ASoC: fsl_sai: Improve fsl_sai_isr()

This patch improves fsl_sai_isr() in these ways:
1, Add comment for mask fetching code.
2, Return IRQ_NONE if the IRQ is not for the device.
3, Use regmap_write() instead of regmap_update_bits().

Signed-off-by: Nicolin Chen <Guangyu.Chen@freescale.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

1 files changed, 45 insertions, 19 deletions

diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
index 56da8c8c5960..7194d9280020 100644
--- a/sound/soc/fsl/fsl_sai.c
+++ b/sound/soc/fsl/fsl_sai.c
@@ -30,62 +30,88 @@ static irqreturn_t fsl_sai_isr(int irq, void *devid)
 {
         struct fsl_sai *sai = (struct fsl_sai *)devid;
         struct device *dev = &sai->pdev->dev;
-        u32 xcsr, mask;
+        u32 flags, xcsr, mask;
+        bool irq_none = true;
 
-        /* Only handle those what we enabled */
+        /*
+         * Both IRQ status bits and IRQ mask bits are in the xCSR but
+         * different shifts. And we here create a mask only for those
+         * IRQs that we activated.
+         */
         mask = (FSL_SAI_FLAGS >> FSL_SAI_CSR_xIE_SHIFT) << FSL_SAI_CSR_xF_SHIFT;
 
         /* Tx IRQ */
         regmap_read(sai->regmap, FSL_SAI_TCSR, &xcsr);
-        xcsr &= mask;
+        flags = xcsr & mask;
 
-        if (xcsr & FSL_SAI_CSR_WSF)
+        if (flags)
+                irq_none = false;
+        else
+                goto irq_rx;
+
+        if (flags & FSL_SAI_CSR_WSF)
                 dev_dbg(dev, "isr: Start of Tx word detected\n");
 
-        if (xcsr & FSL_SAI_CSR_SEF)
+        if (flags & FSL_SAI_CSR_SEF)
                 dev_warn(dev, "isr: Tx Frame sync error detected\n");
 
-        if (xcsr & FSL_SAI_CSR_FEF) {
+        if (flags & FSL_SAI_CSR_FEF) {
                 dev_warn(dev, "isr: Transmit underrun detected\n");
                 /* FIFO reset for safety */
                 xcsr |= FSL_SAI_CSR_FR;
         }
 
-        if (xcsr & FSL_SAI_CSR_FWF)
+        if (flags & FSL_SAI_CSR_FWF)
                 dev_dbg(dev, "isr: Enabled transmit FIFO is empty\n");
 
-        if (xcsr & FSL_SAI_CSR_FRF)
+        if (flags & FSL_SAI_CSR_FRF)
                 dev_dbg(dev, "isr: Transmit FIFO watermark has been reached\n");
 
-        regmap_update_bits(sai->regmap, FSL_SAI_TCSR,
-                           FSL_SAI_CSR_xF_W_MASK | FSL_SAI_CSR_FR, xcsr);
+        flags &= FSL_SAI_CSR_xF_W_MASK;
+        xcsr &= ~FSL_SAI_CSR_xF_MASK;
+
+        if (flags)
+                regmap_write(sai->regmap, FSL_SAI_TCSR, flags | xcsr);
 
+irq_rx:
         /* Rx IRQ */
         regmap_read(sai->regmap, FSL_SAI_RCSR, &xcsr);
-        xcsr &= mask;
+        flags = xcsr & mask;
 
-        if (xcsr & FSL_SAI_CSR_WSF)
+        if (flags)
+                irq_none = false;
+        else
+                goto out;
+
+        if (flags & FSL_SAI_CSR_WSF)
                 dev_dbg(dev, "isr: Start of Rx word detected\n");
 
-        if (xcsr & FSL_SAI_CSR_SEF)
+        if (flags & FSL_SAI_CSR_SEF)
                 dev_warn(dev, "isr: Rx Frame sync error detected\n");
 
-        if (xcsr & FSL_SAI_CSR_FEF) {
+        if (flags & FSL_SAI_CSR_FEF) {
                 dev_warn(dev, "isr: Receive overflow detected\n");
                 /* FIFO reset for safety */
                 xcsr |= FSL_SAI_CSR_FR;
         }
 
-        if (xcsr & FSL_SAI_CSR_FWF)
+        if (flags & FSL_SAI_CSR_FWF)
                 dev_dbg(dev, "isr: Enabled receive FIFO is full\n");
 
-        if (xcsr & FSL_SAI_CSR_FRF)
+        if (flags & FSL_SAI_CSR_FRF)
                 dev_dbg(dev, "isr: Receive FIFO watermark has been reached\n");
 
-        regmap_update_bits(sai->regmap, FSL_SAI_RCSR,
-                           FSL_SAI_CSR_xF_W_MASK | FSL_SAI_CSR_FR, xcsr);
+        flags &= FSL_SAI_CSR_xF_W_MASK;
+        xcsr &= ~FSL_SAI_CSR_xF_MASK;
 
-        return IRQ_HANDLED;
+        if (flags)
+                regmap_write(sai->regmap, FSL_SAI_TCSR, flags | xcsr);
+
+out:
+        if (irq_none)
+                return IRQ_NONE;
+        else
+                return IRQ_HANDLED;
 }
 
 static int fsl_sai_set_dai_sysclk_tr(struct snd_soc_dai *cpu_dai,