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 0f5122eb282b..4a02d2508bc8 100644 --- a/Documentation/spi/spi-summary +++ b/Documentation/spi/spi-summary | |||
@@ -511,10 +511,16 @@ SPI MASTER METHODS | |||
511 | This sets up the device clock rate, SPI mode, and word sizes. | 511 | This sets up the device clock rate, SPI mode, and word sizes. |
512 | Drivers may change the defaults provided by board_info, and then | 512 | Drivers may change the defaults provided by board_info, and then |
513 | call spi_setup(spi) to invoke this routine. It may sleep. | 513 | call spi_setup(spi) to invoke this routine. It may sleep. |
514 | |||
514 | Unless each SPI slave has its own configuration registers, don't | 515 | Unless each SPI slave has its own configuration registers, don't |
515 | change them right away ... otherwise drivers could corrupt I/O | 516 | change them right away ... otherwise drivers could corrupt I/O |
516 | that's in progress for other SPI devices. | 517 | that's in progress for other SPI devices. |
517 | 518 | ||
519 | ** BUG ALERT: for some reason the first version of | ||
520 | ** many spi_master drivers seems to get this wrong. | ||
521 | ** When you code setup(), ASSUME that the controller | ||
522 | ** is actively processing transfers for another device. | ||
523 | |||
518 | master->transfer(struct spi_device *spi, struct spi_message *message) | 524 | master->transfer(struct spi_device *spi, struct spi_message *message) |
519 | This must not sleep. Its responsibility is arrange that the | 525 | This must not sleep. Its responsibility is arrange that the |
520 | transfer happens and its complete() callback is issued. The two | 526 | 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 2cc43fa380cb..a0faa18f7b1b 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h | |||
@@ -245,7 +245,12 @@ struct spi_master { | |||
245 | */ | 245 | */ |
246 | u16 dma_alignment; | 246 | u16 dma_alignment; |
247 | 247 | ||
248 | /* setup mode and clock, etc (spi driver may call many times) */ | 248 | /* Setup mode and clock, etc (spi driver may call many times). |
249 | * | ||
250 | * IMPORTANT: this may be called when transfers to another | ||
251 | * device are active. DO NOT UPDATE SHARED REGISTERS in ways | ||
252 | * which could break those transfers. | ||
253 | */ | ||
249 | int (*setup)(struct spi_device *spi); | 254 | int (*setup)(struct spi_device *spi); |
250 | 255 | ||
251 | /* bidirectional bulk transfers | 256 | /* bidirectional bulk transfers |