6.10-stable review patch. If anyone has any objections, please let me know.
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From: Steve Wilkins steve.wilkins@raymarine.com
[ Upstream commit 22fd98c107c792e35db7abe45298bc3a29bf4723 ]
Setting up many of the registers for a new SPI transfer requires the SPI controller to be disabled after set_cs() has been called to assert the chip select line. However, disabling the controller results in the SCLK and MOSI output pins being tristate, which can cause clock transitions to be seen by a slave device whilst SS is active. To fix this, the CS is only set to inactive inline, whilst setting it active is deferred until all registers are set up and the any controller disables have been completed.
Fixes: 9ac8d17694b6 ("spi: add support for microchip fpga spi controllers") Signed-off-by: Steve Wilkins steve.wilkins@raymarine.com Signed-off-by: Conor Dooley conor.dooley@microchip.com Link: https://patch.msgid.link/20240715-sanitizer-recant-dd96b7a97048@wendy Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/spi/spi-microchip-core.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/drivers/spi/spi-microchip-core.c b/drivers/spi/spi-microchip-core.c index 003a2bc3cfd1b..8043a18e7c3bd 100644 --- a/drivers/spi/spi-microchip-core.c +++ b/drivers/spi/spi-microchip-core.c @@ -103,6 +103,7 @@ struct mchp_corespi { u8 *rx_buf; u32 clk_gen; /* divider for spi output clock generated by the controller */ u32 clk_mode; + u32 pending_slave_select; int irq; int tx_len; int rx_len; @@ -249,8 +250,18 @@ static void mchp_corespi_set_cs(struct spi_device *spi, bool disable) reg = mchp_corespi_read(corespi, REG_SLAVE_SELECT); reg &= ~BIT(spi_get_chipselect(spi, 0)); reg |= !disable << spi_get_chipselect(spi, 0); + corespi->pending_slave_select = reg;
- mchp_corespi_write(corespi, REG_SLAVE_SELECT, reg); + /* + * Only deassert chip select immediately. Writing to some registers + * requires the controller to be disabled, which results in the + * output pins being tristated and can cause the SCLK and MOSI lines + * to transition. Therefore asserting the chip select is deferred + * until just before writing to the TX FIFO, to ensure the device + * doesn't see any spurious clock transitions whilst CS is enabled. + */ + if (((spi->mode & SPI_CS_HIGH) == 0) == disable) + mchp_corespi_write(corespi, REG_SLAVE_SELECT, reg); }
static int mchp_corespi_setup(struct spi_device *spi) @@ -266,6 +277,7 @@ static int mchp_corespi_setup(struct spi_device *spi) if (spi->mode & SPI_CS_HIGH) { reg = mchp_corespi_read(corespi, REG_SLAVE_SELECT); reg |= BIT(spi_get_chipselect(spi, 0)); + corespi->pending_slave_select = reg; mchp_corespi_write(corespi, REG_SLAVE_SELECT, reg); } return 0; @@ -307,7 +319,8 @@ static void mchp_corespi_init(struct spi_controller *host, struct mchp_corespi * * select is relinquished to the hardware. SSELOUT is enabled too so we * can deal with active high targets. */ - mchp_corespi_write(spi, REG_SLAVE_SELECT, SSELOUT | SSEL_DIRECT); + spi->pending_slave_select = SSELOUT | SSEL_DIRECT; + mchp_corespi_write(spi, REG_SLAVE_SELECT, spi->pending_slave_select);
control = mchp_corespi_read(spi, REG_CONTROL);
@@ -476,6 +489,8 @@ static int mchp_corespi_transfer_one(struct spi_controller *host, mchp_corespi_set_xfer_size(spi, (spi->tx_len > FIFO_DEPTH) ? FIFO_DEPTH : spi->tx_len);
+ mchp_corespi_write(spi, REG_SLAVE_SELECT, spi->pending_slave_select); + while (spi->tx_len) mchp_corespi_write_fifo(spi);