[PATCH 16/20] Blackfin SPI Driver: fix bug - correct usage of struct spi_transfer.cs_change

Bryan Wu
2009-02-06T07:16:49Z

From: Yi Li <yi.li@analog.com>

According to comments in linux/spi/spi.h:

* All SPI transfers start with the relevant chipselect active. Normally
* it stays selected until after the last transfer in a message. Drivers
* can affect the chipselect signal using cs_change.
*
* (i) If the transfer isn't the last one in the message, this flag is
* used to make the chipselect briefly go inactive in the middle of the
* message. Toggling chipselect in this way may be needed to terminate
* a chip command, letting a single spi_message perform all of group of
* chip transactions together.
*
* (ii) When the transfer is the last one in the message, the chip may
* stay selected until the next transfer. On multi-device SPI busses
* with nothing blocking messages going to other devices, this is just
* a performance hint; starting a message to another device deselects
* this one. But in other cases, this can be used to ensure correctness.
* Some devices need protocol transactions to be built from a series of
* spi_message submissions, where the content of one message is determined
* by the results of previous messages and where the whole transaction
* ends when the chipselect goes intactive.

Signed-off-by: Yi Li <yi.li@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
---
drivers/spi/spi_bfin5xx.c | 17 ++++++++---------
1 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/spi/spi_bfin5xx.c b/drivers/spi/spi_bfin5xx.c
index ed6a4c1..811a305 100644
--- a/drivers/spi/spi_bfin5xx.c
+++ b/drivers/spi/spi_bfin5xx.c
@@ -540,15 +540,13 @@ static void giveback(struct driver_data *drv_data)

msg->state = NULL;

- /* disable chip select signal. And not stop spi in autobuffer mode */
- if (drv_data->tx_dma != 0xFFFF) {
- cs_deactive(drv_data, chip);
- bfin_spi_disable(drv_data);
- }
-
if (!drv_data->cs_change)
cs_deactive(drv_data, chip);

+ /* Not stop spi in autobuffer mode */
+ if (drv_data->tx_dma != 0xFFFF)
+ bfin_spi_disable(drv_data);
+
if (msg->complete)
msg->complete(msg->context);
}
@@ -757,7 +755,8 @@ static void pump_transfers(unsigned long data)

write_STAT(drv_data, BIT_STAT_CLR);
cr = (read_CTRL(drv_data) & (~BIT_CTL_TIMOD));
- cs_active(drv_data, chip);
+ if (drv_data->cs_change)
+ cs_active(drv_data, chip);

dev_dbg(&drv_data->pdev->dev,
"now pumping a transfer: width is %d, len is %d\n",
@@ -919,11 +918,11 @@ static void pump_transfers(unsigned long data)
} else {
/* Update total byte transfered */
message->actual_length += drv_data->len_in_bytes;
-
/* Move to next transfer of this msg */
message->state = next_transfer(drv_data);
+ if (drv_data->cs_change)
+ cs_deactive(drv_data, chip);
}
-
/* Schedule next transfer tasklet */
tasklet_schedule(&drv_data->pump_transfers);

--
1.5.6.3