From fd5e191e7610eb7ecb5e35b2045ceb6554bea15a Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Mon, 6 Apr 2009 19:00:56 -0700 Subject: SPI: add dma_alignment field to spi_master Some SPI controllers have restrictions on DMAable buffers alignemt. Currently if the buffer supplied by protocol driver is not properly aligned, the controller silently performs transfer in PIO mode. Addition of dma_alignment field to spi_master allows protocol drivers to perform proper alignment. Signed-off-by: Mike Rapoport Cc: Bryan Wu Cc: David Brownell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/spi/spi.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/linux/spi/spi.h') diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 68bb1c501d0..2cc43fa380c 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -204,6 +204,7 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv) * SPI slaves, and are numbered from zero to num_chipselects. * each slave has a chipselect signal, but it's common that not * every chipselect is connected to a slave. + * @dma_alignment: SPI controller constraint on DMA buffers alignment. * @setup: updates the device mode and clocking records used by a * device's SPI controller; protocol code may call this. This * must fail if an unrecognized or unsupported mode is requested. @@ -239,6 +240,11 @@ struct spi_master { */ u16 num_chipselect; + /* some SPI controllers pose alignment requirements on DMAable + * buffers; let protocol drivers know about these requirements. + */ + u16 dma_alignment; + /* setup mode and clock, etc (spi driver may call many times) */ int (*setup)(struct spi_device *spi); -- cgit v1.2.3-70-g09d2 From 6e538aaf50ae782a890cbc02c27950448d8193e1 Mon Sep 17 00:00:00 2001 From: David Brownell Date: Tue, 21 Apr 2009 12:24:49 -0700 Subject: spi: documentation: emphasise spi_master.setup() semantics This is a doc-only patch which I hope will reduce the number of spi_master controller driver patches starting out with a common implementation bug. (As in: almost every spi_master driver I see starts out with its version of this bug. Sigh.) It just re-emphasizes that the setup() method may be called for one device while a transfer is active on another ... which means that most driver implementations shouldn't touch any registers. Signed-off-by: David Brownell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/spi/spi-summary | 6 ++++++ include/linux/spi/spi.h | 7 ++++++- 2 files changed, 12 insertions(+), 1 deletion(-) (limited to 'include/linux/spi/spi.h') 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 -- cgit v1.2.3-70-g09d2