spi: tegra20_slink: accept any word length

Original t20 slink could work with commands only
fully divisible by 8. This patch removes such
restriction, so commands of any bitlength now
can be passed and processed.

Tested-by: Andreas Westman Dorcsak <hedmoo@yahoo.com> # ASUS TF600T T30
Tested-by: Svyatoslav Ryhel <clamor95@gmail.com> # LG P895 T30
Tested-by: Thierry Reding <treding@nvidia.com> # T30 and T124
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
Signed-off-by: Tom <twarren@nvidia.com>

drivers/spi/tegra20_slink.c

@@ -208,16 +208,14 @@ static int tegra30_spi_xfer(struct udevice *dev, unsigned int bitlen,
 	u32 reg, tmpdout, tmpdin = 0;
 	const u8 *dout = data_out;
 	u8 *din = data_in;
-	int num_bytes;
-	int ret;
+	int num_bytes, overflow;
+	int ret = 0;
 
 	debug("%s: slave %u:%u dout %p din %p bitlen %u\n",
 	      __func__, dev_seq(bus), spi_chip_select(dev), dout, din, bitlen);
-	if (bitlen % 8)
-		return -1;
-	num_bytes = bitlen / 8;
 
-	ret = 0;
+	num_bytes = DIV_ROUND_UP(bitlen, 8);
+	overflow = bitlen % 8;
 
 	reg = readl(&regs->status);
 	writel(reg, &regs->status);	/* Clear all SPI events via R/W */
@@ -254,8 +252,13 @@ static int tegra30_spi_xfer(struct udevice *dev, unsigned int bitlen,
 
 		num_bytes -= bytes;
 
-		clrsetbits_le32(&regs->command, SLINK_CMD_BIT_LENGTH_MASK,
-				bytes * 8 - 1);
+		if (overflow && !num_bytes)
+			clrsetbits_le32(&regs->command, SLINK_CMD_BIT_LENGTH_MASK,
+					(bytes - 1) * 8 + overflow - 1);
+		else
+			clrsetbits_le32(&regs->command, SLINK_CMD_BIT_LENGTH_MASK,
+					bytes * 8 - 1);
+
 		writel(tmpdout, &regs->tx_fifo);
 		setbits_le32(&regs->command, SLINK_CMD_GO);