dmaengine: ste_dma40: add software lli support

This patch add support to manage LLI by SW for select phy channels.

There is a HW issue in certain controllers due to which on certain
occassions HW LLI cannot be used on some physical channels.  To avoid
the HW issue on a specific phy channel, the phy channel number can be
added to the list of soft_lli_channels and there after all the transfers
on that channel will use software LLI, for peripheral to memory
transfers.

SoftLLI introduces relink overhead, that could impact performace for
certain use cases.

This is based on a previous patch of Narayanan Gopalakrishnan.

Cc: Shreshtha Kumar Sahu <shreshthakumar.sahu@stericsson.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/platform_data/dma-ste-dma40.h b/include/linux/platform_data/dma-ste-dma40.h
index b99024ba94ec..4b781014b0a0 100644
--- a/include/linux/platform_data/dma-ste-dma40.h
+++ b/include/linux/platform_data/dma-ste-dma40.h
@@ -147,6 +147,12 @@ struct stedma40_chan_cfg {
  * @memcpy_conf_log: default configuration of logical channel memcpy
  * @disabled_channels: A vector, ending with -1, that marks physical channels
  * that are for different reasons not available for the driver.
+ * @soft_lli_chans: A vector, that marks physical channels will use LLI by SW
+ * which avoids HW bug that exists in some versions of the controller.
+ * SoftLLI introduces relink overhead that could impact performace for
+ * certain use cases.
+ * @num_of_soft_lli_chans: The number of channels that needs to be configured
+ * to use SoftLLI.
  * @use_esram_lcla: flag for mapping the lcla into esram region
  * @num_of_phy_chans: The number of physical channels implemented in HW.
  * 0 means reading the number of channels from DMA HW but this is only valid
@@ -161,6 +167,8 @@ struct stedma40_platform_data {
 	struct stedma40_chan_cfg	*memcpy_conf_phy;
 	struct stedma40_chan_cfg	*memcpy_conf_log;
 	int				 disabled_channels[STEDMA40_MAX_PHYS];
+	int				*soft_lli_chans;
+	int				 num_of_soft_lli_chans;
 	bool				 use_esram_lcla;
 	int				 num_of_phy_chans;
 };