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>
diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c
index e317deb..2ecefb7 100644
--- a/drivers/dma/ste_dma40.c
+++ b/drivers/dma/ste_dma40.c
@@ -355,6 +355,7 @@
* @allocated_dst: Same as for src but is dst.
* allocated_dst and allocated_src uses the D40_ALLOC* defines as well as
* event line number.
+ * @use_soft_lli: To mark if the linked lists of channel are managed by SW.
*/
struct d40_phy_res {
spinlock_t lock;
@@ -362,6 +363,7 @@
int num;
u32 allocated_src;
u32 allocated_dst;
+ bool use_soft_lli;
};
struct d40_base;
@@ -783,7 +785,16 @@
* can't link back to the one in LCPA space
*/
if (linkback || (lli_len - lli_current > 1)) {
- curr_lcla = d40_lcla_alloc_one(chan, desc);
+ /*
+ * If the channel is expected to use only soft_lli don't
+ * allocate a lcla. This is to avoid a HW issue that exists
+ * in some controller during a peripheral to memory transfer
+ * that uses linked lists.
+ */
+ if (!(chan->phy_chan->use_soft_lli &&
+ chan->dma_cfg.dir == STEDMA40_PERIPH_TO_MEM))
+ curr_lcla = d40_lcla_alloc_one(chan, desc);
+
first_lcla = curr_lcla;
}
@@ -3063,6 +3074,13 @@
num_phy_chans_avail--;
}
+ /* Mark soft_lli channels */
+ for (i = 0; i < base->plat_data->num_of_soft_lli_chans; i++) {
+ int chan = base->plat_data->soft_lli_chans[i];
+
+ base->phy_res[chan].use_soft_lli = true;
+ }
+
dev_info(base->dev, "%d of %d physical DMA channels available\n",
num_phy_chans_avail, base->num_phy_chans);