USB: musb: Fix CPPI IRQs not being signaled

On tx channel abort a cppi interrupt is generated for a short time by
setting the lowest bit of the TCPPICOMPPTR register. It is then reset
immediately by clearing the bit. When the interrupt handler is run,
it does not detect an interrupt in the TCPPIMSKSR or RCPPIMSKSR
registers and thus exits early without writing the TCPPIEOIR register.
It appears that this inhibits further cppi interrupts until the handler
is called by chance, f.ex. from davinci_interrupt().

By moving the unmasking of the interrupt below the writes to
TCPPICOMPPTR, no interrupt is generated and no write to TCPPIEOIR is
necessary.
Signed-off-by: Daniel Glöckner <dg@emlix.com>
Signed-off-by: Ajay Kumar Gupta <ajay.gupta@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/musb/cppi_dma.c

@@ -1442,11 +1442,6 @@ static int cppi_channel_abort(struct dma_channel *channel)
 		musb_writew(regs, MUSB_TXCSR, value);
 		musb_writew(regs, MUSB_TXCSR, value);
 
-		/* re-enable interrupt */
-		if (enabled)
-			musb_writel(tibase, DAVINCI_TXCPPI_INTENAB_REG,
-					(1 << cppi_ch->index));
-
 		/* While we scrub the TX state RAM, ensure that we clean
 		 * up any interrupt that's currently asserted:
 		 * 1. Write to completion Ptr value 0x1(bit 0 set)
@@ -1459,6 +1454,11 @@ static int cppi_channel_abort(struct dma_channel *channel)
 		cppi_reset_tx(tx_ram, 1);
 		musb_writel(&tx_ram->tx_complete, 0, 0);
 
+		/* re-enable interrupt */
+		if (enabled)
+			musb_writel(tibase, DAVINCI_TXCPPI_INTENAB_REG,
+					(1 << cppi_ch->index));
+
 		cppi_dump_tx(5, cppi_ch, " (done teardown)");
 
 		/* REVISIT tx side _should_ clean up the same way