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cc2538: spi: Add support for dynamic clock frequency

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This changes makes it possible to change the SPI clock frequency at
runtime.

Signed-off-by: Benoît Thébaudeau <benoit@wsystem.com>
This commit is contained in:
Benoît Thébaudeau 2016-11-17 17:53:34 +01:00 committed by Benoît Thébaudeau
parent c76b8235f4
commit 8b57670121
2 changed files with 46 additions and 1 deletions
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39
cpu/cc2538/dev/spi.c
View file

@ -40,6 +40,7 @@
#include "contiki.h"
#include "reg.h"
#include "spi-arch.h"
#include "sys/cc.h"
#include "dev/ioc.h"
#include "dev/sys-ctrl.h"
#include "dev/spi.h"
@ -155,7 +156,12 @@
#if (SPI1_CPRS_CPSDVSR & 1) == 1 || SPI1_CPRS_CPSDVSR < 2 || SPI1_CPRS_CPSDVSR > 254
#error SPI1_CPRS_CPSDVSR must be an even number between 2 and 254
#endif
/*---------------------------------------------------------------------------*/
/*
* Clock source from which the baud clock is determined for the SSI, according
* to SSI_CC.CS.
*/
#define SSI_SYS_CLOCK SYS_CTRL_SYS_CLOCK
/*---------------------------------------------------------------------------*/
typedef struct {
int8_t port;
@ -314,6 +320,37 @@ spix_set_mode(uint8_t spi,
}
/*---------------------------------------------------------------------------*/
void
spix_set_clock_freq(uint8_t spi, uint32_t freq)
{
const spi_regs_t *regs;
uint64_t div;
uint32_t scr;
if(spi >= SSI_INSTANCE_COUNT) {
return;
}
regs = &spi_regs[spi];
/* Disable the SSI peripheral to configure it */
REG(regs->base + SSI_CR1) = 0;
/* Configure the SSI serial clock rate */
if(!freq) {
scr = 255;
} else {
div = (uint64_t)regs->ssi_cprs_cpsdvsr * freq;
scr = (SSI_SYS_CLOCK + div - 1) / div;
scr = MIN(MAX(scr, 1), 256) - 1;
}
REG(regs->base + SSI_CR0) = (REG(regs->base + SSI_CR0) & ~SSI_CR0_SCR_M) |
scr << SSI_CR0_SCR_S;
/* Re-enable the SSI */
REG(regs->base + SSI_CR1) |= SSI_CR1_SSE;
}
/*---------------------------------------------------------------------------*/
void
spix_cs_init(uint8_t port, uint8_t pin)
{
GPIO_SOFTWARE_CONTROL(GPIO_PORT_TO_BASE(port),

8
cpu/cc2538/spi-arch.h
View file

@ -197,6 +197,14 @@ void spix_set_mode(uint8_t spi, uint32_t frame_format,
uint32_t clock_polarity, uint32_t clock_phase,
uint32_t data_size);
/**
* \brief Sets the SPI clock frequency of the given SSI instance.
*
* \param spi SSI instance
* \param freq Frequency (Hz)
*/
void spix_set_clock_freq(uint8_t spi, uint32_t freq);
/**
* \brief Configure a GPIO to be the chip select pin.
*