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Subject[PATCH 2/2] dw_dmac: add cyclic API to DW DMA driver
Date
This patch adds a cyclic DMA interface to the DW DMA driver. This is
very useful if you want to use the DMA controller in combination with a
sound device which uses cyclic buffers.

Using a DMA channel for cyclic DMA will disable the possibility to use
it as a normal DMA engine until the user calls the cyclic free function
on the DMA channel. Also a cyclic DMA list can not be prepared if the
channel is already active.

Signed-off-by: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
---
drivers/dma/dw_dmac.c | 303 +++++++++++++++++++++++++++++++++++++++++++-
drivers/dma/dw_dmac_regs.h | 7 +-
include/linux/dw_dmac.h | 19 +++
3 files changed, 327 insertions(+), 2 deletions(-)
diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
index 1c5e31d..9e7160d 100644
--- a/drivers/dma/dw_dmac.c
+++ b/drivers/dma/dw_dmac.c
@@ -363,6 +363,84 @@ static void dwc_handle_error(struct dw_dma *dw, struct dw_dma_chan *dwc)
dwc_descriptor_complete(dwc, bad_desc);
}

+/* --------------------- Cyclic DMA API extensions -------------------- */
+
+inline dma_addr_t dw_dma_get_src_addr(struct dma_chan *chan)
+{
+ struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
+ return channel_readl(dwc, SAR);
+}
+EXPORT_SYMBOL(dw_dma_get_src_addr);
+
+inline dma_addr_t dw_dma_get_dst_addr(struct dma_chan *chan)
+{
+ struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
+ return channel_readl(dwc, DAR);
+}
+EXPORT_SYMBOL(dw_dma_get_dst_addr);
+
+/* called with dwc->lock held and all interrupts disabled */
+static void dwc_handle_cyclic(struct dw_dma *dw, struct dw_dma_chan *dwc,
+ u32 status_block, u32 status_err, u32 status_xfer)
+{
+ if (status_block & dwc->mask) {
+ void (*callback)(void *param);
+ void *callback_param;
+
+ dev_vdbg(chan2dev(&dwc->chan), "new cyclic period llp 0x%08x\n",
+ channel_readl(dwc, LLP));
+ dma_writel(dw, CLEAR.BLOCK, dwc->mask);
+
+ callback = dwc->cdesc->period_callback;
+ callback_param = dwc->cdesc->period_callback_param;
+ if (callback) {
+ spin_unlock(&dwc->lock);
+ callback(callback_param);
+ spin_lock(&dwc->lock);
+ }
+ }
+
+ /*
+ * Error and transfer complete are highly unlikely, and will most
+ * likely be due to a configuration error by the user.
+ */
+ if (unlikely(status_err & dwc->mask) ||
+ unlikely(status_xfer & dwc->mask)) {
+ int i;
+
+ dev_err(chan2dev(&dwc->chan), "cyclic DMA unexpected %s "
+ "interrupt, stopping DMA transfer\n",
+ status_xfer ? "xfer" : "error");
+ dev_err(chan2dev(&dwc->chan),
+ " SAR: 0x%x DAR: 0x%x LLP: 0x%x CTL: 0x%x:%08x\n",
+ channel_readl(dwc, SAR),
+ channel_readl(dwc, DAR),
+ channel_readl(dwc, LLP),
+ channel_readl(dwc, CTL_HI),
+ channel_readl(dwc, CTL_LO));
+
+ channel_clear_bit(dw, CH_EN, dwc->mask);
+ while (dma_readl(dw, CH_EN) & dwc->mask)
+ cpu_relax();
+
+ /* make sure DMA does not restart by loading a new list */
+ channel_writel(dwc, LLP, 0);
+ channel_writel(dwc, CTL_LO, 0);
+ channel_writel(dwc, CTL_HI, 0);
+
+ dma_writel(dw, CLEAR.BLOCK, dwc->mask);
+ dma_writel(dw, CLEAR.ERROR, dwc->mask);
+ dma_writel(dw, CLEAR.XFER, dwc->mask);
+
+ for (i = 0; i < dwc->cdesc->periods; i++)
+ dwc_dump_lli(dwc, &dwc->cdesc->desc[i]->lli);
+
+ return;
+ }
+}
+
+/* ------------------------------------------------------------------------- */
+
static void dw_dma_tasklet(unsigned long data)
{
struct dw_dma *dw = (struct dw_dma *)data;
@@ -382,7 +460,10 @@ static void dw_dma_tasklet(unsigned long data)
for (i = 0; i < dw->dma.chancnt; i++) {
dwc = &dw->chan[i];
spin_lock(&dwc->lock);
- if (status_err & (1 << i))
+ if (test_bit(DW_DMA_IS_CYCLIC, &dwc->flags))
+ dwc_handle_cyclic(dw, dwc, status_block, status_err,
+ status_xfer);
+ else if (status_err & (1 << i))
dwc_handle_error(dw, dwc);
else if ((status_block | status_xfer) & (1 << i))
dwc_scan_descriptors(dw, dwc);
@@ -884,6 +965,226 @@ static void dwc_free_chan_resources(struct dma_chan *chan)
dev_vdbg(chan2dev(chan), "free_chan_resources done\n");
}

