mxs-dma: enable CLKGATE before accessing registers

After calling mxs_dma_disable_chan() for a channel, that channel
becomes unusable because some controller registers can only be written
when the clock is enabled via CLKGATE.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c
index be641cb..b4588bd 100644 (file)
--- a/drivers/dma/mxs-dma.c
+++ b/drivers/dma/mxs-dma.c
@@ -130,6 +130,23 @@ struct mxs_dma_engine {
        struct mxs_dma_chan             mxs_chans[MXS_DMA_CHANNELS];
 };
 
+static inline void mxs_dma_clkgate(struct mxs_dma_chan *mxs_chan, int enable)
+{
+       struct mxs_dma_engine *mxs_dma = mxs_chan->mxs_dma;
+       int chan_id = mxs_chan->chan.chan_id;
+       int set_clr = enable ? MXS_CLR_ADDR : MXS_SET_ADDR;
+
+       /* enable apbh channel clock */
+       if (dma_is_apbh()) {
+               if (apbh_is_old())
+                       writel(1 << (chan_id + BP_APBH_CTRL0_CLKGATE_CHANNEL),
+                               mxs_dma->base + HW_APBHX_CTRL0 + set_clr);
+               else
+                       writel(1 << chan_id,
+                               mxs_dma->base + HW_APBHX_CTRL0 + set_clr);
+       }
+}
+
 static void mxs_dma_reset_chan(struct mxs_dma_chan *mxs_chan)
 {
        struct mxs_dma_engine *mxs_dma = mxs_chan->mxs_dma;
@@ -148,38 +165,21 @@ static void mxs_dma_enable_chan(struct mxs_dma_chan *mxs_chan)
        struct mxs_dma_engine *mxs_dma = mxs_chan->mxs_dma;
        int chan_id = mxs_chan->chan.chan_id;
 
+       /* clkgate needs to be enabled before writing other registers */
+       mxs_dma_clkgate(mxs_chan, 1);
+
        /* set cmd_addr up */
        writel(mxs_chan->ccw_phys,
                mxs_dma->base + HW_APBHX_CHn_NXTCMDAR(chan_id));
 
-       /* enable apbh channel clock */
-       if (dma_is_apbh()) {
-               if (apbh_is_old())
-                       writel(1 << (chan_id + BP_APBH_CTRL0_CLKGATE_CHANNEL),
-                               mxs_dma->base + HW_APBHX_CTRL0 + MXS_CLR_ADDR);
-               else
-                       writel(1 << chan_id,
-                               mxs_dma->base + HW_APBHX_CTRL0 + MXS_CLR_ADDR);
-       }
-
        /* write 1 to SEMA to kick off the channel */
        writel(1, mxs_dma->base + HW_APBHX_CHn_SEMA(chan_id));
 }
 
 static void mxs_dma_disable_chan(struct mxs_dma_chan *mxs_chan)
 {
-       struct mxs_dma_engine *mxs_dma = mxs_chan->mxs_dma;
-       int chan_id = mxs_chan->chan.chan_id;
-
        /* disable apbh channel clock */
-       if (dma_is_apbh()) {
-               if (apbh_is_old())
-                       writel(1 << (chan_id + BP_APBH_CTRL0_CLKGATE_CHANNEL),
-                               mxs_dma->base + HW_APBHX_CTRL0 + MXS_SET_ADDR);
-               else
-                       writel(1 << chan_id,
-                               mxs_dma->base + HW_APBHX_CTRL0 + MXS_SET_ADDR);
-       }
+       mxs_dma_clkgate(mxs_chan, 0);
 
        mxs_chan->status = DMA_SUCCESS;
 }
@@ -338,7 +338,10 @@ static int mxs_dma_alloc_chan_resources(struct dma_chan *chan)
        if (ret)
                goto err_clk;
 
+       /* clkgate needs to be enabled for reset to finish */
+       mxs_dma_clkgate(mxs_chan, 1);
        mxs_dma_reset_chan(mxs_chan);
+       mxs_dma_clkgate(mxs_chan, 0);
 
        dma_async_tx_descriptor_init(&mxs_chan->desc, chan);
        mxs_chan->desc.tx_submit = mxs_dma_tx_submit;