From: Imre Deak <[email protected]>
Some protocols (like one for some bitmap displays) require different clock
speed or word size settings for each transfer in an SPI message. This adds
those parameters to struct spi_transfer. They are to be used when they are
nonzero; otherwise the defaults from spi_device are to be used.
The patch also adds a setup_transfer callback to spi_bitbang, uses it for
messages that use those overrides, and implements it so that the pure
bitbanging code can help resolve any questions about how it should work.
Signed-off-by: Imre Deak <[email protected]>
Signed-off-by: David Brownell <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/spi/spi_bitbang.c | 77 ++++++++++++++++++++++++++++++++-------
include/linux/spi/spi.h | 8 ++++
include/linux/spi/spi_bitbang.h | 6 +++
3 files changed, 77 insertions(+), 14 deletions(-)
4cff33f94fefcce1b3c01a9d1da6bb85fe3cbdfa
diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c
index f037e55..0525c99 100644
--- a/drivers/spi/spi_bitbang.c
+++ b/drivers/spi/spi_bitbang.c
@@ -138,6 +138,43 @@ static unsigned bitbang_txrx_32(
return t->len - count;
}
+static int
+bitbang_transfer_setup(struct spi_device *spi, struct spi_transfer *t)
+{
+ struct spi_bitbang_cs *cs = spi->controller_state;
+ u8 bits_per_word;
+ u32 hz;
+
+ if (t) {
+ bits_per_word = t->bits_per_word;
+ hz = t->speed_hz;
+ } else {
+ bits_per_word = 0;
+ hz = 0;
+ }
+
+ /* spi_transfer level calls that work per-word */
+ if (!bits_per_word)
+ bits_per_word = spi->bits_per_word;
+ if (bits_per_word <= 8)
+ cs->txrx_bufs = bitbang_txrx_8;
+ else if (bits_per_word <= 16)
+ cs->txrx_bufs = bitbang_txrx_16;
+ else if (bits_per_word <= 32)
+ cs->txrx_bufs = bitbang_txrx_32;
+ else
+ return -EINVAL;
+
+ /* nsecs = (clock period)/2 */
+ if (!hz)
+ hz = spi->max_speed_hz;
+ cs->nsecs = (1000000000/2) / hz;
+ if (cs->nsecs > MAX_UDELAY_MS * 1000)
+ return -EINVAL;
+
+ return 0;
+}
+
/**
* spi_bitbang_setup - default setup for per-word I/O loops
*/
@@ -145,6 +182,7 @@ int spi_bitbang_setup(struct spi_device
{
struct spi_bitbang_cs *cs = spi->controller_state;
struct spi_bitbang *bitbang;
+ int retval;
if (!spi->max_speed_hz)
return -EINVAL;
@@ -160,25 +198,14 @@ int spi_bitbang_setup(struct spi_device
if (!spi->bits_per_word)
spi->bits_per_word = 8;
- /* spi_transfer level calls that work per-word */
- if (spi->bits_per_word <= 8)
- cs->txrx_bufs = bitbang_txrx_8;
- else if (spi->bits_per_word <= 16)
- cs->txrx_bufs = bitbang_txrx_16;
- else if (spi->bits_per_word <= 32)
- cs->txrx_bufs = bitbang_txrx_32;
- else
- return -EINVAL;
-
/* per-word shift register access, in hardware or bitbanging */
cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
if (!cs->txrx_word)
return -EINVAL;
- /* nsecs = (clock period)/2 */
- cs->nsecs = (1000000000/2) / (spi->max_speed_hz);
- if (cs->nsecs > MAX_UDELAY_MS * 1000)
- return -EINVAL;
+ retval = bitbang_transfer_setup(spi, NULL);
+ if (retval < 0)
+ return retval;
dev_dbg(&spi->dev, "%s, mode %d, %u bits/w, %u nsec\n",
__FUNCTION__, spi->mode & (SPI_CPOL | SPI_CPHA),
@@ -246,6 +273,8 @@ static void bitbang_work(void *_bitbang)
unsigned tmp;
unsigned cs_change;
int status;
+ int (*setup_transfer)(struct spi_device *,
+ struct spi_transfer *);
m = container_of(bitbang->queue.next, struct spi_message,
queue);
@@ -262,6 +291,7 @@ static void bitbang_work(void *_bitbang)
tmp = 0;
cs_change = 1;
status = 0;
+ setup_transfer = NULL;
list_for_each_entry (t, &m->transfers, transfer_list) {
if (bitbang->shutdown) {
@@ -269,6 +299,20 @@ static void bitbang_work(void *_bitbang)
break;
}
+ /* override or restore speed and wordsize */
+ if (t->speed_hz || t->bits_per_word) {
+ setup_transfer = bitbang->setup_transfer;
+ if (!setup_transfer) {
+ status = -ENOPROTOOPT;
+ break;
+ }
+ }
+ if (setup_transfer) {
+ status = setup_transfer(spi, t);
+ if (status < 0)
+ break;
+ }
+
/* set up default clock polarity, and activate chip;
* this implicitly updates clock and spi modes as
* previously recorded for this device via setup().
