[PATCH v2 1/2] spi: dw: fix multiple slaves with different baudrates

[Matthias Seidel <kernel@xxxxxxxxxxx>]

Add current master clock to dws struct and compare it against the
requestedtransfer speed. Update clock divider only if necessary.

Signed-off-by: Matthias Seidel <kernel@xxxxxxxxxxx>
---
v2 First time for me, Thunderbird messed up the tabs, sorry.
---
The current implementation stores the transfer speed in the chip struct.
If there are multiple slaves which need different clock speeds, the
clk_div only gets updated the first time for each slave as speed_hz is 0.
After that the comparison always shows the transfer-speed to be
equal to the chipspeed and the divider is not updated.
---
 drivers/spi/spi-dw.c | 15 +++++++--------
 drivers/spi/spi-dw.h |  1 +
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c
index c09bb74..c85e4b3 100644
--- a/drivers/spi/spi-dw.c
+++ b/drivers/spi/spi-dw.c
@@ -283,7 +283,6 @@ static int dw_spi_transfer_one(struct spi_master *master,
 	struct chip_data *chip = spi_get_ctldata(spi);
 	u8 imask = 0;
 	u16 txlevel = 0;
-	u16 clk_div;
 	u32 cr0;
 	int ret;
 
@@ -298,13 +297,13 @@ static int dw_spi_transfer_one(struct spi_master *master,
 	spi_enable_chip(dws, 0);
 
 	/* Handle per transfer options for bpw and speed */
-	if (transfer->speed_hz != chip->speed_hz) {
-		/* clk_div doesn't support odd number */
-		clk_div = (dws->max_freq / transfer->speed_hz + 1) & 0xfffe;
-
-		chip->speed_hz = transfer->speed_hz;
-		chip->clk_div = clk_div;
-
+	if (transfer->speed_hz != dws->current_freq) {
+		if (transfer->speed_hz != chip->speed_hz) {
+			/* clk_div doesn't support odd number */
+			chip->clk_div = (dws->max_freq / transfer->speed_hz + 1) & 0xfffe;
+			chip->speed_hz = transfer->speed_hz;
+		}
+		dws->current_freq = transfer->speed_hz;
 		spi_set_clk(dws, chip->clk_div);
 	}
 	if (transfer->bits_per_word == 8) {
diff --git a/drivers/spi/spi-dw.h b/drivers/spi/spi-dw.h
index 61bc3cb..c21ca02 100644
--- a/drivers/spi/spi-dw.h
+++ b/drivers/spi/spi-dw.h
@@ -123,6 +123,7 @@ struct dw_spi {
 	u8			n_bytes;	/* current is a 1/2 bytes op */
 	u32			dma_width;
 	irqreturn_t		(*transfer_handler)(struct dw_spi *dws);
+	u32			current_freq;	/* frequency in hz */
 
 	/* DMA info */
 	int			dma_inited;
-- 
2.7.4

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