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authorDavid Brownell <dbrownell@users.sourceforge.net>2009-06-30 11:41:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-30 18:56:00 -0700
commit70d6027ff2bc8bab180273b77e7ab3e8a62cca51 (patch)
tree1b8e13ffd71c587dcff60933d69a9ff2edb60f0d
parentb55f627feeb9d48fdbde3835e18afbc76712e49b (diff)
downloadlinux-70d6027ff2bc8bab180273b77e7ab3e8a62cca51.tar.bz2
spi: add spi_master flag word
Add a new spi_master.flags word listing constraints relevant to that controller. Define the first constraint bit: a half duplex restriction. Include that constraint in the OMAP1 MicroWire controller driver. Have the mmc_spi host be the first customer of this flag. Its coding relies heavily on full duplex transfers, so it must fail when the underlying controller driver won't perform them. (The spi_write_then_read routine could use it too: use the temporarily-withdrawn full-duplex speedup unless this flag is set, in which case the existing code applies. Similarly, any spi_master implementing only SPI_3WIRE should set the flag.) Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--drivers/mmc/host/mmc_spi.c6
-rw-r--r--drivers/spi/omap_uwire.c2
-rw-r--r--include/linux/spi/spi.h4
3 files changed, 12 insertions, 0 deletions
diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c
index 240608cc7ae9..a461017ce5ce 100644
--- a/drivers/mmc/host/mmc_spi.c
+++ b/drivers/mmc/host/mmc_spi.c
@@ -1313,6 +1313,12 @@ static int mmc_spi_probe(struct spi_device *spi)
struct mmc_spi_host *host;
int status;
+ /* We rely on full duplex transfers, mostly to reduce
+ * per-transfer overheads (by making fewer transfers).
+ */
+ if (spi->master->flags & SPI_MASTER_HALF_DUPLEX)
+ return -EINVAL;
+
/* MMC and SD specs only seem to care that sampling is on the
* rising edge ... meaning SPI modes 0 or 3. So either SPI mode
* should be legit. We'll use mode 0 since the steady state is 0,
diff --git a/drivers/spi/omap_uwire.c b/drivers/spi/omap_uwire.c
index aa90ddb37066..8980a5640bd9 100644
--- a/drivers/spi/omap_uwire.c
+++ b/drivers/spi/omap_uwire.c
@@ -514,6 +514,8 @@ static int __init uwire_probe(struct platform_device *pdev)
/* the spi->mode bits understood by this driver: */
master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
+ master->flags = SPI_MASTER_HALF_DUPLEX;
+
master->bus_num = 2; /* "official" */
master->num_chipselect = 4;
master->setup = uwire_setup;
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 743c933ac4e7..c47c4b4da97e 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -250,6 +250,10 @@ struct spi_master {
/* spi_device.mode flags understood by this controller driver */
u16 mode_bits;
+ /* other constraints relevant to this driver */
+ u16 flags;
+#define SPI_MASTER_HALF_DUPLEX BIT(0) /* can't do full duplex */
+
/* Setup mode and clock, etc (spi driver may call many times).
*
* IMPORTANT: this may be called when transfers to another