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author | Yi Li <yi.li@analog.com> | 2009-04-07 02:00:49 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-04-07 15:31:06 (GMT) |
commit | b9b2a76a4391cadb6d42da2ccf5e956c459acb72 (patch) | |
tree | a4526204a924fedcaa2f1ea028ae9b2d22fb1faa /drivers/spi | |
parent | 2cf3683472f043e6748c48228df6d8a35a47ecc2 (diff) | |
download | linux-b9b2a76a4391cadb6d42da2ccf5e956c459acb72.tar.xz |
Blackfin SPI Driver: fix bug - correct usage of struct spi_transfer.cs_change
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>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/spi')
-rw-r--r-- | 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 1222925..bdad0bb 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); |