diff options
| -rw-r--r-- | Documentation/spi/spi-summary | 6 | ||||
| -rw-r--r-- | include/linux/spi/spi.h | 7 |
2 files changed, 12 insertions, 1 deletions
diff --git a/Documentation/spi/spi-summary b/Documentation/spi/spi-summary index 0f5122eb282..4a02d2508bc 100644 --- a/Documentation/spi/spi-summary +++ b/Documentation/spi/spi-summary @@ -511,10 +511,16 @@ SPI MASTER METHODS This sets up the device clock rate, SPI mode, and word sizes. Drivers may change the defaults provided by board_info, and then call spi_setup(spi) to invoke this routine. It may sleep. + Unless each SPI slave has its own configuration registers, don't change them right away ... otherwise drivers could corrupt I/O that's in progress for other SPI devices. + ** BUG ALERT: for some reason the first version of + ** many spi_master drivers seems to get this wrong. + ** When you code setup(), ASSUME that the controller + ** is actively processing transfers for another device. + master->transfer(struct spi_device *spi, struct spi_message *message) This must not sleep. Its responsibility is arrange that the transfer happens and its complete() callback is issued. The two diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 2cc43fa380c..a0faa18f7b1 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -245,7 +245,12 @@ struct spi_master { */ u16 dma_alignment; - /* setup mode and clock, etc (spi driver may call many times) */ + /* Setup mode and clock, etc (spi driver may call many times). + * + * IMPORTANT: this may be called when transfers to another + * device are active. DO NOT UPDATE SHARED REGISTERS in ways + * which could break those transfers. + */ int (*setup)(struct spi_device *spi); /* bidirectional bulk transfers |