dmaengine: hsu: Export hsu_dma_get_status()

To allow other code to safely read DMA Channel Status Register (where
the register attribute for Channel Error, Descriptor Time Out &
Descriptor Done fields are read-clear), export hsu_dma_get_status().
hsu_dma_irq() is renamed to hsu_dma_do_irq() and requires Status
Register value to be passed in.

Signed-off-by: Chuah, Kim Tatt <kim.tatt.chuah@intel.com>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 106 insertions, 31 deletions

diff --git a/drivers/dma/hsu/hsu.c b/drivers/dma/hsu/hsu.c
index f8c5cd53307c..c5f21efd6090 100644
--- a/drivers/dma/hsu/hsu.c
+++ b/drivers/dma/hsu/hsu.c
@@ -126,28 +126,33 @@ static void hsu_dma_start_transfer(struct hsu_dma_chan *hsuc)
         hsu_dma_start_channel(hsuc);
 }
 
-static u32 hsu_dma_chan_get_sr(struct hsu_dma_chan *hsuc)
-{
-        unsigned long flags;
-        u32 sr;
-
-        spin_lock_irqsave(&hsuc->vchan.lock, flags);
-        sr = hsu_chan_readl(hsuc, HSU_CH_SR);
-        spin_unlock_irqrestore(&hsuc->vchan.lock, flags);
-
-        return sr & ~(HSU_CH_SR_DESCE_ANY | HSU_CH_SR_CDESC_ANY);
-}
-
-irqreturn_t hsu_dma_irq(struct hsu_dma_chip *chip, unsigned short nr)
+/*
+ *      hsu_dma_get_status() - get DMA channel status
+ *      @chip: HSUART DMA chip
+ *      @nr: DMA channel number
+ *      @status: pointer for DMA Channel Status Register value
+ *
+ *      Description:
+ *      The function reads and clears the DMA Channel Status Register, checks
+ *      if it was a timeout interrupt and returns a corresponding value.
+ *
+ *      Caller should provide a valid pointer for the DMA Channel Status
+ *      Register value that will be returned in @status.
+ *
+ *      Return:
+ *      1 for DMA timeout status, 0 for other DMA status, or error code for
+ *      invalid parameters or no interrupt pending.
+ */
+int hsu_dma_get_status(struct hsu_dma_chip *chip, unsigned short nr,
+                       u32 *status)
 {
         struct hsu_dma_chan *hsuc;
-        struct hsu_dma_desc *desc;
         unsigned long flags;
         u32 sr;
 
         /* Sanity check */
         if (nr >= chip->hsu->nr_channels)
-                return IRQ_NONE;
+                return -EINVAL;
 
         hsuc = &chip->hsu->chan[nr];
 
@@ -155,22 +160,65 @@ irqreturn_t hsu_dma_irq(struct hsu_dma_chip *chip, unsigned short nr)
          * No matter what situation, need read clear the IRQ status
          * There is a bug, see Errata 5, HSD 2900918
          */
-        sr = hsu_dma_chan_get_sr(hsuc);
+        spin_lock_irqsave(&hsuc->vchan.lock, flags);
+        sr = hsu_chan_readl(hsuc, HSU_CH_SR);
+        spin_unlock_irqrestore(&hsuc->vchan.lock, flags);
+
+        /* Check if any interrupt is pending */
+        sr &= ~(HSU_CH_SR_DESCE_ANY | HSU_CH_SR_CDESC_ANY);
         if (!sr)
-                return IRQ_NONE;
+                return -EIO;
 
         /* Timeout IRQ, need wait some time, see Errata 2 */
         if (sr & HSU_CH_SR_DESCTO_ANY)
                 udelay(2);
 
+        /*
+         * At this point, at least one of Descriptor Time Out, Channel Error
+         * or Descriptor Done bits must be set. Clear the Descriptor Time Out
+         * bits and if sr is still non-zero, it must be channel error or
+         * descriptor done which are higher priority than timeout and handled
+         * in hsu_dma_do_irq(). Else, it must be a timeout.
+         */
         sr &= ~HSU_CH_SR_DESCTO_ANY;
-        if (!sr)
-                return IRQ_HANDLED;
+
+        *status = sr;
+
+        return sr ? 0 : 1;
+}
+EXPORT_SYMBOL_GPL(hsu_dma_get_status);
+
+/*
+ *      hsu_dma_do_irq() - DMA interrupt handler
+ *      @chip: HSUART DMA chip
+ *      @nr: DMA channel number
+ *      @status: Channel Status Register value
+ *
+ *      Description:
+ *      This function handles Channel Error and Descriptor Done interrupts.
+ *      This function should be called after determining that the DMA interrupt
+ *      is not a normal timeout interrupt, ie. hsu_dma_get_status() returned 0.
+ *
+ *      Return:
+ *      IRQ_NONE for invalid channel number, IRQ_HANDLED otherwise.
+ */
+irqreturn_t hsu_dma_do_irq(struct hsu_dma_chip *chip, unsigned short nr,
+                           u32 status)
+{
+        struct hsu_dma_chan *hsuc;
+        struct hsu_dma_desc *desc;
+        unsigned long flags;
+
+        /* Sanity check */
+        if (nr >= chip->hsu->nr_channels)
+                return IRQ_NONE;
+
+        hsuc = &chip->hsu->chan[nr];
 
