ASoC: davinci-mcasp: Correct RX start sequence

Follow the sequence described in the TRMs when starting RX.
Write to RXBUF register was not correct and there is no need to release the
RX state machine/Receive frame sync generator twice.
Signed-off-by: NPeter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

sound/soc/davinci/davinci-mcasp.c

@@ -154,9 +154,9 @@ static bool mcasp_is_synchronous(struct davinci_mcasp *mcasp)
 
 static void mcasp_start_rx(struct davinci_mcasp *mcasp)
 {
+	/* Start clocks */
 	mcasp_set_ctl_reg(mcasp, DAVINCI_MCASP_GBLCTLR_REG, RXHCLKRST);
 	mcasp_set_ctl_reg(mcasp, DAVINCI_MCASP_GBLCTLR_REG, RXCLKRST);
-
 	/*
 	 * When ASYNC == 0 the transmit and receive sections operate
 	 * synchronously from the transmit clock and frame sync. We need to make
@@ -167,16 +167,12 @@ static void mcasp_start_rx(struct davinci_mcasp *mcasp)
 		mcasp_set_ctl_reg(mcasp, DAVINCI_MCASP_GBLCTLX_REG, TXCLKRST);
 	}
 
+	/* Activate serializer(s) */
 	mcasp_set_ctl_reg(mcasp, DAVINCI_MCASP_GBLCTLR_REG, RXSERCLR);
-	mcasp_set_reg(mcasp, DAVINCI_MCASP_RXBUF_REG, 0);
-
-	mcasp_set_ctl_reg(mcasp, DAVINCI_MCASP_GBLCTLR_REG, RXSMRST);
-	mcasp_set_ctl_reg(mcasp, DAVINCI_MCASP_GBLCTLR_REG, RXFSRST);
-	mcasp_set_reg(mcasp, DAVINCI_MCASP_RXBUF_REG, 0);
-
+	/* Release RX state machine */
 	mcasp_set_ctl_reg(mcasp, DAVINCI_MCASP_GBLCTLR_REG, RXSMRST);
+	/* Release Frame Sync generator */
 	mcasp_set_ctl_reg(mcasp, DAVINCI_MCASP_GBLCTLR_REG, RXFSRST);
-
 	if (mcasp_is_synchronous(mcasp))
 		mcasp_set_ctl_reg(mcasp, DAVINCI_MCASP_GBLCTLX_REG, TXFSRST);
 }