Commit defbd3b4 authored by David Brownell's avatar David Brownell Committed by Linus Torvalds
Browse files

atmel_spi: don't always deselect chip between messages 



Update chipselect handling for atmel_spi:

  * Teach it how to leave chipselect active between messages; this
    helps various drivers work better.

  * Cope with at91rm0200 errata:  nCS0 can't be managed with GPIOs.
    The MR.PCS value is now updated whenever a chipselect changes.
    (This requires SPI pinmux init for that controller to change,
    and also testing on rm9200; doesn't break at91sam9 or avr32.)

  * Fix minor glitches:  spi_setup() must leave chipselects inactive,
    as must removal of the spi_device.

Also tweak diagnostic messaging to be a bit more useful.

Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Acked-by: default avatarHaavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8da0859a

drivers/spi/atmel_spi.c

+103 −24
Original line number Diff line number Diff line
@@ -46,6 +46,7 @@ struct atmel_spi { 
	struct clk		*clk;

	struct platform_device	*pdev;

	unsigned		new_1:1;

	struct spi_device	*stay;



	u8			stopping;

	struct list_head	queue;
@@ -62,28 +63,61 @@ struct atmel_spi { 
/*

 * Earlier SPI controllers (e.g. on at91rm9200) have a design bug whereby

 * they assume that spi slave device state will not change on deselect, so

 * that automagic deselection is OK.  Not so!  Workaround uses nCSx pins

 * as GPIOs; or newer controllers have CSAAT and friends.

 * that automagic deselection is OK.  ("NPCSx rises if no data is to be

 * transmitted")  Not so!  Workaround uses nCSx pins as GPIOs; or newer

 * controllers have CSAAT and friends.

 *

 * Since the CSAAT functionality is a bit weird on newer controllers

 * as well, we use GPIO to control nCSx pins on all controllers.

 * Since the CSAAT functionality is a bit weird on newer controllers as

 * well, we use GPIO to control nCSx pins on all controllers, updating

 * MR.PCS to avoid confusing the controller.  Using GPIOs also lets us

 * support active-high chipselects despite the controller's belief that

 * only active-low devices/systems exists.

 *

 * However, at91rm9200 has a second erratum whereby nCS0 doesn't work

 * right when driven with GPIO.  ("Mode Fault does not allow more than one

 * Master on Chip Select 0.")  No workaround exists for that ... so for

 * nCS0 on that chip, we (a) don't use the GPIO, (b) can't support CS_HIGH,

 * and (c) will trigger that first erratum in some cases.

 */



static inline void cs_activate(struct spi_device *spi)

static void cs_activate(struct atmel_spi *as, struct spi_device *spi)

{

	unsigned gpio = (unsigned) spi->controller_data;

	unsigned active = spi->mode & SPI_CS_HIGH;

	u32 mr;



	mr = spi_readl(as, MR);

	mr = SPI_BFINS(PCS, ~(1 << spi->chip_select), mr);



	dev_dbg(&spi->dev, "activate %u%s, mr %08x\n",

			gpio, active ? " (high)" : "",

			mr);



	dev_dbg(&spi->dev, "activate %u%s\n", gpio, active ? " (high)" : "");

	if (!(cpu_is_at91rm9200() && spi->chip_select == 0))

		gpio_set_value(gpio, active);

	spi_writel(as, MR, mr);

}



static inline void cs_deactivate(struct spi_device *spi)

static void cs_deactivate(struct atmel_spi *as, struct spi_device *spi)

{

	unsigned gpio = (unsigned) spi->controller_data;

	unsigned active = spi->mode & SPI_CS_HIGH;

	u32 mr;



	/* only deactivate *this* device; sometimes transfers to

	 * another device may be active when this routine is called.

	 */

	mr = spi_readl(as, MR);

	if (~SPI_BFEXT(PCS, mr) & (1 << spi->chip_select)) {

		mr = SPI_BFINS(PCS, 0xf, mr);

		spi_writel(as, MR, mr);

	}



	dev_dbg(&spi->dev, "DEactivate %u%s, mr %08x\n",

			gpio, active ? " (low)" : "",

			mr);



	dev_dbg(&spi->dev, "DEactivate %u%s\n", gpio, active ? " (low)" : "");

	if (!(cpu_is_at91rm9200() && spi->chip_select == 0))

		gpio_set_value(gpio, !active);

}
@@ -140,6 +174,7 @@ static void atmel_spi_next_xfer(struct spi_master *master, 


	/* REVISIT: when xfer->delay_usecs == 0, the PDC "next transfer"

	 * mechanism might help avoid the IRQ latency between transfers

	 * (and improve the nCS0 errata handling on at91rm9200 chips)

