Messages in this thread Patch in this message | | | Date | Thu, 30 Apr 2009 09:56:26 -0700 | From | Greg KH <> | Subject | [patch 37/88] spi: spi_write_then_read() bugfixes |
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2.6.28-stable review patch. If anyone has any objections, please let us know.
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From: David Brownell <dbrownell@users.sourceforge.net>
upstream commit: bdff549ebeff92b1a6952e5501caf16a6f8898c8
The "simplify spi_write_then_read()" patch included two regressions from the 2.6.27 behaviors:
- The data it wrote out during the (full duplex) read side of the transfer was not zeroed.
- It fails completely on half duplex hardware, such as Microwire and most "3-wire" SPI variants.
So, revert that patch. A revised version should be submitted at some point, which can get the speedup on standard hardware (full duplex) without breaking on less-capable half-duplex stuff.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> --- drivers/spi/spi.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-)
--- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -660,7 +660,7 @@ int spi_write_then_read(struct spi_devic int status; struct spi_message message; - struct spi_transfer x; + struct spi_transfer x[2]; u8 *local_buf; /* Use preallocated DMA-safe buffer. We can't avoid copying here, @@ -671,9 +671,15 @@ int spi_write_then_read(struct spi_devic return -EINVAL; spi_message_init(&message); - memset(&x, 0, sizeof x); - x.len = n_tx + n_rx; - spi_message_add_tail(&x, &message); + memset(x, 0, sizeof x); + if (n_tx) { + x[0].len = n_tx; + spi_message_add_tail(&x[0], &message); + } + if (n_rx) { + x[1].len = n_rx; + spi_message_add_tail(&x[1], &message); + } /* ... unless someone else is using the pre-allocated buffer */ if (!mutex_trylock(&lock)) { @@ -684,15 +690,15 @@ int spi_write_then_read(struct spi_devic local_buf = buf; memcpy(local_buf, txbuf, n_tx); - x.tx_buf = local_buf; - x.rx_buf = local_buf; + x[0].tx_buf = local_buf; + x[1].rx_buf = local_buf + n_tx; /* do the i/o */ status = spi_sync(spi, &message); if (status == 0) - memcpy(rxbuf, x.rx_buf + n_tx, n_rx); + memcpy(rxbuf, x[1].rx_buf, n_rx); - if (x.tx_buf == buf) + if (x[0].tx_buf == buf) mutex_unlock(&lock); else kfree(local_buf);
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