usb: musb: workaround MUSB DMA_INTR sometimes reads zero

MUSB DMA_INTR register may sometimes read zero when infact there
was a pending interrupt. Workaround this by reading the DMA_COUNT
values for all enabled channels when this condition occurs.
Flag these channels as the ones needing to be serviced.

Additionally, the absence of a debug print meant we would never
catch a spurious DMA interrupt in MUSB. So this patch adds a
debug print in the IRQ handler.

Signed-off-by: Anand Gadiyar <gadiyar@ti.com>
Cc: Ajay Kumar Gupta <ajay.gupta@ti.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Vikram Pandita <vikram.pandita@ti.com>
Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 22 insertions, 3 deletions

diff --git a/drivers/usb/musb/musbhsdma.c b/drivers/usb/musb/musbhsdma.c
index a237550f91bf..2fa7d5c00f31 100644
--- a/drivers/usb/musb/musbhsdma.c
+++ b/drivers/usb/musb/musbhsdma.c
@@ -250,20 +250,39 @@ static irqreturn_t dma_controller_irq(int irq, void *private_data)
         u8 bchannel;
         u8 int_hsdma;
 
-        u32 addr;
+        u32 addr, count;
         u16 csr;
 
         spin_lock_irqsave(&musb->lock, flags);
 
         int_hsdma = musb_readb(mbase, MUSB_HSDMA_INTR);
-        if (!int_hsdma)
-                goto done;
 
 #ifdef CONFIG_BLACKFIN
         /* Clear DMA interrupt flags */
         musb_writeb(mbase, MUSB_HSDMA_INTR, int_hsdma);
 #endif
 
+        if (!int_hsdma) {
+                DBG(2, "spurious DMA irq\n");
+
+                for (bchannel = 0; bchannel < MUSB_HSDMA_CHANNELS; bchannel++) {
+                        musb_channel = (struct musb_dma_channel *)
+                                        &(controller->channel[bchannel]);
+                        channel = &musb_channel->channel;
+                        if (channel->status == MUSB_DMA_STATUS_BUSY) {
+                                count = musb_read_hsdma_count(mbase, bchannel);
+
+                                if (count == 0)
+                                        int_hsdma |= (1 << bchannel);
+                        }
+                }
+
+                DBG(2, "int_hsdma = 0x%x\n", int_hsdma);
+
+                if (!int_hsdma)
+                        goto done;
+        }
+
         for (bchannel = 0; bchannel < MUSB_HSDMA_CHANNELS; bchannel++) {
                 if (int_hsdma & (1 << bchannel)) {
                         musb_channel = (struct musb_dma_channel *)