drivers/spi/spi-lp8841-rtc.c

Source file repositories/reference/linux-study-clean/drivers/spi/spi-lp8841-rtc.c

File Facts

System
Linux kernel
Corpus path
drivers/spi/spi-lp8841-rtc.c
Extension
.c
Size
5339 bytes
Lines
236
Domain
Driver Families
Bucket
drivers/spi
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct spi_lp8841_rtc {
	void		*iomem;
	unsigned long	state;
};

static inline void
setsck(struct spi_lp8841_rtc *data, int is_on)
{
	if (is_on)
		data->state |= SPI_LP8841_RTC_CLK;
	else
		data->state &= ~SPI_LP8841_RTC_CLK;
	writeb(data->state, data->iomem);
}

static inline void
setmosi(struct spi_lp8841_rtc *data, int is_on)
{
	if (is_on)
		data->state |= SPI_LP8841_RTC_MOSI;
	else
		data->state &= ~SPI_LP8841_RTC_MOSI;
	writeb(data->state, data->iomem);
}

static inline int
getmiso(struct spi_lp8841_rtc *data)
{
	return ioread8(data->iomem) & SPI_LP8841_RTC_MISO;
}

static inline u32
bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data,
		unsigned usecs, unsigned cpol, unsigned flags,
		u32 word, u8 bits)
{
	/* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */

	u32 shift = 32 - bits;
	/* clock starts at inactive polarity */
	for (; likely(bits); bits--) {

		/* setup LSB (to target) on leading edge */
		if ((flags & SPI_CONTROLLER_NO_TX) == 0)
			setmosi(data, (word & 1));

		usleep_range(usecs, usecs + 1);	/* T(setup) */

		/* sample LSB (from target) on trailing edge */
		word >>= 1;
		if ((flags & SPI_CONTROLLER_NO_RX) == 0)
			word |= (getmiso(data) << 31);

		setsck(data, !cpol);
		usleep_range(usecs, usecs + 1);

		setsck(data, cpol);
	}

	word >>= shift;
	return word;
}

static int
spi_lp8841_rtc_transfer_one(struct spi_controller *host,
			    struct spi_device *spi,
			    struct spi_transfer *t)
{
	struct spi_lp8841_rtc	*data = spi_controller_get_devdata(host);
	unsigned		count = t->len;
	const u8		*tx = t->tx_buf;
	u8			*rx = t->rx_buf;
	u8			word = 0;
	int			ret = 0;

	if (tx) {
		data->state &= ~SPI_LP8841_RTC_nWE;
		writeb(data->state, data->iomem);
		while (likely(count > 0)) {
			word = *tx++;
			bitbang_txrx_be_cpha0_lsb(data, 1, 0,
					SPI_CONTROLLER_NO_RX, word, 8);
			count--;
		}
	} else if (rx) {
		data->state |= SPI_LP8841_RTC_nWE;
		writeb(data->state, data->iomem);
		while (likely(count > 0)) {
			word = bitbang_txrx_be_cpha0_lsb(data, 1, 0,
					SPI_CONTROLLER_NO_TX, word, 8);

Annotation

Implementation Notes