Re: [PATCH 01/14] dmaengine: dma-jz4780: Avoid hardcoding number of channels

[Paul Cercueil]

Hi PrasannaKumar,

> Hi Paul,
>
> On 3 July 2018 at 18:02, Paul Cercueil <paul@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
> >  ---
> >   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.

Are you sure? It's the first time I hear about it.
Could anybody confirm?

> >   };
> >
> >   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