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Merge pull request #12393 from benpicco/sam0-spi_reconfig

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sam0/spi: Don't re-configure SPI device when not needed
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Dylan Laduranty 2019-11-12 20:51:53 +01:00 committed by GitHub
commit 6ec6aaf4b0
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1 changed files with 24 additions and 13 deletions
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37
cpu/sam0_common/periph/spi.c
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@ -104,29 +104,40 @@ void spi_init_pins(spi_t bus)
int spi_acquire(spi_t bus, spi_cs_t cs, spi_mode_t mode, spi_clk_t clk)
{
(void) cs;
/* get exclusive access to the device */
mutex_lock(&locks[bus]);
/* power on the device */
poweron(bus);
/* disable the device */
dev(bus)->CTRLA.reg &= ~(SERCOM_SPI_CTRLA_ENABLE);
while (dev(bus)->SYNCBUSY.reg & SERCOM_SPI_SYNCBUSY_ENABLE) {}
/* configure bus clock, in synchronous mode its calculated from
* BAUD.reg = (f_ref / (2 * f_bus) - 1)
* with f_ref := CLOCK_CORECLOCK as defined by the board */
dev(bus)->BAUD.reg = (uint8_t)(((uint32_t)CLOCK_CORECLOCK) / (2 * clk) - 1);
const uint8_t baud = (((uint32_t)CLOCK_CORECLOCK) / (2 * clk) - 1);
/* configure device to be master and set mode and pads,
*
* NOTE: we could configure the pads already during spi_init, but for
* efficiency reason we do that here, so we can do all in one single write
* to the CTRLA register */
dev(bus)->CTRLA.reg = (SERCOM_SPI_CTRLA_MODE(0x3) | /* 0x3 -> master */
SERCOM_SPI_CTRLA_DOPO(spi_config[bus].mosi_pad) |
SERCOM_SPI_CTRLA_DIPO(spi_config[bus].miso_pad) |
(mode << SERCOM_SPI_CTRLA_CPHA_Pos));
const uint32_t ctrla = SERCOM_SPI_CTRLA_MODE(0x3) /* 0x3 -> master */
| SERCOM_SPI_CTRLA_DOPO(spi_config[bus].mosi_pad)
| SERCOM_SPI_CTRLA_DIPO(spi_config[bus].miso_pad)
| (mode << SERCOM_SPI_CTRLA_CPHA_Pos);
/* get exclusive access to the device */
mutex_lock(&locks[bus]);
/* power on the device */
poweron(bus);
/* configuration did not change */
if (dev(bus)->BAUD.reg == baud && dev(bus)->CTRLA.reg == ctrla) {
return SPI_OK;
}
/* disable the device */
dev(bus)->CTRLA.reg &= ~(SERCOM_SPI_CTRLA_ENABLE);
while (dev(bus)->SYNCBUSY.reg & SERCOM_SPI_SYNCBUSY_ENABLE) {}
dev(bus)->BAUD.reg = baud;
dev(bus)->CTRLA.reg = ctrla;
/* also no synchronization needed here, as CTRLA is write-synchronized */
/* finally enable the device */