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authorMark Brown <broonie@opensource.wolfsonmicro.com>2012-12-02 07:54:25 +0400
committerGrant Likely <grant.likely@secretlab.ca>2012-12-06 18:03:14 +0400
commitb3a223ee2d1a4635b0643c547bc0096a37334ed1 (patch)
tree0b0e7891825af66e8ecfdc6e3f14bbf2b1941991 /drivers/spi
parent266904c77911fdc0a064d97e2f06034b824c23ac (diff)
downloadlinux-b3a223ee2d1a4635b0643c547bc0096a37334ed1.tar.xz
spi: Remove SPI_BUFSIZ restriction on spi_write_then_read()
In order to avoid constantly allocating and deallocating there is a fixed buffer which spi_write_then_read() uses for transfers, with an early error check to ensure that the transfer fits within the buffer. This limits the size of transfers to this size, currently max(32, SMP_CACHE_BYTES). Since we can dynamically allocate and in fact already have a fallback to do so when there is contention for the fixed buffer remove this restriction and instead dynamically allocate a suitably sized buffer if the transfer won't fit. Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Diffstat (limited to 'drivers/spi')
-rw-r--r--drivers/spi/spi.c24
1 files changed, 11 insertions, 13 deletions
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index f1217ae59f3d..22c71e238fdf 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1545,12 +1545,18 @@ int spi_write_then_read(struct spi_device *spi,
struct spi_transfer x[2];
u8 *local_buf;
- /* Use preallocated DMA-safe buffer. We can't avoid copying here,
- * (as a pure convenience thing), but we can keep heap costs
- * out of the hot path ...
+ /* Use preallocated DMA-safe buffer if we can. We can't avoid
+ * copying here, (as a pure convenience thing), but we can
+ * keep heap costs out of the hot path unless someone else is
+ * using the pre-allocated buffer or the transfer is too large.
*/
- if ((n_tx + n_rx) > SPI_BUFSIZ)
- return -EINVAL;
+ if ((n_tx + n_rx) > SPI_BUFSIZ || !mutex_trylock(&lock)) {
+ local_buf = kmalloc(max(SPI_BUFSIZ, n_tx + n_rx), GFP_KERNEL);
+ if (!local_buf)
+ return -ENOMEM;
+ } else {
+ local_buf = buf;
+ }
spi_message_init(&message);
memset(x, 0, sizeof x);
@@ -1563,14 +1569,6 @@ int spi_write_then_read(struct spi_device *spi,
spi_message_add_tail(&x[1], &message);
}
- /* ... unless someone else is using the pre-allocated buffer */
- if (!mutex_trylock(&lock)) {
- local_buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
- if (!local_buf)
- return -ENOMEM;
- } else
- local_buf = buf;
-
memcpy(local_buf, txbuf, n_tx);
x[0].tx_buf = local_buf;
x[1].rx_buf = local_buf + n_tx;