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: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/spi/atmel_spi.c b/drivers/spi/atmel_spi.c
index 01ad632..ad14405 100644 (file)
--- a/drivers/spi/atmel_spi.c
+++ b/drivers/spi/atmel_spi.c
@@ -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;
@@ -62,29 +63,62 @@ 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)" : "");
-       gpio_set_value(gpio, active);
+       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;
 
-       dev_dbg(&spi->dev, "DEactivate %u%s\n", gpio, active ? " (low)" : "");
-       gpio_set_value(gpio, !active);
+       /* 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);
+
+       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);
 }
 
 /*-------------------------------------------------------------------------*/