ARM: mmci: add dmaengine-based DMA support

Based on a patch from Linus Walleij.

Add dmaengine based support for DMA to the MMCI driver, using the
Primecell DMA engine interface.  The changes over Linus' driver are:

- rename txsize_threshold to dmasize_threshold, as this reflects the
  purpose more.
- use 'mmci_dma_' as the function prefix rather than 'dma_mmci_'.
- clean up requesting of dma channels.
- don't release a single channel twice when it's shared between tx and rx.
- get rid of 'dma_enable' bool - instead check whether the channel is NULL.
- detect incomplete DMA at the end of a transfer.  Some DMA controllers
  (eg, PL08x) are unable to be configured for scatter DMA and also listen
  to all four DMA request signals [BREQ,SREQ,LBREQ,LSREQ] from the MMCI.
  They can do one or other but not both.  As MMCI uses LBREQ/LSREQ for the
  final burst/words, PL08x does not transfer the last few words.
- map and unmap DMA buffers using the DMA engine struct device, not the
  MMCI struct device - the DMA engine is doing the DMA transfer, not us.
- avoid double-unmapping of the DMA buffers on MMCI data errors.
- don't check for negative values from the dmaengine tx submission
  function - Dan says this must never fail.
- use new dmaengine helper functions rather than using the ugly function
  pointers directly.
- allow DMA code to be fully optimized away using dma_inprogress() which
  is defined to constant 0 if DMA engine support is disabled.
- request maximum segment size from the DMA engine struct device and
  set this appropriately.
- removed checking of buffer alignment - the DMA engine should deal with
  its own restrictions on buffer alignment, not the individual DMA engine
  users.
- removed setting DMAREQCTL - this confuses some DMA controllers as it
  causes LBREQ to be asserted for the last seven transfers, rather than
  six SREQ and one LSREQ.
- removed burst setting - the DMA controller should not burst past the
  transfer size required to complete the DMA operation.

Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 17 insertions, 0 deletions

diff --git a/include/linux/amba/mmci.h b/include/linux/amba/mmci.h
index f4ee9acc9721..f60227088b7b 100644
--- a/include/linux/amba/mmci.h
+++ b/include/linux/amba/mmci.h
@@ -6,6 +6,9 @@
 
 #include <linux/mmc/host.h>
 
+/* Just some dummy forwarding */
+struct dma_chan;
+
 /**
  * struct mmci_platform_data - platform configuration for the MMCI
  * (also known as PL180) block.
@@ -27,6 +30,17 @@
  * @cd_invert: true if the gpio_cd pin value is active low
  * @capabilities: the capabilities of the block as implemented in
  * this platform, signify anything MMC_CAP_* from mmc/host.h
+ * @dma_filter: function used to select an apropriate RX and TX
+ * DMA channel to be used for DMA, if and only if you're deploying the
+ * generic DMA engine
+ * @dma_rx_param: parameter passed to the DMA allocation
+ * filter in order to select an apropriate RX channel. If
+ * there is a bidirectional RX+TX channel, then just specify
+ * this and leave dma_tx_param set to NULL
+ * @dma_tx_param: parameter passed to the DMA allocation
+ * filter in order to select an apropriate TX channel. If this
+ * is NULL the driver will attempt to use the RX channel as a
+ * bidirectional channel
  */
 struct mmci_platform_data {
         unsigned int f_max;
@@ -38,6 +52,9 @@ struct mmci_platform_data {
         int     gpio_cd;
         bool    cd_invert;
         unsigned long capabilities;
+        bool (*dma_filter)(struct dma_chan *chan, void *filter_param);
+        void *dma_rx_param;
+        void *dma_tx_param;
 };
 
 #endif