+/* --------------------- Cyclic DMA API extensions -------------------- */
+
+int dw_dma_cyclic_start(struct dma_chan *chan)
+{
+ struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
+ struct dw_dma *dw = to_dw_dma(dwc->chan.device);
+
+ if (!test_bit(DW_DMA_IS_CYCLIC, &dwc->flags)) {
+ dev_err(chan2dev(&dwc->chan), "missing prep for cyclic DMA\n");
+ return -ENODEV;
+ }
+
+ spin_lock(&dwc->lock);
+
+ /* assert channel is idle */
+ if (dma_readl(dw, CH_EN) & dwc->mask) {
+ dev_err(chan2dev(&dwc->chan),
+ "BUG: Attempted to start non-idle channel\n");
+ dev_err(chan2dev(&dwc->chan),
+ " SAR: 0x%x DAR: 0x%x LLP: 0x%x CTL: 0x%x:%08x\n",
+ channel_readl(dwc, SAR),
+ channel_readl(dwc, DAR),
+ channel_readl(dwc, LLP),
+ channel_readl(dwc, CTL_HI),
+ channel_readl(dwc, CTL_LO));
+ spin_unlock(&dwc->lock);
+ return -EBUSY;
+ }
+
+ dma_writel(dw, CLEAR.BLOCK, dwc->mask);
+ dma_writel(dw, CLEAR.ERROR, dwc->mask);
+ dma_writel(dw, CLEAR.XFER, dwc->mask);
+
+ /* setup DMAC channel registers */
+ channel_writel(dwc, LLP, dwc->cdesc->desc[0]->txd.phys);
+ channel_writel(dwc, CTL_LO, DWC_CTLL_LLP_D_EN | DWC_CTLL_LLP_S_EN);
+ channel_writel(dwc, CTL_HI, 0);
+
+ channel_set_bit(dw, CH_EN, dwc->mask);
+
+ spin_unlock(&dwc->lock);
+
+ return 0;
+}
+EXPORT_SYMBOL(dw_dma_cyclic_start);
+
+void dw_dma_cyclic_stop(struct dma_chan *chan)
+{
+ struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
+ struct dw_dma *dw = to_dw_dma(dwc->chan.device);
+
+ channel_clear_bit(dw, CH_EN, dwc->mask);
+ while (dma_readl(dw, CH_EN) & dwc->mask)
+ cpu_relax();
+}
+EXPORT_SYMBOL(dw_dma_cyclic_stop);
+
+struct dw_cyclic_desc *dw_dma_cyclic_prep(struct dma_chan *chan,
+ dma_addr_t buf_addr, size_t buf_len, size_t period_len,
+ enum dma_data_direction direction)
+{
+ struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
+ struct dw_cyclic_desc *cdesc;
+ struct dw_cyclic_desc *retval = NULL;
+ struct dw_desc *desc;
+ struct dw_desc *last = NULL;
+ struct dw_dma_slave *dws = chan->private;
+ unsigned long was_cyclic;
+ unsigned int reg_width;
+ unsigned int periods;
+ unsigned int i;
+
+ spin_lock_bh(&dwc->lock);
+ if (!list_empty(&dwc->queue) || !list_empty(&dwc->active_list)) {
+ spin_unlock_bh(&dwc->lock);
+ dev_dbg(chan2dev(&dwc->chan),
+ "queue and/or active list are not empty\n");
+ return ERR_PTR(-EBUSY);
+ }
+
+ was_cyclic = test_and_set_bit(DW_DMA_IS_CYCLIC, &dwc->flags);
+ if (was_cyclic) {
+ spin_unlock_bh(&dwc->lock);
+ dev_dbg(chan2dev(&dwc->chan),
+ "channel already prepared for cyclic DMA\n");
+ return ERR_PTR(-EBUSY);
+ }
+ spin_unlock_bh(&dwc->lock);
+
+ retval = ERR_PTR(-EINVAL);
+ reg_width = dws->reg_width;
+ periods = buf_len / period_len;
+
+ /* Check for too big/unaligned periods and unaligned DMA buffer. */
+ if (period_len > (DWC_MAX_COUNT << reg_width))
+ goto out_err;
+ if (unlikely(period_len & ((1 << reg_width) - 1)))
+ goto out_err;
+ if (unlikely(buf_addr & ((1 << reg_width) - 1)))
