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spi: bitbang: Implement support for MOSI idle state configuration

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Some SPI peripherals may require strict MOSI line state when the controller
is not clocking out data. Implement support for MOSI idle state
configuration (low or high) by setting the data output line level on
controller setup and after transfers. Bitbang operations now call
controller specific set_mosi_idle() callback to set MOSI to its idle state.
The MOSI line is kept at its idle state if no tx buffer is provided.

Acked-by: Nuno Sa <nuno.sa@analog.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Link: https://patch.msgid.link/de61a600b56ed9cb714d5ea87afa88948e70041e.1720810545.git.marcelo.schmitt@analog.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Marcelo Schmitt 2024-07-12 16:21:03 -03:00 committed by Mark Brown
parent f58872f45c
commit 320f669309
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
2 changed files with 25 additions and 0 deletions
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24
drivers/spi/spi-bitbang.c
View File

@ -54,21 +54,28 @@ static unsigned int bitbang_txrx_8(struct spi_device *spi,
struct spi_transfer *t,
unsigned int flags)
{
struct spi_bitbang *bitbang;
unsigned int bits = t->bits_per_word;
unsigned int count = t->len;
const u8 *tx = t->tx_buf;
u8 *rx = t->rx_buf;
bitbang = spi_controller_get_devdata(spi->controller);
while (likely(count > 0)) {
u8 word = 0;
if (tx)
word = *tx++;
else
word = spi->mode & SPI_MOSI_IDLE_HIGH ? 0xFF : 0;
word = txrx_word(spi, ns, word, bits, flags);
if (rx)
*rx++ = word;
count -= 1;
}
if (bitbang->set_mosi_idle)
bitbang->set_mosi_idle(spi);
return t->len - count;
}
@ -78,21 +85,28 @@ static unsigned int bitbang_txrx_16(struct spi_device *spi,
struct spi_transfer *t,
unsigned int flags)
{
struct spi_bitbang *bitbang;
unsigned int bits = t->bits_per_word;
unsigned int count = t->len;
const u16 *tx = t->tx_buf;
u16 *rx = t->rx_buf;
bitbang = spi_controller_get_devdata(spi->controller);
while (likely(count > 1)) {
u16 word = 0;
if (tx)
word = *tx++;
else
word = spi->mode & SPI_MOSI_IDLE_HIGH ? 0xFFFF : 0;
word = txrx_word(spi, ns, word, bits, flags);
if (rx)
*rx++ = word;
count -= 2;
}
if (bitbang->set_mosi_idle)
bitbang->set_mosi_idle(spi);
return t->len - count;
}
@ -102,21 +116,28 @@ static unsigned int bitbang_txrx_32(struct spi_device *spi,
struct spi_transfer *t,
unsigned int flags)
{
struct spi_bitbang *bitbang;
unsigned int bits = t->bits_per_word;
unsigned int count = t->len;
const u32 *tx = t->tx_buf;
u32 *rx = t->rx_buf;
bitbang = spi_controller_get_devdata(spi->controller);
while (likely(count > 3)) {
u32 word = 0;
if (tx)
word = *tx++;
else
word = spi->mode & SPI_MOSI_IDLE_HIGH ? 0xFFFFFFFF : 0;
word = txrx_word(spi, ns, word, bits, flags);
if (rx)
*rx++ = word;
count -= 4;
}
if (bitbang->set_mosi_idle)
bitbang->set_mosi_idle(spi);
return t->len - count;
}
@ -192,6 +213,9 @@ int spi_bitbang_setup(struct spi_device *spi)
goto err_free;
}
if (bitbang->set_mosi_idle)
bitbang->set_mosi_idle(spi);
dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
return 0;

1
include/linux/spi/spi_bitbang.h
View File

@ -24,6 +24,7 @@ struct spi_bitbang {
#define BITBANG_CS_ACTIVE 1 /* normally nCS, active low */
#define BITBANG_CS_INACTIVE 0
void (*set_mosi_idle)(struct spi_device *spi);
/* txrx_bufs() may handle dma mapping for transfers that don't
* already have one (transfer.{tx,rx}_dma is zero), or use PIO
*/