Re: [RFC v02 03/15] dmaengine: core: Introduce new, universal API to request a channel

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On Mon, Nov 30, 2015 at 3:45 PM, Peter Ujfalusi <peter.ujfalusi@xxxxxx> wrote:
> The two API function can cover most, if not all current APIs used to
> request a channel. With minimal effort dmaengine drivers, platforms and
> dmaengine user drivers can be converted to use the two function.
>
> struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask);
>
> To request any channel matching with the requested capabilities, can be
> used to request channel for memcpy, memset, xor, etc where no hardware
> synchronization is needed.
>
> struct dma_chan *dma_request_chan(struct device *dev, const char *name);
> To request a slave channel. The dma_request_chan() will try to find the
> channel via DT, ACPI or in case if the kernel booted in non DT/ACPI mode
> it will use a filter lookup table and retrieves the needed information from
> the dma_filter_map provided by the DMA drivers.
> This legacy mode needs changes in platform code, in dmaengine drivers and
> finally the dmaengine user drivers can be converted:
>
> For each dmaengine driver an array of DMA device, slave and the parameter
> for the filter function needs to be added:
>
> static struct dma_filter_map da830_edma_map[] = {
>         DMA_FILTER_ENTRY("davinci-mcasp.0", "rx", EDMA_CTLR_CHAN(0, 0)),
>         DMA_FILTER_ENTRY("davinci-mcasp.0", "tx", EDMA_CTLR_CHAN(0, 1)),
>         DMA_FILTER_ENTRY("davinci-mcasp.1", "rx", EDMA_CTLR_CHAN(0, 2)),
>         DMA_FILTER_ENTRY("davinci-mcasp.1", "tx", EDMA_CTLR_CHAN(0, 3)),
>         DMA_FILTER_ENTRY("davinci-mcasp.2", "rx", EDMA_CTLR_CHAN(0, 4)),
>         DMA_FILTER_ENTRY("davinci-mcasp.2", "tx", EDMA_CTLR_CHAN(0, 5)),
>         DMA_FILTER_ENTRY("spi_davinci.0", "rx", EDMA_CTLR_CHAN(0, 14)),
>         DMA_FILTER_ENTRY("spi_davinci.0", "tx", EDMA_CTLR_CHAN(0, 15)),
>         DMA_FILTER_ENTRY("da830-mmc.0", "rx", EDMA_CTLR_CHAN(0, 16)),
>         DMA_FILTER_ENTRY("da830-mmc.0", "tx", EDMA_CTLR_CHAN(0, 17)),
>         DMA_FILTER_ENTRY("spi_davinci.1", "rx", EDMA_CTLR_CHAN(0, 18)),
>         DMA_FILTER_ENTRY("spi_davinci.1", "tx", EDMA_CTLR_CHAN(0, 19)),
> };
>
> This information is going to be needed by the dmaengine driver, so
> modification to the platform_data is needed, and the driver map should be
> added to the pdata of the DMA driver:
>
> da8xx_edma0_pdata.filter_map = da830_edma_map;
> da8xx_edma0_pdata.filtercnt = ARRAY_SIZE(da830_edma_map);
>
> The DMA driver then needs to convigure the needed device -> filter_fn
> mapping before it registers with dma_async_device_register() :
>
> if (info->filter_map) {
>         ecc->dma_slave.filter_map.map = info->filter_map;
>         ecc->dma_slave.filter_map.mapcnt = info->filtercnt;
>         ecc->dma_slave.filter_map.filter_fn = edma_filter_for_map;
> }
>
> When neither DT or ACPI lookup is available the dma_request_chan() will
> try to match the requester's device name with the filter_map's list of
> device names, when a match found it will use the information from the
> dma_filter_map to get the channel with the dma_get_channel() internal
> function.
>
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
> ---
>  drivers/dma/dmaengine.c   | 76 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/dmaengine.h | 31 +++++++++++++++++++
>  2 files changed, 107 insertions(+)
>
> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> index 1249165fb4b2..bd774adff697 100644
> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -43,6 +43,7 @@
>
>  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> +#include <linux/platform_device.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/init.h>
>  #include <linux/module.h>
> @@ -715,6 +716,81 @@ struct dma_chan *dma_request_slave_channel(struct device *dev,
>  }
>  EXPORT_SYMBOL_GPL(dma_request_slave_channel);
>
> +static struct dma_filter_map *dma_filter_match(struct dma_device *device,
> +                                              const char *name,
> +                                              struct device *dev)
> +{
> +       struct dma_filter_map *map_found = NULL;
> +       int i;
> +
> +       if (!device->filter_map.mapcnt)
> +               return NULL;
> +
> +       for (i = 0; i < device->filter_map.mapcnt; i++) {
> +               struct dma_filter_map *map = &device->filter_map.map[i];
> +
> +               if (!strcmp(map->devname, dev_name(dev)) &&
> +                   !strcmp(map->slave, name)) {
> +                       map_found = map;
> +                       break;
> +               }
> +       }
> +
> +       return map_found;
> +}
> +
> +struct dma_chan *dma_request_chan(struct device *dev, const char *name)
> +{
> +       struct dma_device *device, *_d;
> +       struct dma_chan *chan = NULL;
> +
> +       /* If device-tree is present get slave info from here */
> +       if (dev->of_node)
> +               chan = of_dma_request_slave_channel(dev->of_node, name);
> +
> +       /* If device was enumerated by ACPI get slave info from here */
> +       if (ACPI_HANDLE(dev) && !chan)

