On Sun, 2 Dec 2012 12:54:25 +0900, Mark Brown
<broo...@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 <broo...@opensource.wolfsonmicro.com>
Looks good to me. Probably 3.9 material though.
Acked-by: Grant Likely <grant.lik...@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.
------------------------------------------------------------------------------
LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial
Remotely access PCs and mobile devices and provide instant support
Improve your efficiency, and focus on delivering more value-add services
Discover what IT Professionals Know. Rescue delivers
http://p.sf.net/sfu/logmein_12329d2d
_______________________________________________
spi-devel-general mailing list
spi-devel-general@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/spi-devel-general
