbZfd3rFNB2M5Ft1C3eiQ@mail.gmail.com>
Subject: Re: [PATCH 01/14] dmaengine: dma-jz4780: Avoid hardcoding number of channels
To:     Paul Cercueil <paul@crapouillou.net>
Cc:     Vinod Koul <vkoul@kernel.org>, Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Ralf Baechle <ralf@linux-mips.org>,
        Paul Burton <paul.burton@mips.com>,
        James Hogan <jhogan@kernel.org>,
        Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>,
        Mathieu Malaterre <malat@debian.org>,
        Daniel Silsby <dansilsby@gmail.com>, dmaengine@vger.kernel.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        Linux-MIPS <linux-mips@linux-mips.org>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi Paul,

On 3 July 2018 at 18:02, Paul Cercueil <paul@crapouillou.net> wrote:
> As part of the work to support various other Ingenic JZ47xx SoC versions,
> which don't feature the same number of DMA channels per core, we now
> deduce the number of DMA channels available from the devicetree
> compatible string.
>
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> ---
>  drivers/dma/dma-jz4780.c | 53 +++++++++++++++++++++++++++++-----------
>  1 file changed, 39 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
> index 85820a2d69d4..b40f491f0367 100644
> --- a/drivers/dma/dma-jz4780.c
> +++ b/drivers/dma/dma-jz4780.c
> @@ -16,6 +16,7 @@
>  #include <linux/interrupt.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/of_device.h>
>  #include <linux/of_dma.h>
>  #include <linux/platform_device.h>
>  #include <linux/slab.h>
> @@ -23,8 +24,6 @@
>  #include "dmaengine.h"
>  #include "virt-dma.h"
>
> -#define JZ_DMA_NR_CHANNELS     32
> -
>  /* Global registers. */
>  #define JZ_DMA_REG_DMAC                0x1000
>  #define JZ_DMA_REG_DIRQP       0x1004
> @@ -135,14 +134,20 @@ struct jz4780_dma_chan {
>         unsigned int curr_hwdesc;
>  };
>
> +enum jz_version {
> +       ID_JZ4780,
> +};
> +
>  struct jz4780_dma_dev {
>         struct dma_device dma_device;
>         void __iomem *base;
>         struct clk *clk;
>         unsigned int irq;
> +       unsigned int nb_channels;
> +       enum jz_version version;
>
>         uint32_t chan_reserved;
> -       struct jz4780_dma_chan chan[JZ_DMA_NR_CHANNELS];
> +       struct jz4780_dma_chan chan[];

Looks like a variable length array in struct. I think there is some
effort to remove the usage of VLA. Can you revisit this? I may be
wrong, please feel free to correct.

>  };
>
>  struct jz4780_dma_filter_data {
> @@ -648,7 +653,7 @@ static irqreturn_t jz4780_dma_irq_handler(int irq, void *data)
>
>         pending = jz4780_dma_readl(jzdma, JZ_DMA_REG_DIRQP);
>
> -       for (i = 0; i < JZ_DMA_NR_CHANNELS; i++) {
> +       for (i = 0; i < jzdma->nb_channels; i++) {
>                 if (!(pending & (1<<i)))
>                         continue;
>
> @@ -728,7 +733,7 @@ static struct dma_chan *jz4780_of_dma_xlate(struct of_phandle_args *dma_spec,
>         data.channel = dma_spec->args[1];
>
>         if (data.channel > -1) {
> -               if (data.channel >= JZ_DMA_NR_CHANNELS) {
> +               if (data.channel >= jzdma->nb_channels) {
>                         dev_err(jzdma->dma_device.dev,
>                                 "device requested non-existent channel %u\n",
>                                 data.channel);
> @@ -752,19 +757,45 @@ static struct dma_chan *jz4780_of_dma_xlate(struct of_phandle_args *dma_spec,
>         }
>  }
>
> +static const unsigned int jz4780_dma_nb_channels[] = {
> +       [ID_JZ4780] = 32,
> +};
> +
> +static const struct of_device_id jz4780_dma_dt_match[] = {
> +       { .compatible = "ingenic,jz4780-dma", .data = (void *)ID_JZ4780 },
> +       {},
> +};
> +MODULE_DEVICE_TABLE(of, jz4780_dma_dt_match);
> +
>  static int jz4780_dma_probe(struct platform_device *pdev)
>  {
>         struct device *dev = &pdev->dev;
> +       const struct of_device_id *of_id = of_match_device(
> +                       jz4780_dma_dt_match, dev);
>         struct jz4780_dma_dev *jzdma;
>         struct jz4780_dma_chan *jzchan;
>         struct dma_device *dd;
>         struct resource *res;
> +       enum jz_version version;
> +       unsigned int nb_channels;
>         int i, ret;
>
> -       jzdma = devm_kzalloc(dev, sizeof(*jzdma), GFP_KERNEL);
> +       if (of_id)
> +               version = (enum jz_version)of_id->data;
> +       else
> +               version = ID_JZ4780; /* Default when not probed from DT */
> +
> +       nb_channels = jz4780_dma_nb_channels[version];
> +
> +       jzdma = devm_kzalloc(dev, sizeof(*jzdma)
> +                               + sizeof(*jzdma->chan) * nb_channels,
> +                               GFP_KERNEL);
>         if (!jzdma)
>                 return -ENOMEM;
>
> +       jzdma->nb_channels = nb_channels;
> +       jzdma->version = version;
> +
>         platform_set_drvdata(pdev, jzdma);
>
>         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> @@ -839,7 +870,7 @@ static int jz4780_dma_probe(struct platform_device *pdev)
>
>         INIT_LIST_HEAD(&dd->channels);
>
> -       for (i = 0; i < JZ_DMA_NR_CHANNELS; i++) {
> +       for (i = 0; i < jzdma->nb_channels; i++) {
>                 jzchan = &jzdma->chan[i];
>                 jzchan->id = i;
>
> @@ -884,19 +915,13 @@ static int jz4780_dma_remove(struct platform_device *pdev)
>
>         free_irq(jzdma->irq, jzdma);
>
> -       for (i = 0; i < JZ_DMA_NR_CHANNELS; i++)
> +       for (i = 0; i < jzdma->nb_channels; i++)
>                 tasklet_kill(&jzdma->chan[i].vchan.task);
>
>         dma_async_device_unregister(&jzdma->dma_device);
>         return 0;
>  }
>
> -static const struct of_device_id jz4780_dma_dt_match[] = {
> -       { .compatible = "ingenic,jz4780-dma", .data = NULL },
> -       {},
> -};
> -MODULE_DEVICE_TABLE(of, jz4780_dma_dt_match);
> -
>  static struct platform_driver jz4780_dma_driver = {
>         .probe          = jz4780_dma_probe,
>         .remove         = jz4780_dma_remove,
> --
> 2.18.0
>
>