+ goto out_err;
+ if (unlikely(!(direction & (DMA_TO_DEVICE | DMA_FROM_DEVICE))))
+ goto out_err;
+
+ retval = ERR_PTR(-ENOMEM);
+
+ if (periods > NR_DESCS_PER_CHANNEL)
+ goto out_err;
+
+ cdesc = kzalloc(sizeof(struct dw_cyclic_desc), GFP_KERNEL);
+ if (!cdesc)
+ goto out_err;
+
+ cdesc->desc = kzalloc(sizeof(struct dw_desc *) * periods, GFP_KERNEL);
+ if (!cdesc->desc)
+ goto out_err_alloc;
+
+ for (i = 0; i < periods; i++) {
+ desc = dwc_desc_get(dwc);
+ if (!desc)
+ goto out_err_desc_get;
+
+ switch (direction) {
+ case DMA_TO_DEVICE:
+ desc->lli.dar = dws->tx_reg;
+ desc->lli.sar = buf_addr + (period_len * i);
+ desc->lli.ctllo = (DWC_DEFAULT_CTLLO
+ | DWC_CTLL_DST_WIDTH(reg_width)
+ | DWC_CTLL_SRC_WIDTH(reg_width)
+ | DWC_CTLL_DST_FIX
+ | DWC_CTLL_SRC_INC
+ | DWC_CTLL_FC_M2P
+ | DWC_CTLL_INT_EN);
+ break;
+ case DMA_FROM_DEVICE:
+ desc->lli.dar = buf_addr + (period_len * i);
+ desc->lli.sar = dws->rx_reg;
+ desc->lli.ctllo = (DWC_DEFAULT_CTLLO
+ | DWC_CTLL_SRC_WIDTH(reg_width)
+ | DWC_CTLL_DST_WIDTH(reg_width)
+ | DWC_CTLL_DST_INC
+ | DWC_CTLL_SRC_FIX
+ | DWC_CTLL_FC_P2M
+ | DWC_CTLL_INT_EN);
+ break;
+ default:
+ break;
+ }
+
+ desc->lli.ctlhi = (period_len >> reg_width);
+ cdesc->desc[i] = desc;
+
+ if (last) {
+ last->lli.llp = desc->txd.phys;
+ dma_sync_single_for_device(chan2parent(chan),
+ last->txd.phys, sizeof(last->lli),
+ DMA_TO_DEVICE);
+ }
+
+ last = desc;
+ }
+
+ /* lets make a cyclic list */
+ last->lli.llp = cdesc->desc[0]->txd.phys;
+ dma_sync_single_for_device(chan2parent(chan), last->txd.phys,
+ sizeof(last->lli), DMA_TO_DEVICE);
+
+ dev_dbg(chan2dev(&dwc->chan), "cyclic prepared buf 0x%08x len %zu "
+ "period %zu periods %d\n", buf_addr, buf_len,
+ period_len, periods);
+
+ cdesc->periods = periods;
+ dwc->cdesc = cdesc;
+
+ return cdesc;
+
+out_err_desc_get:
+ while (i--)
+ dwc_desc_put(dwc, cdesc->desc[i]);
+out_err_alloc:
+ kfree(cdesc);
+out_err:
+ clear_bit(DW_DMA_IS_CYCLIC, &dwc->flags);
+ return (struct dw_cyclic_desc *)retval;
+}
+EXPORT_SYMBOL(dw_dma_cyclic_prep);
+
+void dw_dma_cyclic_free(struct dma_chan *chan)
+{
+ struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
+ struct dw_dma *dw = to_dw_dma(dwc->chan.device);
+ struct dw_cyclic_desc *cdesc = dwc->cdesc;
+ int i;
+
+ dev_dbg(chan2dev(&dwc->chan), "cyclic free\n");
+
+ if (!cdesc)
+ return;
+
+ spin_lock_bh(&dwc->lock);
+
+ channel_clear_bit(dw, CH_EN, dwc->mask);
+ while (dma_readl(dw, CH_EN) & dwc->mask)
+ cpu_relax();
+
+ dma_writel(dw, CLEAR.BLOCK, dwc->mask);
+ dma_writel(dw, CLEAR.ERROR, dwc->mask);
+ dma_writel(dw, CLEAR.XFER, dwc->mask);
+
+ spin_unlock_bh(&dwc->lock);
+
+ for (i = 0; i < cdesc->periods; i++)
+ dwc_desc_put(dwc, cdesc->desc[i]);
+
+ kfree(cdesc->desc);
+ kfree(cdesc);
+
+ clear_bit(DW_DMA_IS_CYCLIC, &dwc->flags);
+}
+EXPORT_SYMBOL(dw_dma_cyclic_free);
+
/*----------------------------------------------------------------------*/

