Unverified Commit 25093bde authored by Alexandru Ardelean's avatar Alexandru Ardelean Committed by Mark Brown
Browse files

spi: implement SW control for CS times 



This change implements CS control for setup, hold & inactive delays.

The `cs_setup` delay is completely new, and can help with cases where
asserting the CS, also brings the device out of power-sleep, where there
needs to be a longer (than usual), before transferring data.

The `cs_hold` time can overlap with the `delay` (or `delay_usecs`) from an
SPI transfer. The main difference is that `cs_hold` implies that CS will be
de-asserted.

The `cs_inactive` delay does not have a clear use-case yet. It has been
implemented mostly because the `spi_set_cs_timing()` function implements
it. To some degree, this could overlap or replace `cs_change_delay`, but
this will require more consideration/investigation in the future.

All these delays have been added to the `spi_controller` struct, as they
would typically be configured by calling `spi_set_cs_timing()` after an
`spi_setup()` call.

Software-mode for CS control, implies that the `set_cs_timing()` hook has
not been provided for the `spi_controller` object.

Signed-off-by: default avatarAlexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20190926105147.7839-16-alexandru.ardelean@analog.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 81059366

drivers/spi/spi.c

+44 −1
Original line number Diff line number Diff line
@@ -775,6 +775,15 @@ int spi_register_board_info(struct spi_board_info const *info, unsigned n) 


static void spi_set_cs(struct spi_device *spi, bool enable)

{

	bool enable1 = enable;



	if (!spi->controller->set_cs_timing) {

		if (enable1)

			spi_delay_exec(&spi->controller->cs_setup, NULL);

		else

			spi_delay_exec(&spi->controller->cs_hold, NULL);

	}



	if (spi->mode & SPI_CS_HIGH)

		enable = !enable;
@@ -800,6 +809,11 @@ static void spi_set_cs(struct spi_device *spi, bool enable) 
	} else if (spi->controller->set_cs) {

		spi->controller->set_cs(spi, !enable);

	}



	if (!spi->controller->set_cs_timing) {

		if (!enable1)

			spi_delay_exec(&spi->controller->cs_inactive, NULL);

	}

}



#ifdef CONFIG_HAS_DMA
@@ -3278,11 +3292,40 @@ EXPORT_SYMBOL_GPL(spi_setup); 
int spi_set_cs_timing(struct spi_device *spi, struct spi_delay *setup,

		      struct spi_delay *hold, struct spi_delay *inactive)

{

	size_t len;



	if (spi->controller->set_cs_timing)

		return spi->controller->set_cs_timing(spi, setup, hold,

						      inactive);



	if ((setup && setup->unit == SPI_DELAY_UNIT_SCK) ||

	    (hold && hold->unit == SPI_DELAY_UNIT_SCK) ||

	    (inactive && inactive->unit == SPI_DELAY_UNIT_SCK)) {

		dev_err(&spi->dev,

			"Clock-cycle delays for CS not supported in SW mode\n");

		return -ENOTSUPP;

	}



	len = sizeof(struct spi_delay);



	/* copy delays to controller */

	if (setup)

		memcpy(&spi->controller->cs_setup, setup, len);

	else

		memset(&spi->controller->cs_setup, 0, len);



	if (hold)

		memcpy(&spi->controller->cs_hold, hold, len);

	else

		memset(&spi->controller->cs_hold, 0, len);



	if (inactive)

		memcpy(&spi->controller->cs_inactive, inactive, len);

	else

		memset(&spi->controller->cs_inactive, 0, len);



	return 0;

}

EXPORT_SYMBOL_GPL(spi_set_cs_timing);



static int _spi_xfer_word_delay_update(struct spi_transfer *xfer,

include/linux/spi/spi.h

+5 −0
Original line number Diff line number Diff line
@@ -609,6 +609,11 @@ struct spi_controller { 
	/* Optimized handlers for SPI memory-like operations. */

	const struct spi_controller_mem_ops *mem_ops;



	/* CS delays */

	struct spi_delay	cs_setup;

	struct spi_delay	cs_hold;

	struct spi_delay	cs_inactive;



	/* gpio chip select */

	int			*cs_gpios;

	struct gpio_desc	**cs_gpiods;

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