@@ -325,6 +369,10 @@ static void bitbang_work(void *_bitbang)
m->status = status;
m->complete(m->context);
+ /* restore speed and wordsize */
+ if (setup_transfer)
+ setup_transfer(spi, NULL);
+
/* normally deactivate chipselect ... unless no error and
* cs_change has hinted that the next message will probably
* be for this chip too.
@@ -406,6 +454,7 @@ int spi_bitbang_start(struct spi_bitbang
bitbang->use_dma = 0;
bitbang->txrx_bufs = spi_bitbang_bufs;
if (!bitbang->master->setup) {
+ bitbang->setup_transfer = bitbang_transfer_setup;
bitbang->master->setup = spi_bitbang_setup;
bitbang->master->cleanup = spi_bitbang_cleanup;
}
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index b05f146..caa4665 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -31,6 +31,7 @@ extern struct bus_type spi_bus_type;
* @master: SPI controller used with the device.
* @max_speed_hz: Maximum clock rate to be used with this chip
* (on this board); may be changed by the device's driver.
+ * The spi_transfer.speed_hz can override this for each transfer.
* @chip-select: Chipselect, distinguishing chips handled by "master".
* @mode: The spi mode defines how data is clocked out and in.
* This may be changed by the device's driver.
@@ -38,6 +39,7 @@ extern struct bus_type spi_bus_type;
* like eight or 12 bits are common. In-memory wordsizes are
* powers of two bytes (e.g. 20 bit samples use 32 bits).
* This may be changed by the device's driver.
+ * The spi_transfer.bits_per_word can override this for each transfer.
* @irq: Negative, or the number passed to request_irq() to receive
* interrupts from this device.
* @controller_state: Controller's runtime state
@@ -268,6 +270,10 @@ extern struct spi_master *spi_busnum_to_
* @tx_dma: DMA address of tx_buf, if spi_message.is_dma_mapped
* @rx_dma: DMA address of rx_buf, if spi_message.is_dma_mapped
* @len: size of rx and tx buffers (in bytes)
+ * @speed_hz: Select a speed other then the device default for this
+ * transfer. If 0 the default (from spi_device) is used.
+ * @bits_per_word: select a bits_per_word other then the device default
+ * for this transfer. If 0 the default (from spi_device) is used.
* @cs_change: affects chipselect after this transfer completes
* @delay_usecs: microseconds to delay after this transfer before
* (optionally) changing the chipselect status, then starting
@@ -322,7 +328,9 @@ struct spi_transfer {
dma_addr_t rx_dma;
unsigned cs_change:1;
+ u8 bits_per_word;
u16 delay_usecs;
+ u32 speed_hz;
struct list_head transfer_list;
};
diff --git a/include/linux/spi/spi_bitbang.h b/include/linux/spi/spi_bitbang.h
index c961fe9..c954557 100644
--- a/include/linux/spi/spi_bitbang.h
+++ b/include/linux/spi/spi_bitbang.h
@@ -30,6 +30,12 @@ struct spi_bitbang {
struct spi_master *master;
+ /* setup_transfer() changes clock and/or wordsize to match settings
+ * for this transfer; zeroes restore defaults from spi_device.
+ */
+ int (*setup_transfer)(struct spi_device *spi,
+ struct spi_transfer *t);
+
void (*chipselect)(struct spi_device *spi, int is_on);
#define BITBANG_CS_ACTIVE 1 /* normally nCS, active low */
#define BITBANG_CS_INACTIVE 0
--
1.3.2
-
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