OMAP3 SPI : Fixed bugs related to SPI transfer

Added posted writes (read after writes) to effect the
change immediately for channel confiuration and channel
enable register

Disable the channel to purge receieve data in TX_ONLY
mode transfer otherwise rx data will get affected by
the next immediate RX_ONLY mode transfer

Wait for the EOT bit to be set after last byte has been
loaded to TX shift register in the the TX_ONLY mode.This
ensures TX data has been completely shifted out

Disable the channel in RX_ONLY mode before reading the
last data from  RXX register to prevent the SPI slave
to transmit next word

Signed-off-by: Ajoy Kumar Das <akdas75@yahoo.in>
Cc: Tom Rini <trini@ti.com>
Cc: jacopo mondi <j.mondi@voltaelectronics.com>

drivers/spi/omap3_spi.c

@@ -57,6 +57,20 @@ static void spi_reset(struct omap3_spi_slave *ds)
 	writel(OMAP3_MCSPI_WAKEUPENABLE_WKEN, &ds->regs->wakeupenable);
 }
 
+static void omap3_spi_write_chconf(struct omap3_spi_slave *ds, int val)
+{
+	writel(val, &ds->regs->channel[ds->slave.cs].chconf);
+	/* Flash post writes to make immediate effect */
+	readl(&ds->regs->channel[ds->slave.cs].chconf);
+}
+
+static void omap3_spi_set_enable(struct omap3_spi_slave *ds, int enable)
+{
+	writel(enable, &ds->regs->channel[ds->slave.cs].chctrl);
+        /* Flash post writes to make immediate effect */
+	readl(&ds->regs->channel[ds->slave.cs].chctrl);
+}
+
 void spi_init()
 {
 	/* do nothing */
@@ -212,7 +226,7 @@ int spi_claim_bus(struct spi_slave *slave)
 	/* Transmit & receive mode */
 	conf &= ~OMAP3_MCSPI_CHCONF_TRM_MASK;
 
-	writel(conf, &ds->regs->channel[ds->slave.cs].chconf);
+	omap3_spi_write_chconf(ds,conf);
 
 	return 0;
 }
@@ -233,14 +247,13 @@ int omap3_spi_write(struct spi_slave *slave, unsigned int len, const u8 *txp,
 	int timeout = SPI_WAIT_TIMEOUT;
 	int chconf = readl(&ds->regs->channel[ds->slave.cs].chconf);
 
-	if (flags & SPI_XFER_BEGIN)
-		writel(OMAP3_MCSPI_CHCTRL_EN,
-		       &ds->regs->channel[ds->slave.cs].chctrl);
+	/* Enable the channel */
+	omap3_spi_set_enable(ds,OMAP3_MCSPI_CHCTRL_EN);
 
 	chconf &= ~OMAP3_MCSPI_CHCONF_TRM_MASK;
 	chconf |= OMAP3_MCSPI_CHCONF_TRM_TX_ONLY;
 	chconf |= OMAP3_MCSPI_CHCONF_FORCE;
-	writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);
+	omap3_spi_write_chconf(ds,chconf);
 
 	for (i = 0; i < len; i++) {
 		/* wait till TX register is empty (TXS == 1) */
@@ -256,15 +269,17 @@ int omap3_spi_write(struct spi_slave *slave, unsigned int len, const u8 *txp,
 		writel(txp[i], &ds->regs->channel[ds->slave.cs].tx);
 	}
 
+        /* wait to finish of transfer */
+        while (!(readl(&ds->regs->channel[ds->slave.cs].chstat) &
+                         OMAP3_MCSPI_CHSTAT_EOT));
+
+	/* Disable the channel otherwise the next immediate RX will get affected */
+	omap3_spi_set_enable(ds,OMAP3_MCSPI_CHCTRL_DIS);
+
 	if (flags & SPI_XFER_END) {
-		/* wait to finish of transfer */
-		while (!(readl(&ds->regs->channel[ds->slave.cs].chstat) &
-			 OMAP3_MCSPI_CHSTAT_EOT));
 
 		chconf &= ~OMAP3_MCSPI_CHCONF_FORCE;
-		writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);
-
-		writel(0, &ds->regs->channel[ds->slave.cs].chctrl);
+		omap3_spi_write_chconf(ds,chconf);
 	}
 	return 0;
 }
@@ -277,14 +292,13 @@ int omap3_spi_read(struct spi_slave *slave, unsigned int len, u8 *rxp,
 	int timeout = SPI_WAIT_TIMEOUT;
 	int chconf = readl(&ds->regs->channel[ds->slave.cs].chconf);
 