static void dw_dma_off(struct dw_dma *dw)
diff --git a/drivers/dma/dw_dmac_regs.h b/drivers/dma/dw_dmac_regs.h
index b252b20..13a5807 100644
--- a/drivers/dma/dw_dmac_regs.h
+++ b/drivers/dma/dw_dmac_regs.h
@@ -126,6 +126,10 @@ struct dw_dma_regs {

#define DW_REGLEN 0x400

+enum dw_dmac_flags {
+ DW_DMA_IS_CYCLIC = 0,
+};
+
struct dw_dma_chan {
struct dma_chan chan;
void __iomem *ch_regs;
@@ -134,10 +138,12 @@ struct dw_dma_chan {
spinlock_t lock;

/* these other elements are all protected by lock */
+ unsigned long flags;
dma_cookie_t completed;
struct list_head active_list;
struct list_head queue;
struct list_head free_list;
+ struct dw_cyclic_desc *cdesc;

unsigned int descs_allocated;
};
@@ -158,7 +164,6 @@ static inline struct dw_dma_chan *to_dw_dma_chan(struct dma_chan *chan)
return container_of(chan, struct dw_dma_chan, chan);
}

-
struct dw_dma {
struct dma_device dma;
void __iomem *regs;
diff --git a/include/linux/dw_dmac.h b/include/linux/dw_dmac.h
index d797dde..c8aad71 100644
--- a/include/linux/dw_dmac.h
+++ b/include/linux/dw_dmac.h
@@ -74,4 +74,23 @@ struct dw_dma_slave {
#define DWC_CFGL_HS_DST_POL (1 << 18) /* dst handshake active low */
#define DWC_CFGL_HS_SRC_POL (1 << 19) /* src handshake active low */

+/* DMA API extensions */
+struct dw_cyclic_desc {
+ struct dw_desc **desc;
+ unsigned long periods;
+ void (*period_callback)(void *param);
+ void *period_callback_param;
+};
+
+struct dw_cyclic_desc *dw_dma_cyclic_prep(struct dma_chan *chan,
+ dma_addr_t buf_addr, size_t buf_len, size_t period_len,
+ enum dma_data_direction direction);
+void dw_dma_cyclic_free(struct dma_chan *chan);
+int dw_dma_cyclic_start(struct dma_chan *chan);
+void dw_dma_cyclic_stop(struct dma_chan *chan);
+
+dma_addr_t dw_dma_get_src_addr(struct dma_chan *chan);
+
+dma_addr_t dw_dma_get_dst_addr(struct dma_chan *chan);
+
#endif /* DW_DMAC_H */
--
1.5.6.3


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