mtd: nand: denali: use non-managed kmalloc() for DMA buffer

As Russell and Lars stated in the discussion [1], using
devm_k*alloc() with DMA is not a good idea.

Let's use kmalloc (not kzalloc because no need for zero-out).
Also, allocate the buffer as late as possible because it must be
freed for any error that follows.

[1] https://lkml.org/lkml/2017/3/8/693

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
index ec5fc8da5f9a3baa172a3619794e0f52e719366c..bb2da2fd069e8aa4c9af0d9b4ff50232ff3a70cc 100644 (file)
--- a/drivers/mtd/nand/denali.c
+++ b/drivers/mtd/nand/denali.c
@@ -23,6 +23,7 @@
 #include <linux/mutex.h>
 #include <linux/mtd/mtd.h>
 #include <linux/module.h>
+#include <linux/slab.h>
 
 #include "denali.h"
 
@@ -1352,13 +1353,6 @@ int denali_init(struct denali_nand_info *denali)
        if (ret)
                goto disable_irq;
 
-       denali->buf = devm_kzalloc(denali->dev, mtd->writesize + mtd->oobsize,
-                                  GFP_KERNEL);
-       if (!denali->buf) {
-               ret = -ENOMEM;
-               goto disable_irq;
-       }
-
        if (ioread32(denali->flash_reg + FEATURES) & FEATURES__DMA)
                denali->dma_avail = 1;
 
@@ -1443,17 +1437,30 @@ int denali_init(struct denali_nand_info *denali)
        if (ret)
                goto disable_irq;
 
+       /*
+        * This buffer is DMA-mapped by denali_{read,write}_page_raw.  Do not
+        * use devm_kmalloc() because the memory allocated by devm_ does not
+        * guarantee DMA-safe alignment.
+        */
+       denali->buf = kmalloc(mtd->writesize + mtd->oobsize, GFP_KERNEL);
+       if (!denali->buf) {
+               ret = -ENOMEM;
+               goto disable_irq;
+       }
+
        ret = nand_scan_tail(mtd);
        if (ret)
-               goto disable_irq;
+               goto free_buf;
 
        ret = mtd_device_register(mtd, NULL, 0);
        if (ret) {
                dev_err(denali->dev, "Failed to register MTD: %d\n", ret);
-               goto disable_irq;
+               goto free_buf;
        }
        return 0;
 
+free_buf:
+       kfree(denali->buf);
 disable_irq:
        denali_disable_irq(denali);
 
@@ -1467,6 +1474,7 @@ void denali_remove(struct denali_nand_info *denali)
        struct mtd_info *mtd = nand_to_mtd(&denali->nand);
 
        nand_release(mtd);
+       kfree(denali->buf);
        denali_disable_irq(denali);
 }
 EXPORT_SYMBOL(denali_remove);