dmaengine: Introduce DMA-device device_caps callback

There are DMA devices (like ours version of Synopsys DW DMAC) which have
DMA capabilities non-uniformly redistributed between the device channels.
In order to provide a way of exposing the channel-specific parameters to
the DMA engine consumers, we introduce a new DMA-device callback. In case
if provided it gets called from the dma_get_slave_caps() method and is
able to override the generic DMA-device capabilities.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200723005848.31907-6-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 8177f78..a53e71d 100644 (file)
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -601,6 +601,16 @@ int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps)
        caps->cmd_resume = !!device->device_resume;
        caps->cmd_terminate = !!device->device_terminate_all;
 
+       /*
+        * DMA engine device might be configured with non-uniformly
+        * distributed slave capabilities per device channels. In this
+        * case the corresponding driver may provide the device_caps
+        * callback to override the generic capabilities with
+        * channel-specific ones.
+        */
+       if (device->device_caps)
+               device->device_caps(chan, caps);
+
        return 0;
 }
 EXPORT_SYMBOL_GPL(dma_get_slave_caps);

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 4cbe09e..d718671 100644 (file)
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -801,6 +801,8 @@ struct dma_filter {
  *     be called after period_len bytes have been transferred.
  * @device_prep_interleaved_dma: Transfer expression in a generic way.
  * @device_prep_dma_imm_data: DMA's 8 byte immediate data to the dst address
+ * @device_caps: May be used to override the generic DMA slave capabilities
+ *     with per-channel specific ones
  * @device_config: Pushes a new configuration to a channel, return 0 or an error
  *     code
  * @device_pause: Pauses any transfer happening on a channel. Returns
@@ -901,6 +903,8 @@ struct dma_device {
                struct dma_chan *chan, dma_addr_t dst, u64 data,
                unsigned long flags);
 
+       void (*device_caps)(struct dma_chan *chan,
+                           struct dma_slave_caps *caps);
        int (*device_config)(struct dma_chan *chan,
                             struct dma_slave_config *config);
        int (*device_pause)(struct dma_chan *chan);