| Message ID | 6b6bad3844828c22de3acfb9e7fbac877a48d5a4.1646060734.git.christophe.leroy@csgroup.eu (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add support for components requiring trailing clock after transfer | expand |
On Mon, 28 Feb 2022 16:15:45 +0100, Christophe Leroy wrote: > Some components require a few clock cycles with chipselect off before > or/and after the data transfer done with CS on. > > Typically IDT 801034 QUAD PCM CODEC datasheet states "Note *: CCLK > should have one cycle before CS goes low, and two cycles after > CS goes high". > > The cycles "before" are implicitely provided by all previous activity > on the SPI bus. But the cycles "after" must be provided in order to > achieve the SPI transfer. > > In order to use that kind of component, implement a new option for > SPI slaves in order to implement trailing clock of a given number of > bits with ChipSelect off at the end of the transfer. > > Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> > --- > .../devicetree/bindings/spi/spi-peripheral-props.yaml | 5 +++++ > drivers/spi/spi.c | 7 +++++-- > include/linux/spi/spi.h | 1 + > 3 files changed, 11 insertions(+), 2 deletions(-) > Acked-by: Rob Herring <robh@kernel.org>
diff --git a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml index 5dd209206e88..2fd5a5084dbe 100644 --- a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml +++ b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml @@ -82,6 +82,11 @@ properties: description: Delay, in microseconds, after a write transfer. + spi-trailing-bits: + $ref: /schemas/types.yaml#/definitions/uint32 + description: + Number of clock cycles with chipselect OFF after transfers. + # The controller specific properties go here. allOf: - $ref: cdns,qspi-nor-peripheral-props.yaml# diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 4599b121d744..2b204fd20337 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -2159,6 +2159,9 @@ static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi, } } + if (!of_property_read_u32(nc, "spi-trailing-bits", &value)) + spi->trailing_bits = value; + if (spi_controller_is_slave(ctlr)) { if (!of_node_name_eq(nc, "slave")) { dev_err(&ctlr->dev, "%pOF is not called 'slave'\n", @@ -3538,14 +3541,14 @@ int spi_setup(struct spi_device *spi) trace_spi_setup(spi, status); - dev_dbg(&spi->dev, "setup mode %lu, %s%s%s%s%u bits/w, %u Hz max --> %d\n", + dev_dbg(&spi->dev, "setup mode %lu, %s%s%s%s%u bits/w, %u Hz max, %d trailing bits --> %d\n", spi->mode & SPI_MODE_X_MASK, (spi->mode & SPI_CS_HIGH) ? "cs_high, " : "", (spi->mode & SPI_LSB_FIRST) ? "lsb, " : "", (spi->mode & SPI_3WIRE) ? "3wire, " : "", (spi->mode & SPI_LOOP) ? "loopback, " : "", spi->bits_per_word, spi->max_speed_hz, - status); + spi->trailing_bits, status); return status; } diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 7ab3fed7b804..3f1e3d788f08 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -166,6 +166,7 @@ struct spi_device { u32 max_speed_hz; u8 chip_select; u8 bits_per_word; + u8 trailing_bits; bool rt; #define SPI_NO_TX BIT(31) /* no transmit wire */ #define SPI_NO_RX BIT(30) /* no receive wire */
Some components require a few clock cycles with chipselect off before or/and after the data transfer done with CS on. Typically IDT 801034 QUAD PCM CODEC datasheet states "Note *: CCLK should have one cycle before CS goes low, and two cycles after CS goes high". The cycles "before" are implicitely provided by all previous activity on the SPI bus. But the cycles "after" must be provided in order to achieve the SPI transfer. In order to use that kind of component, implement a new option for SPI slaves in order to implement trailing clock of a given number of bits with ChipSelect off at the end of the transfer. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> --- .../devicetree/bindings/spi/spi-peripheral-props.yaml | 5 +++++ drivers/spi/spi.c | 7 +++++-- include/linux/spi/spi.h | 1 + 3 files changed, 11 insertions(+), 2 deletions(-)