-	if (flags & SPI_XFER_BEGIN)
-		writel(OMAP3_MCSPI_CHCTRL_EN,
-		       &ds->regs->channel[ds->slave.cs].chctrl);
+	/* Enable the channel */
+	omap3_spi_set_enable(ds,OMAP3_MCSPI_CHCTRL_EN);
 
 	chconf &= ~OMAP3_MCSPI_CHCONF_TRM_MASK;
 	chconf |= OMAP3_MCSPI_CHCONF_TRM_RX_ONLY;
 	chconf |= OMAP3_MCSPI_CHCONF_FORCE;
-	writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);
+	omap3_spi_write_chconf(ds,chconf);
 
 	writel(0, &ds->regs->channel[ds->slave.cs].tx);
 
@@ -298,15 +312,18 @@ int omap3_spi_read(struct spi_slave *slave, unsigned int len, u8 *rxp,
 				return -1;
 			}
 		}
+
+		/* Disable the channel to prevent furher receiving */
+		if(i == (len - 1))
+			omap3_spi_set_enable(ds,OMAP3_MCSPI_CHCTRL_DIS);
+
 		/* Read the data */
 		rxp[i] = readl(&ds->regs->channel[ds->slave.cs].rx);
 	}
 
 	if (flags & SPI_XFER_END) {
 		chconf &= ~OMAP3_MCSPI_CHCONF_FORCE;
-		writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);
-
-		writel(0, &ds->regs->channel[ds->slave.cs].chctrl);
+		omap3_spi_write_chconf(ds,chconf);
 	}
 
 	return 0;
@@ -323,14 +340,12 @@ int omap3_spi_txrx(struct spi_slave *slave,
 	int i=0;
 
 	/*Enable SPI channel*/
-	if (flags & SPI_XFER_BEGIN)
-		writel(OMAP3_MCSPI_CHCTRL_EN,
-		       &ds->regs->channel[ds->slave.cs].chctrl);
+	omap3_spi_set_enable(ds,OMAP3_MCSPI_CHCTRL_EN);
 
 	/*set TRANSMIT-RECEIVE Mode*/
 	chconf &= ~OMAP3_MCSPI_CHCONF_TRM_MASK;
 	chconf |= OMAP3_MCSPI_CHCONF_FORCE;
-	writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);
+	omap3_spi_write_chconf(ds,chconf);
 
 	/*Shift in and out 1 byte at time*/
 	for (i=0; i < len; i++){
@@ -359,13 +374,13 @@ int omap3_spi_txrx(struct spi_slave *slave,
 		/* Read the data */
 		rxp[i] = readl(&ds->regs->channel[ds->slave.cs].rx);
 	}
+	/* Disable the channel */
+        omap3_spi_set_enable(ds,OMAP3_MCSPI_CHCTRL_DIS);
 
 	/*if transfer must be terminated disable the channel*/
 	if (flags & SPI_XFER_END) {
 		chconf &= ~OMAP3_MCSPI_CHCONF_FORCE;
-		writel(chconf, &ds->regs->channel[ds->slave.cs].chconf);
-
-		writel(0, &ds->regs->channel[ds->slave.cs].chctrl);
+		omap3_spi_write_chconf(ds,chconf);
 	}
 
 	return 0;
@@ -389,17 +404,14 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
 		int chconf = readl(&ds->regs->channel[ds->slave.cs].chconf);
 
 		if (flags & SPI_XFER_BEGIN) {
-			writel(OMAP3_MCSPI_CHCTRL_EN,
-			       &ds->regs->channel[ds->slave.cs].chctrl);
+			omap3_spi_set_enable(ds,OMAP3_MCSPI_CHCTRL_EN);
 			chconf |= OMAP3_MCSPI_CHCONF_FORCE;
-			writel(chconf,
-			       &ds->regs->channel[ds->slave.cs].chconf);
+			omap3_spi_write_chconf(ds,chconf);
 		}
 		if (flags & SPI_XFER_END) {
 			chconf &= ~OMAP3_MCSPI_CHCONF_FORCE;
-			writel(chconf,
-			       &ds->regs->channel[ds->slave.cs].chconf);
-			writel(0, &ds->regs->channel[ds->slave.cs].chctrl);
+			omap3_spi_write_chconf(ds,chconf);
+			omap3_spi_set_enable(ds,OMAP3_MCSPI_CHCTRL_DIS);
 		}
 		ret = 0;
 	} else {

drivers/spi/omap3_spi.h

@@ -99,6 +99,7 @@ struct mcspi {
 #define OMAP3_MCSPI_CHSTAT_EOT		(1 << 2)
 
 #define OMAP3_MCSPI_CHCTRL_EN		(1 << 0)
+#define OMAP3_MCSPI_CHCTRL_DIS		(0 << 0)
 
 #define OMAP3_MCSPI_WAKEUPENABLE_WKEN	(1 << 0)