	 *

	 * We're also waiting for ENDRX before we start the next

	 * transfer because we need to handle some difficult timing
@@ -169,17 +204,25 @@ static void atmel_spi_next_message(struct spi_master *master) 
{

	struct atmel_spi	*as = spi_master_get_devdata(master);

	struct spi_message	*msg;

	u32			mr;

	struct spi_device	*spi;



	BUG_ON(as->current_transfer);



	msg = list_entry(as->queue.next, struct spi_message, queue);

	spi = msg->spi;



	/* Select the chip */

	mr = spi_readl(as, MR);

	mr = SPI_BFINS(PCS, ~(1 << msg->spi->chip_select), mr);

	spi_writel(as, MR, mr);

	cs_activate(msg->spi);

	dev_dbg(master->cdev.dev, "start message %p for %s\n",

			msg, spi->dev.bus_id);



	/* select chip if it's not still active */

	if (as->stay) {

		if (as->stay != spi) {

			cs_deactivate(as, as->stay);

			cs_activate(as, spi);

		}

		as->stay = NULL;

	} else

		cs_activate(as, spi);



	atmel_spi_next_xfer(master, msg);

}
@@ -232,9 +275,13 @@ static void atmel_spi_dma_unmap_xfer(struct spi_master *master, 


static void

atmel_spi_msg_done(struct spi_master *master, struct atmel_spi *as,

		   struct spi_message *msg, int status)

		struct spi_message *msg, int status, int stay)

{

	cs_deactivate(msg->spi);

	if (!stay || status < 0)

		cs_deactivate(as, msg->spi);

	else

		as->stay = msg->spi;



	list_del(&msg->queue);

	msg->status = status;
@@ -324,7 +371,7 @@ atmel_spi_interrupt(int irq, void *dev_id) 
		/* Clear any overrun happening while cleaning up */

		spi_readl(as, SR);



		atmel_spi_msg_done(master, as, msg, -EIO);

		atmel_spi_msg_done(master, as, msg, -EIO, 0);

	} else if (pending & SPI_BIT(ENDRX)) {

		ret = IRQ_HANDLED;
@@ -342,12 +389,13 @@ atmel_spi_interrupt(int irq, void *dev_id) 


			if (msg->transfers.prev == &xfer->transfer_list) {

				/* report completed message */

				atmel_spi_msg_done(master, as, msg, 0);

				atmel_spi_msg_done(master, as, msg, 0,

						xfer->cs_change);

			} else {

				if (xfer->cs_change) {

					cs_deactivate(msg->spi);

					cs_deactivate(as, msg->spi);

					udelay(1);

					cs_activate(msg->spi);

					cs_activate(as, msg->spi);

				}



				/*
@@ -410,6 +458,14 @@ static int atmel_spi_setup(struct spi_device *spi) 
		return -EINVAL;

	}



	/* see notes above re chipselect */

	if (cpu_is_at91rm9200()

			&& spi->chip_select == 0

			&& (spi->mode & SPI_CS_HIGH)) {

		dev_dbg(&spi->dev, "setup: can't be active-high\n");

		return -EINVAL;

	}



	/* speed zero convention is used by some upper layers */

	bus_hz = clk_get_rate(as->clk);

	if (spi->max_speed_hz) {
@@ -446,6 +502,14 @@ static int atmel_spi_setup(struct spi_device *spi) 
			return ret;

		spi->controller_state = (void *)npcs_pin;

		gpio_direction_output(npcs_pin, !(spi->mode & SPI_CS_HIGH));

	} else {

		unsigned long		flags;



		spin_lock_irqsave(&as->lock, flags);

		if (as->stay == spi)

			as->stay = NULL;

		cs_deactivate(as, spi);

		spin_unlock_irqrestore(&as->lock, flags);

	}



	dev_dbg(&spi->dev,
@@ -502,6 +566,7 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg) 
		}

	}



#ifdef VERBOSE

	list_for_each_entry(xfer, &msg->transfers, transfer_list) {

		dev_dbg(controller,

			"  xfer %p: len %u tx %p/%08x rx %p/%08x\n",
@@ -509,6 +574,7 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg) 
			xfer->tx_buf, xfer->tx_dma,

			xfer->rx_buf, xfer->rx_dma);

	}

#endif



	msg->status = -EINPROGRESS;

	msg->actual_length = 0;
@@ -524,8 +590,21 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg) 


static void atmel_spi_cleanup(struct spi_device *spi)

{

	if (spi->controller_state)

		gpio_free((unsigned int)spi->controller_data);

	struct atmel_spi	*as = spi_master_get_devdata(spi->master);

	unsigned		gpio = (unsigned) spi->controller_data;

	unsigned long		flags;



	if (!spi->controller_state)

		return;



	spin_lock_irqsave(&as->lock, flags);

	if (as->stay == spi) {

		as->stay = NULL;

		cs_deactivate(as, spi);

	}

	spin_unlock_irqrestore(&as->lock, flags);



	gpio_free(gpio);

}



/*-------------------------------------------------------------------------*/

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