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

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.chevall...@bootlin.com>
 drivers/spi/spi.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index b33a727a0158..4153f959f28c 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -779,8 +779,14 @@ static int spi_map_buf(struct spi_controller *ctlr, struct 
device *dev,
        for (i = 0; i < sgs; i++) {
                if (vmalloced_buf || kmap_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)));
                        if (vmalloced_buf)
                                vm_page = vmalloc_to_page(buf);

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