dw_dmac: add cyclic API to DW DMA driver

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>
Acked-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

3 files changed, 356 insertions, 2 deletions

diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
index 862fc9ce9d86..0b8aada08aa8 100644
--- a/drivers/dma/dw_dmac.c
+++ b/drivers/dma/dw_dmac.c
@@ -363,6 +363,82 @@ 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 DMAC 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);
+        }
+}
+
+/* ------------------------------------------------------------------------- */
+
 static void dw_dma_tasklet(unsigned long data)
 {
         struct dw_dma *dw = (struct dw_dma *)data;
@@ -382,7 +458,10 @@ 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);
@@ -883,6 +962,257 @@ static void dwc_free_chan_resources(struct dma_chan *chan)
         dev_vdbg(chan2dev(chan), "free_chan_resources done\n");
 }
 
+/* --------------------- Cyclic DMA API extensions -------------------- */
+
+/**
+ * dw_dma_cyclic_start - start the cyclic DMA transfer
+ * @chan: the DMA channel to start
+ *
+ * Must be called with soft interrupts disabled. Returns zero on success or
+ * -errno on failure.
+ */
+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);
+
+/**
+ * dw_dma_cyclic_stop - stop the cyclic DMA transfer
+ * @chan: the DMA channel to stop
+ *
+ * Must be called with soft interrupts disabled.
+ */
+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);
+
+        spin_lock(&dwc->lock);
+
+        channel_clear_bit(dw, CH_EN, dwc->mask);
+        while (dma_readl(dw, CH_EN) & dwc->mask)
+                cpu_relax();
+
+        spin_unlock(&dwc->lock);
+}
+EXPORT_SYMBOL(dw_dma_cyclic_stop);
+
+/**
+ * dw_dma_cyclic_prep - prepare the cyclic DMA transfer
+ * @chan: the DMA channel to prepare
+ * @buf_addr: physical DMA address where the buffer starts
+ * @buf_len: total number of bytes for the entire buffer
+ * @period_len: number of bytes for each period
+ * @direction: transfer direction, to or from device
+ *
+ * Must be called before trying to start the transfer. Returns a valid struct
+ * dw_cyclic_desc if successful or an ERR_PTR(-errno) if not successful.
+ */
+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);
+        spin_unlock_bh(&dwc->lock);
+        if (was_cyclic) {
+                dev_dbg(chan2dev(&dwc->chan),
+                                "channel already prepared for cyclic DMA\n");
+                return ERR_PTR(-EBUSY);
+        }
+
+        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);
+
+/**
+ * dw_dma_cyclic_free - free a prepared cyclic DMA transfer
+ * @chan: the DMA channel to free
+ */
+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 b252b202c5cf..13a580767031 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 d797dde247f7..c8aad713a046 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 */