From: Ernst Schwab <[email protected]> Added SPI bus locking functions. If the bus is locked, the SPI queue is searched for SPI transmit messages for the chipselect for which the bus is locked; no other messages will be transmitted, until the bus is unlocked again. Algorithm borrowed from the blackfin driver spi_bfin5xx.c.
Signed-off-by: Ernst Schwab <[email protected]> --- diff -upr a/drivers/spi/spi_mpc8xxx.c b/drivers/spi/spi_mpc8xxx.c --- a/drivers/spi/spi_mpc8xxx.c +++ b/drivers/spi/spi_mpc8xxx.c @@ -124,6 +124,9 @@ struct spi_pram { #define SPI_PRAM_SIZE 0x100 #define SPI_MRBLR ((unsigned int)PAGE_SIZE) +/* value for 'locked' variable to indicate that the bus is unlocked */ +#define SPIBUS_UNLOCKED 0xFF + /* SPI Controller driver's private data. */ struct mpc8xxx_spi { struct device *dev; @@ -171,6 +174,8 @@ struct mpc8xxx_spi { spinlock_t lock; struct completion done; + + u8 locked; /* chipselect number if bus is locked */ }; static void *mpc8xxx_dummy_rx; @@ -605,11 +610,39 @@ static void mpc8xxx_spi_work(struct work { struct mpc8xxx_spi *mpc8xxx_spi = container_of(work, struct mpc8xxx_spi, work); + u8 locked_cs; + u8 next_cs; spin_lock_irq(&mpc8xxx_spi->lock); while (!list_empty(&mpc8xxx_spi->queue)) { struct spi_message *m = container_of(mpc8xxx_spi->queue.next, struct spi_message, queue); + struct spi_message *msg = NULL; + + if (mpc8xxx_spi->locked != SPIBUS_UNLOCKED) { + locked_cs = mpc8xxx_spi->locked; + next_cs = m->spi->chip_select; + + if (next_cs != locked_cs) { + list_for_each_entry(msg, &mpc8xxx_spi->queue, + queue) { + next_cs = msg->spi->chip_select; + if (next_cs == locked_cs) { + m = msg; + break; + } + } + + /* + * Do nothing even if there are messages + * for other devices + */ + if (next_cs != locked_cs) { + spin_unlock_irq(&mpc8xxx_spi->lock); + return; + } + } + } list_del_init(&m->queue); spin_unlock_irq(&mpc8xxx_spi->lock); @@ -736,6 +769,50 @@ static irqreturn_t mpc8xxx_spi_irq(s32 i return ret; } +/* + * lock the spi bus for exclusive access + */ +static int mpc8xxx_spi_lock_bus(struct spi_device *spi) +{ + struct mpc8xxx_spi *mpc8xxx_spi = spi_master_get_devdata(spi->master); + unsigned long flags; + + spin_lock_irqsave(&mpc8xxx_spi->lock, flags); + if (mpc8xxx_spi->locked != SPIBUS_UNLOCKED) { + spin_unlock_irqrestore(&mpc8xxx_spi->lock, flags); + return -ENOLCK; + } + mpc8xxx_spi->locked = spi->chip_select; + + spin_unlock_irqrestore(&mpc8xxx_spi->lock, flags); + + return 0; +} + +/* + * unlock the spi bus from exclusive access + */ +static int mpc8xxx_spi_unlock_bus(struct spi_device *spi) +{ + struct mpc8xxx_spi *mpc8xxx_spi = spi_master_get_devdata(spi->master); + unsigned long flags; + + spin_lock_irqsave(&mpc8xxx_spi->lock, flags); + + /* remove the spi bus lock */ + mpc8xxx_spi->locked = SPIBUS_UNLOCKED; + + /* + * process all deferred messages for all chipselects + * other than the locked after the bus became unlocked + */ + queue_work(mpc8xxx_spi->workqueue, &mpc8xxx_spi->work); + + spin_unlock_irqrestore(&mpc8xxx_spi->lock, flags); + + return 0; +} + static int mpc8xxx_spi_transfer(struct spi_device *spi, struct spi_message *m) { @@ -992,6 +1069,8 @@ mpc8xxx_spi_probe(struct device *dev, st master->setup = mpc8xxx_spi_setup; master->transfer = mpc8xxx_spi_transfer; master->cleanup = mpc8xxx_spi_cleanup; + master->lock_bus = mpc8xxx_spi_lock_bus; + master->unlock_bus = mpc8xxx_spi_unlock_bus; mpc8xxx_spi = spi_master_get_devdata(master); mpc8xxx_spi->dev = dev; @@ -999,6 +1078,7 @@ mpc8xxx_spi_probe(struct device *dev, st mpc8xxx_spi->get_tx = mpc8xxx_spi_tx_buf_u8; mpc8xxx_spi->flags = pdata->flags; mpc8xxx_spi->spibrg = pdata->sysclk; + mpc8xxx_spi->locked = SPIBUS_UNLOCKED; ret = mpc8xxx_spi_cpm_init(mpc8xxx_spi); if (ret) ------------------------------------------------------------------------------ SOLARIS 10 is the OS for Data Centers - provides features such as DTrace, Predictive Self Healing and Award Winning ZFS. Get Solaris 10 NOW http://p.sf.net/sfu/solaris-dev2dev _______________________________________________ spi-devel-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/spi-devel-general
