spi: spi-ti-qspi: Fix FLEN and WLEN settings if bits_per_word is overridden

commit ea1b60fb upstream.

Each transfer can specify 8, 16 or 32 bits per word independently of
the default for the device being addressed.  However, currently we
calculate the number of words in the frame assuming that the word size
is the device default.

If multiple transfers in the same message have differing
bits_per_word, we bitwise-or the different values in the WLEN register
field.

Fix both of these.  Also rename 'frame_length' to 'frame_len_words' to
make clear that it's not a byte count like spi_message::frame_length.
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Mark Brown <broonie@kernel.org>
[bwh: Backported to 3.16:
 - QSPI_WLEN_MAX_BITS is not defined so use the literal value 128
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/spi/spi-ti-qspi.c

@@ -91,6 +91,7 @@ struct ti_qspi {
 /* Command */
 #define QSPI_EN_CS(n)			(n << 28)
 #define QSPI_WLEN(n)			((n - 1) << 19)
+#define QSPI_WLEN_MASK			QSPI_WLEN(128)
 #define QSPI_3_PIN			(1 << 18)
 #define QSPI_RD_SNGL			(1 << 16)
 #define QSPI_WR_SNGL			(2 << 16)
@@ -322,7 +323,7 @@ static int ti_qspi_start_transfer_one(struct spi_master *master,
 	struct spi_device *spi = m->spi;
 	struct spi_transfer *t;
 	int status = 0, ret;
-	int frame_length;
+	unsigned int frame_len_words;
 
 	/* setup device control reg */
 	qspi->dc = 0;
@@ -334,14 +335,15 @@ static int ti_qspi_start_transfer_one(struct spi_master *master,
 	if (spi->mode & SPI_CS_HIGH)
 		qspi->dc |= QSPI_CSPOL(spi->chip_select);
 
-	frame_length = (m->frame_length << 3) / spi->bits_per_word;
-
-	frame_length = clamp(frame_length, 0, QSPI_FRAME);
+	frame_len_words = 0;
+	list_for_each_entry(t, &m->transfers, transfer_list)
+		frame_len_words += t->len / (t->bits_per_word >> 3);
+	frame_len_words = min_t(unsigned int, frame_len_words, QSPI_FRAME);
 
 	/* setup command reg */
 	qspi->cmd = 0;
 	qspi->cmd |= QSPI_EN_CS(spi->chip_select);
-	qspi->cmd |= QSPI_FLEN(frame_length);
+	qspi->cmd |= QSPI_FLEN(frame_len_words);
 	qspi->cmd |= QSPI_WC_CMD_INT_EN;
 
 	ti_qspi_write(qspi, QSPI_WC_INT_EN, QSPI_INTR_ENABLE_SET_REG);
@@ -350,7 +352,8 @@ static int ti_qspi_start_transfer_one(struct spi_master *master,
 	mutex_lock(&qspi->list_lock);
 
 	list_for_each_entry(t, &m->transfers, transfer_list) {
-		qspi->cmd |= QSPI_WLEN(t->bits_per_word);
+		qspi->cmd = ((qspi->cmd & ~QSPI_WLEN_MASK) |
+			     QSPI_WLEN(t->bits_per_word));
 
 		ret = qspi_transfer_msg(qspi, t);
 		if (ret) {