         spin_lock_irqsave(&hsuc->vchan.lock, flags);
         desc = hsuc->desc;
         if (desc) {
-                if (sr & HSU_CH_SR_CHE) {
+                if (status & HSU_CH_SR_CHE) {
                         desc->status = DMA_ERROR;
                 } else if (desc->active < desc->nents) {
                         hsu_dma_start_channel(hsuc);
@@ -184,7 +232,7 @@ irqreturn_t hsu_dma_irq(struct hsu_dma_chip *chip, unsigned short nr)
 
         return IRQ_HANDLED;
 }
-EXPORT_SYMBOL_GPL(hsu_dma_irq);
+EXPORT_SYMBOL_GPL(hsu_dma_do_irq);
 
 static struct hsu_dma_desc *hsu_dma_alloc_desc(unsigned int nents)
 {
diff --git a/drivers/dma/hsu/pci.c b/drivers/dma/hsu/pci.c
index e2db76bd56d8..9916058531d9 100644
--- a/drivers/dma/hsu/pci.c
+++ b/drivers/dma/hsu/pci.c
@@ -27,13 +27,20 @@ static irqreturn_t hsu_pci_irq(int irq, void *dev)
 {
         struct hsu_dma_chip *chip = dev;
         u32 dmaisr;
+        u32 status;
         unsigned short i;
         irqreturn_t ret = IRQ_NONE;
+        int err;
 
         dmaisr = readl(chip->regs + HSU_PCI_DMAISR);
         for (i = 0; i < chip->hsu->nr_channels; i++) {
-                if (dmaisr & 0x1)
-                        ret |= hsu_dma_irq(chip, i);
+                if (dmaisr & 0x1) {
+                        err = hsu_dma_get_status(chip, i, &status);
+                        if (err > 0)
+                                ret |= IRQ_HANDLED;
+                        else if (err == 0)
+                                ret |= hsu_dma_do_irq(chip, i, status);
+                }
                 dmaisr >>= 1;
         }
 
diff --git a/drivers/tty/serial/8250/8250_mid.c b/drivers/tty/serial/8250/8250_mid.c
index 86379a79a6a3..b218ff528df7 100644
--- a/drivers/tty/serial/8250/8250_mid.c
+++ b/drivers/tty/serial/8250/8250_mid.c
@@ -97,12 +97,24 @@ static int dnv_handle_irq(struct uart_port *p)
 {
         struct mid8250 *mid = p->private_data;
         unsigned int fisr = serial_port_in(p, INTEL_MID_UART_DNV_FISR);
+        u32 status;
         int ret = IRQ_NONE;
-
-        if (fisr & BIT(2))
-                ret |= hsu_dma_irq(&mid->dma_chip, 1);
-        if (fisr & BIT(1))
-                ret |= hsu_dma_irq(&mid->dma_chip, 0);
+        int err;
+
+        if (fisr & BIT(2)) {
+                err = hsu_dma_get_status(&mid->dma_chip, 1, &status);
+                if (err > 0)
+                        ret |= IRQ_HANDLED;
+                else if (err == 0)
+                        ret |= hsu_dma_do_irq(&mid->dma_chip, 1, status);
+        }
+        if (fisr & BIT(1)) {
+                err = hsu_dma_get_status(&mid->dma_chip, 0, &status);
+                if (err > 0)
+                        ret |= IRQ_HANDLED;
+                else if (err == 0)
+                        ret |= hsu_dma_do_irq(&mid->dma_chip, 0, status);
+        }
         if (fisr & BIT(0))
                 ret |= serial8250_handle_irq(p, serial_port_in(p, UART_IIR));
         return ret;
diff --git a/include/linux/dma/hsu.h b/include/linux/dma/hsu.h
index 79df69dc629c..aaff68efba5d 100644
--- a/include/linux/dma/hsu.h
+++ b/include/linux/dma/hsu.h
@@ -39,14 +39,22 @@ struct hsu_dma_chip {
 
 #if IS_ENABLED(CONFIG_HSU_DMA)
 /* Export to the internal users */
-irqreturn_t hsu_dma_irq(struct hsu_dma_chip *chip, unsigned short nr);
+int hsu_dma_get_status(struct hsu_dma_chip *chip, unsigned short nr,
+                       u32 *status);
+irqreturn_t hsu_dma_do_irq(struct hsu_dma_chip *chip, unsigned short nr,
+                           u32 status);
 
 /* Export to the platform drivers */
 int hsu_dma_probe(struct hsu_dma_chip *chip);
 int hsu_dma_remove(struct hsu_dma_chip *chip);
 #else
-static inline irqreturn_t hsu_dma_irq(struct hsu_dma_chip *chip,
-                                      unsigned short nr)
+static inline int hsu_dma_get_status(struct hsu_dma_chip *chip,
+                                     unsigned short nr, u32 *status)
+{
+        return 0;
+}
+static inline irqreturn_t hsu_dma_do_irq(struct hsu_dma_chip *chip,
+                                         unsigned short nr, u32 status)
 {
         return IRQ_NONE;
 }