spi/spi_mpc8xxx: Fix QE mode Litte Endian

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

Also move the different quirks into its own function to keep
mpc8xxx_spi_setup_transfer() sane.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Acked-by: Anton Vorontsov <cbouatmailru@gmail.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 70 insertions, 31 deletions

diff --git a/drivers/spi/spi_mpc8xxx.c b/drivers/spi/spi_mpc8xxx.c
index 0dfc482bbff5..66517ce750f3 100644
--- a/drivers/spi/spi_mpc8xxx.c
+++ b/drivers/spi/spi_mpc8xxx.c
@@ -286,36 +286,12 @@ static void mpc8xxx_spi_chipselect(struct spi_device *spi, int value)
         }
 }
 
-static
-int mpc8xxx_spi_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
+static int
+mspi_apply_cpu_mode_quirks(struct spi_mpc8xxx_cs *cs,
+                           struct spi_device *spi,
+                           struct mpc8xxx_spi *mpc8xxx_spi,
+                           int bits_per_word)
 {
-        struct mpc8xxx_spi *mpc8xxx_spi;
-        u8 bits_per_word, pm;
-        u32 hz;
-        struct spi_mpc8xxx_cs   *cs = spi->controller_state;
-
-        mpc8xxx_spi = spi_master_get_devdata(spi->master);
-
-        if (t) {
-                bits_per_word = t->bits_per_word;
-                hz = t->speed_hz;
-        } else {
-                bits_per_word = 0;
-                hz = 0;
-        }
-
-        /* spi_transfer level calls that work per-word */
-        if (!bits_per_word)
-                bits_per_word = spi->bits_per_word;
-
-        /* Make sure its a bit width we support [4..16, 32] */
-        if ((bits_per_word < 4)
-            || ((bits_per_word > 16) && (bits_per_word != 32)))
-                return -EINVAL;
-
-        if (!hz)
-                hz = spi->max_speed_hz;
-
         cs->rx_shift = 0;
         cs->tx_shift = 0;
         if (bits_per_word <= 8) {
@@ -339,19 +315,82 @@ int mpc8xxx_spi_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
                 return -EINVAL;
 
         if (mpc8xxx_spi->flags & SPI_QE_CPU_MODE &&
-                        spi->mode & SPI_LSB_FIRST) {
+            spi->mode & SPI_LSB_FIRST) {
                 cs->tx_shift = 0;
                 if (bits_per_word <= 8)
                         cs->rx_shift = 8;
                 else
                         cs->rx_shift = 0;
         }
-
         mpc8xxx_spi->rx_shift = cs->rx_shift;
         mpc8xxx_spi->tx_shift = cs->tx_shift;
         mpc8xxx_spi->get_rx = cs->get_rx;
         mpc8xxx_spi->get_tx = cs->get_tx;
 
+        return bits_per_word;
+}
+
+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
+         * 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 8; /* pretend its 8 bits */
+        return bits_per_word;
+}
+
+static
+int mpc8xxx_spi_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
+{
+        struct mpc8xxx_spi *mpc8xxx_spi;
+        int bits_per_word;
+        u8 pm;
+        u32 hz;
+        struct spi_mpc8xxx_cs   *cs = spi->controller_state;
+
+        mpc8xxx_spi = spi_master_get_devdata(spi->master);
+
+        if (t) {
+                bits_per_word = t->bits_per_word;
+                hz = t->speed_hz;
+        } else {
+                bits_per_word = 0;
+                hz = 0;
+        }
+
+        /* spi_transfer level calls that work per-word */
+        if (!bits_per_word)
+                bits_per_word = spi->bits_per_word;
+
+        /* Make sure its a bit width we support [4..16, 32] */
+        if ((bits_per_word < 4)
+            || ((bits_per_word > 16) && (bits_per_word != 32)))
+                return -EINVAL;
+
+        if (!hz)
+                hz = spi->max_speed_hz;
+
+        if (!(mpc8xxx_spi->flags & SPI_CPM_MODE))
+                bits_per_word = mspi_apply_cpu_mode_quirks(cs, spi,
+                                                           mpc8xxx_spi,
+                                                           bits_per_word);
+        else if (mpc8xxx_spi->flags & SPI_QE)
+                bits_per_word = mspi_apply_qe_mode_quirks(cs, spi,
+                                                          bits_per_word);
+
+        if (bits_per_word < 0)
+                return bits_per_word;
+
         if (bits_per_word == 32)
                 bits_per_word = 0;
         else