@@ -66,11 +66,6 @@
* after the final transfer signalled by LBREQ or LSREQ. The DMAC
* will then move to the next LLI entry.
*
- * Only the former works sanely with scatter lists, so we only implement
- * the DMAC flow control method. However, peripherals which use the LBREQ
- * and LSREQ signals (eg, MMCI) are unable to use this mode, which through
- * these hardware restrictions prevents them from using scatter DMA.
- *
* Global TODO:
* - Break out common code from arch/arm/mach-s3c64xx and share
*/
@@ -615,6 +610,49 @@ static int pl08x_fill_llis_for_desc(struct pl08x_driver_data *pl08x,
sbus == &bd.srcbus ? "src" : "dst");
/*
+ * Zero length is only allowed if all these requirements are met:
+ * - flow controller is peripheral.
+ * - src.addr is aligned to src.width
+ * - dst.addr is aligned to dst.width
+ *
+ * sg_len == 1 should be true, as there can be two cases here:
+ * - Memory addresses are contiguous and are not scattered. Here, Only
+ * one sg will be passed by user driver, with memory address and zero
+ * length. We pass this to controller and after the transfer it will
+ * receive the last burst request from peripheral and so transfer
+ * finishes.
+ *
+ * - Memory addresses are scattered and are not contiguous. Here,
+ * Obviously as DMA controller doesn't know when a lli's transfer gets
+ * over, it can't load next lli. So in this case, there has to be an
+ * assumption that only one lli is supported. Thus, we can't have
+ * scattered addresses.
+ */
+ if (!bd.remainder) {
+ u32 fc = (txd->ccfg & PL080_CONFIG_FLOW_CONTROL_MASK) >>
+ PL080_CONFIG_FLOW_CONTROL_SHIFT;
+ if (!((fc >= PL080_FLOW_SRC2DST_DST) &&
+ (fc <= PL080_FLOW_SRC2DST_SRC))) {
+ dev_err(&pl08x->adev->dev, "%s sg len can't be zero",
+ __func__);
+ return 0;
+ }
+
+ if ((bd.srcbus.addr % bd.srcbus.buswidth) ||
+ (bd.srcbus.addr % bd.srcbus.buswidth)) {
+ dev_err(&pl08x->adev->dev,
+ "%s src & dst address must be aligned to src"
+ " & dst width if peripheral is flow controller",
+ __func__);
+ return 0;
+ }
+
+ cctl = pl08x_cctl_bits(cctl, bd.srcbus.buswidth,
+ bd.dstbus.buswidth, 0);
+ pl08x_fill_lli_for_desc(&bd, num_llis++, 0, cctl);
+ }
+
+ /*
* Send byte by byte for following cases
* - Less than a bus width available
* - until master bus is aligned
@@ -1255,7 +1293,7 @@ static struct dma_async_tx_descriptor *pl08x_prep_slave_sg(
struct pl08x_dma_chan *plchan = to_pl08x_chan(chan);
struct pl08x_driver_data *pl08x = plchan->host;
struct pl08x_txd *txd;
- int ret;
+ int ret, tmp;
/*
* Current implementation ASSUMES only one sg
@@ -1289,12 +1327,10 @@ static struct dma_async_tx_descriptor *pl08x_prep_slave_sg(
txd->len = sgl->length;
if (direction == DMA_TO_DEVICE) {
- txd->ccfg |= PL080_FLOW_MEM2PER << PL080_CONFIG_FLOW_CONTROL_SHIFT;
txd->cctl = plchan->dst_cctl;
txd->src_addr = sgl->dma_address;
txd->dst_addr = plchan->dst_addr;
} else if (direction == DMA_FROM_DEVICE) {
- txd->ccfg |= PL080_FLOW_PER2MEM << PL080_CONFIG_FLOW_CONTROL_SHIFT;
txd->cctl = plchan->src_cctl;
txd->src_addr = plchan->src_addr;
txd->dst_addr = sgl->dma_address;
@@ -1304,6 +1340,15 @@ static struct dma_async_tx_descriptor *pl08x_prep_slave_sg(
return NULL;
}
+ if (plchan->cd->device_fc)
+ tmp = (direction == DMA_TO_DEVICE) ? PL080_FLOW_MEM2PER_PER :
+ PL080_FLOW_PER2MEM_PER;
+ else
+ tmp = (direction == DMA_TO_DEVICE) ? PL080_FLOW_MEM2PER :
+ PL080_FLOW_PER2MEM;
+
+ txd->ccfg |= tmp << PL080_CONFIG_FLOW_CONTROL_SHIFT;
+
ret = pl08x_prep_channel_resources(plchan, txd);
if (ret)
return NULL;
@@ -47,6 +47,9 @@ enum {
* @muxval: a number usually used to poke into some mux regiser to
* mux in the signal to this channel
* @cctl_opt: default options for the channel control register
+ * @device_fc: Flow Controller Settings for ccfg register. Only valid for slave
+ * channels. Fill with 'true' if peripheral should be flow controller. Direction
+ * will be selected at Runtime.
* @addr: source/target address in physical memory for this DMA channel,
* can be the address of a FIFO register for burst requests for example.
* This can be left undefined if the PrimeCell API is used for configuring
@@ -65,6 +68,7 @@ struct pl08x_channel_data {
int max_signal;
u32 muxval;
u32 cctl;
+ bool device_fc;
dma_addr_t addr;
bool circular_buffer;
bool single;
At least, on SPEAr platforms there is one peripheral, JPEG, which can be flow controller for DMA transfer. Currently DMA controller driver didn't support peripheral flow controller configurations. This patch adds device_fc field in struct pl08x_channel_data, which will be used only for slave transfers and is not used in case of mem2mem transfers. Signed-off-by: Viresh Kumar <viresh.kumar@st.com> --- drivers/dma/amba-pl08x.c | 61 ++++++++++++++++++++++++++++++++++++++------ include/linux/amba/pl08x.h | 4 +++ 2 files changed, 57 insertions(+), 8 deletions(-)