spi: fsl-spi: Re-organise transfer bits_per_word adaptation

For different reasons, fsl-spi driver performs bits_per_word
modifications for different reasons:
- On CPU mode, to minimise amount of interrupts
- On CPM/QE mode to work around controller byte order

For CPU mode that's done in fsl_spi_prepare_message() while
for CPM mode that's done in fsl_spi_setup_transfer().

Reunify all of it in fsl_spi_prepare_message(), and catch
impossible cases early through master's bits_per_word_mask
instead of returning EINVAL later.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/r/0ce96fe96e8b07cba0613e4097cfd94d09b8919a.1680371809.git.christophe.leroy@csgroup.euSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-fsl-spi.c

@@ -177,26 +177,6 @@ static int mspi_apply_cpu_mode_quirks(struct spi_mpc8xxx_cs *cs,
 	return bits_per_word;
 }
 
-static int mspi_apply_qe_mode_quirks(struct spi_mpc8xxx_cs *cs,
-				struct spi_device *spi,
-				int bits_per_word)
-{
-	/* CPM/QE uses Little Endian for words > 8
-	 * so transform 16 and 32 bits words into 8 bits
-	 * Unfortnatly that doesn't work for LSB so
-	 * reject these for now */
-	/* Note: 32 bits word, LSB works iff
-	 * tfcr/rfcr is set to CPMFCR_GBL */
-	if (spi->mode & SPI_LSB_FIRST &&
-	    bits_per_word > 8)
-		return -EINVAL;
-	if (bits_per_word <= 8)
-		return bits_per_word;
-	if (bits_per_word == 16 || bits_per_word == 32)
-		return 8; /* pretend its 8 bits */
-	return -EINVAL;
-}
-
 static int fsl_spi_setup_transfer(struct spi_device *spi,
 					struct spi_transfer *t)
 {
@@ -224,9 +204,6 @@ static int fsl_spi_setup_transfer(struct spi_device *spi,
 		bits_per_word = mspi_apply_cpu_mode_quirks(cs, spi,
 							   mpc8xxx_spi,
 							   bits_per_word);
-	else
-		bits_per_word = mspi_apply_qe_mode_quirks(cs, spi,
-							  bits_per_word);
 
 	if (bits_per_word < 0)
 		return bits_per_word;
@@ -361,6 +338,19 @@ static int fsl_spi_prepare_message(struct spi_controller *ctlr,
 				t->bits_per_word = 32;
 			else if ((t->len & 1) == 0)
 				t->bits_per_word = 16;
+		} else {
+			/*
+			 * CPM/QE uses Little Endian for words > 8
+			 * so transform 16 and 32 bits words into 8 bits
+			 * Unfortnatly that doesn't work for LSB so
+			 * reject these for now
+			 * Note: 32 bits word, LSB works iff
+			 * tfcr/rfcr is set to CPMFCR_GBL
+			 */
+			if (m->spi->mode & SPI_LSB_FIRST && t->bits_per_word > 8)
+				return -EINVAL;
+			if (t->bits_per_word == 16 || t->bits_per_word == 32)
+				t->bits_per_word = 8; /* pretend its 8 bits */
 		}
 	}
 	return fsl_spi_setup_transfer(m->spi, first);
@@ -594,8 +584,14 @@ static struct spi_master *fsl_spi_probe(struct device *dev,
 	if (mpc8xxx_spi->type == TYPE_GRLIB)
 		fsl_spi_grlib_probe(dev);
 
-	master->bits_per_word_mask =
-		(SPI_BPW_RANGE_MASK(4, 16) | SPI_BPW_MASK(32)) &
+	if (mpc8xxx_spi->flags & SPI_CPM_MODE)
+		master->bits_per_word_mask =
+			(SPI_BPW_RANGE_MASK(4, 8) | SPI_BPW_MASK(16) | SPI_BPW_MASK(32));
+	else
+		master->bits_per_word_mask =
+			(SPI_BPW_RANGE_MASK(4, 16) | SPI_BPW_MASK(32));
+
+	master->bits_per_word_mask &=
 		SPI_BPW_RANGE_MASK(1, mpc8xxx_spi->max_bits_per_word);
 
 	if (mpc8xxx_spi->flags & SPI_QE_CPU_MODE)