The preferable way is to use
has_acpi_companion() instead of ACPI_HANDLE().

> +               chan = acpi_dma_request_slave_chan_by_name(dev, name);
> +
> +       if (chan)
> +               return chan;
> +
> +       /* Try to find the channel via the DMA filter map(s) */
> +       mutex_lock(&dma_list_mutex);
> +       list_for_each_entry_safe(device, _d, &dma_device_list, global_node) {
> +               struct dma_filter_map *map = dma_filter_match(device, name,
> +                                                             dev);
> +
> +               if (!map)
> +                       continue;
> +
> +               chan = dma_get_channel(device, NULL,
> +                                      device->filter_map.filter_fn,
> +                                      map->param);
> +               if (!IS_ERR(chan))
> +                       break;
> +       }
> +       mutex_unlock(&dma_list_mutex);
> +
> +       return chan ? chan : ERR_PTR(-EPROBE_DEFER);
> +}
> +EXPORT_SYMBOL_GPL(dma_request_chan);
> +
> +struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask)
> +{
> +       struct dma_chan *chan;
> +
> +       if (!mask)
> +               return ERR_PTR(-ENODEV);
> +
> +       chan = __dma_request_channel(mask, NULL, NULL);
> +       if (!chan)
> +               chan = ERR_PTR(-ENODEV);
> +
> +       return chan;
> +}
> +EXPORT_SYMBOL_GPL(dma_request_chan_by_mask);
> +
>  void dma_release_channel(struct dma_chan *chan)
>  {
>         mutex_lock(&dma_list_mutex);
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index a2b7c2071cf4..f7b06ff982c8 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -606,6 +606,24 @@ enum dmaengine_alignment {
>         DMAENGINE_ALIGN_64_BYTES = 6,
>  };
>
> +struct dma_filter_map {
> +        char *devname;
> +        char *slave;
> +        void *param;
> +};
> +#define DMA_FILTER_ENTRY(_devname, _slave, _param)     \
> +       {                                               \
> +               .devname = _devname,                    \
> +               .slave = _slave,                        \
> +               .param = (void*)_param,                 \
> +       }
> +
> +struct dma_filter {
> +        dma_filter_fn filter_fn;
> +        int mapcnt;
> +        struct dma_filter_map *map;
> +};
> +
>  /**
>   * struct dma_device - info on the entity supplying DMA services
>   * @chancnt: how many DMA channels are supported
> @@ -669,6 +687,7 @@ struct dma_device {
>         unsigned int privatecnt;
>         struct list_head channels;
>         struct list_head global_node;
> +       struct dma_filter filter_map;
>         dma_cap_mask_t  cap_mask;
>         unsigned short max_xor;
>         unsigned short max_pq;
> @@ -1235,6 +1254,10 @@ struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
>  struct dma_chan *dma_request_slave_channel_reason(struct device *dev,
>                                                   const char *name);
>  struct dma_chan *dma_request_slave_channel(struct device *dev, const char *name);
> +
> +struct dma_chan *dma_request_chan(struct device *dev, const char *name);
> +struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask);
> +
>  void dma_release_channel(struct dma_chan *chan);
>  int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps);
>  #else
> @@ -1268,6 +1291,14 @@ static inline struct dma_chan *dma_request_slave_channel(struct device *dev,
>  {
>         return NULL;
>  }
> +static inline struct dma_chan *dma_request_chan(struct device *dev)
> +{
> +       return ERR_PTR(-ENODEV);
> +}
> +static inline struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask)
> +{
> +       return ERR_PTR(-ENODEV);
> +}
>  static inline void dma_release_channel(struct dma_chan *chan)
>  {
>  }
> --
> 2.6.3
>



-- 
With Best Regards,
Andy Shevchenko
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