On Fri, Jul 20, 2018 at 08:23:44PM +0100, Ben Hutchings wrote:
On Sun, 2018-07-01 at 18:02 +0200, Greg Kroah-Hartman wrote:
4.4-stable review patch. If anyone has any objections, please let me know.
From: Maxime Chevallier maxime.chevallier@bootlin.com
commit ce99319a182fe766be67f96338386f3ec73e321c upstream.
When SPI transfers can be offloaded using DMA, the SPI core need to build a scatterlist to make sure that the buffer to be transferred is dma-able.
This patch fixes the scatterlist entry size computation in the case where the maximum acceptable scatterlist entry supported by the DMA controller is less than PAGE_SIZE, when the buffer is vmalloced.
For each entry, the actual size is given by the minimum between the desc_len (which is the max buffer size supported by the DMA controller) and the remaining buffer length until we cross a page boundary.
Fixes: 65598c13fd66 ("spi: Fix per-page mapping of unaligned vmalloc-ed buffer") Signed-off-by: Maxime Chevallier maxime.chevallier@bootlin.com Signed-off-by: Mark Brown broonie@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Sudip Mukherjee sudipm.mukherjee@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
drivers/spi/spi.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
--- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -707,8 +707,14 @@ static int spi_map_buf(struct spi_master for (i = 0; i < sgs; i++) { if (vmalloced_buf) {
min = min_t(size_t,len, desc_len - offset_in_page(buf));
/** Next scatterlist entry size is the minimum between* the desc_len and the remaining buffer length that* fits in a page.*/min = min_t(size_t, desc_len,min_t(size_t, len,PAGE_SIZE - offset_in_page(buf)));vm_page = vmalloc_to_page(buf); if (!vm_page) { sg_free_table(sgt);
I think this makes sense upstream, but in 4.4 it seems to be a no-op since desc_len is always set to PAGE_SIZE when vmalloced_buf is true. This fix depends on (at least) commit df88e91bbfd1 "spi: respect the maximum segment size of DMA device" which went into 4.6.
Good catch. I'll leave it as-is for now though.
thanks,
greg k-h