[PATCH] mtd: spi-nor-core: Implement spi_nor_read_sfdp_dma_unsafe() for sfdp parse

[Vaishnav Achath]

During SFDP header parse and BFPT parse, structures in stack are used
to perform spi_nor_read_sfdp() which expects a dma-safe buffer.

This commit introduces spi_nor_read_sfdp_dma_unsafe() to wrap
spi_nor_read_sfdp() using a kmalloc'ed bounce buffer which is
the same implementation in Linux (drivers/mtd/spi-nor/sfdp.c).

Signed-off-by: Vaishnav Achath <vaishna...@ti.com>
---
 drivers/mtd/spi/spi-nor-core.c | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
index 3b7c817c02..90d05da1d8 100644
--- a/drivers/mtd/spi/spi-nor-core.c
+++ b/drivers/mtd/spi/spi-nor-core.c
@@ -2022,6 +2022,36 @@ read_err:
        return ret;
 }
 
+/**
+ * spi_nor_read_sfdp_dma_unsafe() - read Serial Flash Discoverable Parameters.
+ * @nor:       pointer to a 'struct spi_nor'
+ * @addr:      offset in the SFDP area to start reading data from
+ * @len:       number of bytes to read
+ * @buf:       buffer where the SFDP data are copied into
+ *
+ * Wrap spi_nor_read_sfdp() using a kmalloc'ed bounce buffer as @buf is now not
+ * guaranteed to be dma-safe.
+ *
+ * Return: -ENOMEM if kmalloc() fails, the return code of spi_nor_read_sfdp()
+ *          otherwise.
+ */
+static int spi_nor_read_sfdp_dma_unsafe(struct spi_nor *nor, u32 addr,
+                                       size_t len, void *buf)
+{
+       void *dma_safe_buf;
+       int ret;
+
+       dma_safe_buf = kmalloc(len, GFP_KERNEL);
+       if (!dma_safe_buf)
+               return -ENOMEM;
+
+       ret = spi_nor_read_sfdp(nor, addr, len, dma_safe_buf);
+       memcpy(buf, dma_safe_buf, len);
+       kfree(dma_safe_buf);
+
+       return ret;
+}
+
 /* Fast Read settings. */
 
 static void
@@ -2195,7 +2225,7 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
                    bfpt_header->length * sizeof(u32));
        addr = SFDP_PARAM_HEADER_PTP(bfpt_header);
        memset(&bfpt, 0, sizeof(bfpt));
-       err = spi_nor_read_sfdp(nor,  addr, len, &bfpt);
+       err = spi_nor_read_sfdp_dma_unsafe(nor,  addr, len, &bfpt);
        if (err < 0)
                return err;
 
@@ -2480,7 +2510,7 @@ static int spi_nor_parse_sfdp(struct spi_nor *nor,
        int i, err;
 
        /* Get the SFDP header. */
-       err = spi_nor_read_sfdp(nor, 0, sizeof(header), &header);
+       err = spi_nor_read_sfdp_dma_unsafe(nor, 0, sizeof(header), &header);
        if (err < 0)
                return err;
 
-- 
2.17.1