linux-kernel - [PATCH 4.4 055/108] mtd: nand: brcmnand: Disable prefetch by default

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Date:   Thu, 15 Feb 2018 16:16:52 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kamal Dasu <kdasu.kdev@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>
Subject: [PATCH 4.4 055/108] mtd: nand: brcmnand: Disable prefetch by default

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kamal Dasu <kdasu.kdev@...il.com>

commit f953f0f89663c39f08f4baaa8a4a881401b65654 upstream.

Brcm nand controller prefetch feature needs to be disabled
by default. Enabling affects performance on random reads as
well as dma reads.

Signed-off-by: Kamal Dasu <kdasu.kdev@...il.com>
Fixes: 27c5b17cd1b1 ("mtd: nand: add NAND driver "library" for Broadcom STB NAND controller")
Acked-by: Florian Fainelli <f.fainelli@...il.com>
Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/mtd/nand/brcmnand/brcmnand.c |   13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

--- a/drivers/mtd/nand/brcmnand/brcmnand.c
+++ b/drivers/mtd/nand/brcmnand/brcmnand.c
@@ -1922,16 +1922,9 @@ static int brcmnand_setup_dev(struct brc
 	tmp &= ~ACC_CONTROL_PARTIAL_PAGE;
 	tmp &= ~ACC_CONTROL_RD_ERASED;
 	tmp &= ~ACC_CONTROL_FAST_PGM_RDIN;
-	if (ctrl->features & BRCMNAND_HAS_PREFETCH) {
-		/*
-		 * FIXME: Flash DMA + prefetch may see spurious erased-page ECC
-		 * errors
-		 */
-		if (has_flash_dma(ctrl))
-			tmp &= ~ACC_CONTROL_PREFETCH;
-		else
-			tmp |= ACC_CONTROL_PREFETCH;
-	}
+	if (ctrl->features & BRCMNAND_HAS_PREFETCH)
+		tmp &= ~ACC_CONTROL_PREFETCH;
+
 	nand_writereg(ctrl, offs, tmp);
 
 	return 0;