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authorGeorge Shore <george@georgeshore.com>2010-01-21 14:40:52 +0300
committerGrant Likely <grant.likely@secretlab.ca>2010-01-21 17:25:32 +0300
commit052dc7c45d8f685fb3720a08331ba3e91e87937e (patch)
treeb874258f108a2ac2d8dbec12a137562d4ea4b402 /drivers/spi
parentf4aec798ae5a837a1f062e295f9a5f1b00962589 (diff)
downloadlinux-052dc7c45d8f685fb3720a08331ba3e91e87937e.tar.xz
spi/dw_spi: conditional transfer mode changes
This allows the switching between transfer modes between 'transmit only', 'receive only' and 'transmit and receive' modes. Due to the design of the SPI block, changing transfer modes requires that the block be disabled; in doing so the chipselect line is inherently deasserted and (usually) the attached device discards its state. Consequentially, switching modes requires that a platform-specific chipselect function has been defined so that the chipselect is not dropped during the change. Signed-off-by: George Shore <george@georgeshore.com> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Diffstat (limited to 'drivers/spi')
-rw-r--r--drivers/spi/dw_spi.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/drivers/spi/dw_spi.c b/drivers/spi/dw_spi.c
index 3853df5db052..e434320fded8 100644
--- a/drivers/spi/dw_spi.c
+++ b/drivers/spi/dw_spi.c
@@ -537,6 +537,22 @@ static void pump_transfers(unsigned long data)
}
message->state = RUNNING_STATE;
+ /*
+ * Adjust transfer mode if necessary. Requires platform dependent
+ * chipselect mechanism.
+ */
+ if (dws->cs_control) {
+ if (dws->rx && dws->tx)
+ chip->tmode = 0x00;
+ else if (dws->rx)
+ chip->tmode = 0x02;
+ else
+ chip->tmode = 0x01;
+
+ cr0 &= ~(0x3 << SPI_MODE_OFFSET);
+ cr0 |= (chip->tmode << SPI_TMOD_OFFSET);
+ }
+
/* Check if current transfer is a DMA transaction */
dws->dma_mapped = map_dma_buffers(dws);