diff options
| -rw-r--r-- | drivers/spi/spi-microchip-core.c | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/drivers/spi/spi-microchip-core.c b/drivers/spi/spi-microchip-core.c index c8076333d179..a78900db2397 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) @@ -269,6 +280,7 @@ 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; @@ -310,7 +322,8 @@ 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); @@ -479,6 +492,8 @@ 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); |