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

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=7d370b2c255612569818134ae0a6d0e46eabfe8b
Commit:     7d370b2c255612569818134ae0a6d0e46eabfe8b
Parent:     997cde2a222091270ce0c276e567b68e5615f577
Author:     Masahiro Yamada <yamada.masahiro at socionext.com>
AuthorDate: Tue Jun 13 22:45:48 2017 +0900
Committer:  Boris Brezillon <boris.brezillon at free-electrons.com>
CommitDate: Tue Jun 20 09:14:53 2017 +0200

    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 at socionext.com>
    Cc: Russell King <rmk+kernel at armlinux.org.uk>
    Cc: Lars-Peter Clausen <lars at metafoo.de>
    Acked-by: Robin Murphy <robin.murphy at arm.com>
    Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>
---
 drivers/mtd/nand/denali.c | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
index ec5fc8d..bb2da2f 100644
--- 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);