linux-kernel - [PATCH v1 1/5] spi: fsl-spi: Fix CPM/QE mode Litte Endian

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Date:   Sat,  1 Apr 2023 19:59:46 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Mark Brown <broonie@...nel.org>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Grant Likely <grant.likely@...retlab.ca>,
        Anton Vorontsov <cbouatmailru@...il.com>,
        Joakim Tjernlund <Joakim.Tjernlund@...nsmode.se>,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Joakim Tjernlund <Joakim.Tjernlund@...inera.com>
Subject: [PATCH v1 1/5] spi: fsl-spi: Fix CPM/QE mode Litte Endian

CPM has the same problem as QE so for CPM also use the fix added
by commit 0398fb70940e ("spi/spi_mpc8xxx: Fix QE mode Litte Endian"):

  CPM mode uses Little Endian so words > 8 bits are byte swapped.
  Workaround this by always enforcing wordsize 8 for 16 and 32 bits
  words. Unfortunately this will not work for LSB transfers
  where wordsize is > 8 bits so disable these for now.

Also limit the workaround to 16 and 32 bits words because it can
only work for multiples of 8-bits.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Joakim Tjernlund <Joakim.Tjernlund@...inera.com>
Fixes: 0398fb70940e ("spi/spi_mpc8xxx: Fix QE mode Litte Endian")
---
 drivers/spi/spi-fsl-spi.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/spi/spi-fsl-spi.c b/drivers/spi/spi-fsl-spi.c
index 93152144fd2e..5602f052b2b5 100644
--- a/drivers/spi/spi-fsl-spi.c
+++ b/drivers/spi/spi-fsl-spi.c
@@ -181,8 +181,8 @@ static int mspi_apply_qe_mode_quirks(struct spi_mpc8xxx_cs *cs,
 				struct spi_device *spi,
 				int bits_per_word)
 {
-	/* QE uses Little Endian for words > 8
-	 * so transform all words > 8 into 8 bits
+	/* 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
@@ -190,9 +190,11 @@ static int mspi_apply_qe_mode_quirks(struct spi_mpc8xxx_cs *cs,
 	if (spi->mode & SPI_LSB_FIRST &&
 	    bits_per_word > 8)
 		return -EINVAL;
-	if (bits_per_word > 8)
+	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 bits_per_word;
+	return -EINVAL;
 }
 
 static int fsl_spi_setup_transfer(struct spi_device *spi,
@@ -222,7 +224,7 @@ 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 if (mpc8xxx_spi->flags & SPI_QE)
+	else
 		bits_per_word = mspi_apply_qe_mode_quirks(cs, spi,
 							  bits_per_word);
 
-- 
2.39.2