spi: Add support to handle kmap'd buffers in spi_map_buf()

JFFS2 FS might sometime provide kmap'd buffers as destination
buffers to read data from flash. Update spi_map_buf() function to
generate sg_list for such buffers, so that SPI controllers drivers can
use DMA to read data into such buffers.

Signed-off-by: Vignesh R <vigneshr@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 14 insertions, 3 deletions

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 51ad42fad567..2a5dd22efa34 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -37,6 +37,7 @@
 #include <linux/kthread.h>
 #include <linux/ioport.h>
 #include <linux/acpi.h>
+#include <linux/highmem.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/spi.h>
@@ -709,6 +710,13 @@ static int spi_map_buf(struct spi_master *master, struct device *dev,
 {
         const bool vmalloced_buf = is_vmalloc_addr(buf);
         unsigned int max_seg_size = dma_get_max_seg_size(dev);
+#ifdef CONFIG_HIGHMEM
+        const bool kmap_buf = ((unsigned long)buf >= PKMAP_BASE &&
+                                (unsigned long)buf < (PKMAP_BASE +
+                                        (LAST_PKMAP * PAGE_SIZE)));
+#else
+        const bool kmap_buf = false;
+#endif
         int desc_len;
         int sgs;
         struct page *vm_page;
@@ -716,7 +724,7 @@ static int spi_map_buf(struct spi_master *master, struct device *dev,
         size_t min;
         int i, ret;
 
-        if (vmalloced_buf) {
+        if (vmalloced_buf || kmap_buf) {
                 desc_len = min_t(int, max_seg_size, PAGE_SIZE);
                 sgs = DIV_ROUND_UP(len + offset_in_page(buf), desc_len);
         } else if (virt_addr_valid(buf)) {
@@ -732,10 +740,13 @@ static int spi_map_buf(struct spi_master *master, struct device *dev,
 
         for (i = 0; i < sgs; i++) {
 
-                if (vmalloced_buf) {
+                if (vmalloced_buf || kmap_buf) {
                         min = min_t(size_t,
                                     len, desc_len - offset_in_page(buf));
-                        vm_page = vmalloc_to_page(buf);
+                        if (vmalloced_buf)
+                                vm_page = vmalloc_to_page(buf);
+                        else
+                                vm_page = kmap_to_page(buf);
                         if (!vm_page) {
                                 sg_free_table(sgt);
                                 return -ENOMEM;