* [PATCH] spi: Remove SPI_BUFSIZ restriction on spi_write_then_read()
@ 2012-12-02 3:54 Mark Brown
2012-12-06 0:00 ` Grant Likely
0 siblings, 1 reply; 6+ messages in thread
From: Mark Brown @ 2012-12-02 3:54 UTC (permalink / raw)
To: Grant Likely; +Cc: spi-devel-general, linux-kernel, Mark Brown
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>
---
drivers/spi/spi.c | 24 +++++++++++-------------
1 file changed, 11 insertions(+), 13 deletions(-)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index c4f7d71..224b7bc 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1646,12 +1646,18 @@ 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);
@@ -1664,14 +1670,6 @@ 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;
--
1.7.10.4
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] spi: Remove SPI_BUFSIZ restriction on spi_write_then_read()
2012-12-02 3:54 [PATCH] spi: Remove SPI_BUFSIZ restriction on spi_write_then_read() Mark Brown
@ 2012-12-06 0:00 ` Grant Likely
2012-12-06 5:37 ` Mark Brown
0 siblings, 1 reply; 6+ messages in thread
From: Grant Likely @ 2012-12-06 0:00 UTC (permalink / raw)
To: Mark Brown; +Cc: spi-devel-general, linux-kernel, Mark Brown
On Sun, 2 Dec 2012 12:54:25 +0900, Mark Brown <broonie@opensource.wolfsonmicro.com> wrote:
> 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>
Looks good to me. Probably 3.9 material though.
Acked-by: Grant Likely <grant.likely@secretlab.ca>
> ---
> drivers/spi/spi.c | 24 +++++++++++-------------
> 1 file changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index c4f7d71..224b7bc 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -1646,12 +1646,18 @@ 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);
> @@ -1664,14 +1670,6 @@ 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;
> --
> 1.7.10.4
>
--
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2012-12-07 14:04 UTC | newest]
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2012-12-02 3:54 [PATCH] spi: Remove SPI_BUFSIZ restriction on spi_write_then_read() Mark Brown
2012-12-06 0:00 ` Grant Likely
2012-12-06 5:37 ` Mark Brown
[not found] ` <20121206053732.GD10867-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>
2012-12-06 14:04 ` Grant Likely
2012-12-07 3:41 ` Mark Brown
[not found] ` <20121207034140.GB26070-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>
2012-12-07 14:04 ` Grant Likely
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