dmaengine/dw_dmac: implement pause and resume in dwc_control

Some peripherals like amba-pl011 needs pause to be implemented in DMA controller
drivers. This also returns correct status from dwc_tx_status() in case chan is
paused.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

2 files changed, 40 insertions, 20 deletions

diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
index 442b98b81e7c..eec675bf4f95 100644
--- a/drivers/dma/dw_dmac.c
+++ b/drivers/dma/dw_dmac.c
@@ -862,34 +862,50 @@ static int dwc_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
         struct dw_dma           *dw = to_dw_dma(chan->device);
         struct dw_desc          *desc, *_desc;
         unsigned long           flags;
+        u32                     cfglo;
         LIST_HEAD(list);
 
-        /* Only supports DMA_TERMINATE_ALL */
-        if (cmd != DMA_TERMINATE_ALL)
-                return -ENXIO;
+        if (cmd == DMA_PAUSE) {
+                spin_lock_irqsave(&dwc->lock, flags);
 
-        /*
-         * This is only called when something went wrong elsewhere, so
-         * we don't really care about the data. Just disable the
-         * channel. We still have to poll the channel enable bit due
-         * to AHB/HSB limitations.
-         */
-        spin_lock_irqsave(&dwc->lock, flags);
+                cfglo = channel_readl(dwc, CFG_LO);
+                channel_writel(dwc, CFG_LO, cfglo | DWC_CFGL_CH_SUSP);
+                while (!(channel_readl(dwc, CFG_LO) & DWC_CFGL_FIFO_EMPTY))
+                        cpu_relax();
 
-        channel_clear_bit(dw, CH_EN, dwc->mask);
+                dwc->paused = true;
+                spin_unlock_irqrestore(&dwc->lock, flags);
+        } else if (cmd == DMA_RESUME) {
+                if (!dwc->paused)
+                        return 0;
 
-        while (dma_readl(dw, CH_EN) & dwc->mask)
-                cpu_relax();
+                spin_lock_irqsave(&dwc->lock, flags);
 
-        /* active_list entries will end up before queued entries */
-        list_splice_init(&dwc->queue, &list);
-        list_splice_init(&dwc->active_list, &list);
+                cfglo = channel_readl(dwc, CFG_LO);
+                channel_writel(dwc, CFG_LO, cfglo & ~DWC_CFGL_CH_SUSP);
+                dwc->paused = false;
 
-        spin_unlock_irqrestore(&dwc->lock, flags);
+                spin_unlock_irqrestore(&dwc->lock, flags);
+        } else if (cmd == DMA_TERMINATE_ALL) {
+                spin_lock_irqsave(&dwc->lock, flags);
 
-        /* Flush all pending and queued descriptors */
-        list_for_each_entry_safe(desc, _desc, &list, desc_node)
-                dwc_descriptor_complete(dwc, desc, false);
+                channel_clear_bit(dw, CH_EN, dwc->mask);
+                while (dma_readl(dw, CH_EN) & dwc->mask)
+                        cpu_relax();
+
+                dwc->paused = false;
+
+                /* active_list entries will end up before queued entries */
+                list_splice_init(&dwc->queue, &list);
+                list_splice_init(&dwc->active_list, &list);
+
+                spin_unlock_irqrestore(&dwc->lock, flags);
+
+                /* Flush all pending and queued descriptors */
+                list_for_each_entry_safe(desc, _desc, &list, desc_node)
+                        dwc_descriptor_complete(dwc, desc, false);
+        } else
+                return -ENXIO;
 
         return 0;
 }
@@ -923,6 +939,9 @@ dwc_tx_status(struct dma_chan *chan,
         else
                 dma_set_tx_state(txstate, last_complete, last_used, 0);
 
+        if (dwc->paused)
+                return DMA_PAUSED;
+
         return ret;
 }
 
diff --git a/drivers/dma/dw_dmac_regs.h b/drivers/dma/dw_dmac_regs.h
index 720f821527f8..c968597c32ab 100644
--- a/drivers/dma/dw_dmac_regs.h
+++ b/drivers/dma/dw_dmac_regs.h
@@ -138,6 +138,7 @@ struct dw_dma_chan {
         void __iomem            *ch_regs;
         u8                      mask;
         u8                      priority;
+        bool                    paused;
 
         spinlock_t              lock;