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Commit e508cea4 authored by Heiner Kallweit's avatar Heiner Kallweit Committed by Mark Brown
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spi: fsl-espi: make better use of the RX FIFO 



So far an interrupt is triggered whenever there's at least one byte
in the RX FIFO. This results in a unnecessarily high number of
interrupts.
Change this to generate an interrupt if
- RX FIFO is half full (except if all bytes to read fit into the
  RX FIFO anyway)
- end of transfer has been reached

This way the number of interrupts can be significantly reduced.

Signed-off-by: default avatarHeiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent db1b049f

drivers/spi/spi-fsl-espi.c

+8 −3
Original line number Diff line number Diff line
@@ -55,9 +55,10 @@ 
#define CSMODE_CG(x)		((x) << 3)



#define FSL_ESPI_FIFO_SIZE	32

#define FSL_ESPI_RXTHR		15



/* Default mode/csmode for eSPI controller */

#define SPMODE_INIT_VAL (SPMODE_TXTHR(4) | SPMODE_RXTHR(3))

#define SPMODE_INIT_VAL (SPMODE_TXTHR(4) | SPMODE_RXTHR(FSL_ESPI_RXTHR))

#define CSMODE_INIT_VAL (CSMODE_POL_1 | CSMODE_BEF(0) \

		| CSMODE_AFT(0) | CSMODE_CG(1))
@@ -263,6 +264,7 @@ static void fsl_espi_setup_transfer(struct spi_device *spi, 
static int fsl_espi_bufs(struct spi_device *spi, struct spi_transfer *t)

{

	struct mpc8xxx_spi *mpc8xxx_spi = spi_master_get_devdata(spi->master);

	u32 mask;

	int ret;



	mpc8xxx_spi->rx_len = t->len;
@@ -277,8 +279,11 @@ static int fsl_espi_bufs(struct spi_device *spi, struct spi_transfer *t) 
	fsl_espi_write_reg(mpc8xxx_spi, ESPI_SPCOM,

		(SPCOM_CS(spi->chip_select) | SPCOM_TRANLEN(t->len - 1)));



	/* enable rx ints */

	fsl_espi_write_reg(mpc8xxx_spi, ESPI_SPIM, SPIM_RNE);

	/* enable interrupts */

	mask = SPIM_DON;

	if (mpc8xxx_spi->rx_len > FSL_ESPI_FIFO_SIZE)

		mask |= SPIM_RXT;

	fsl_espi_write_reg(mpc8xxx_spi, ESPI_SPIM, mask);



	/* Prevent filling the fifo from getting interrupted */

	spin_lock_irq(&mpc8xxx_spi->lock);