linux-kernel - [PATCH 3.2 84/92] dma: mv_xor: Flush descriptors before activating a channel

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Message-ID: <lsq.1402104389.393624387@decadent.org.uk>
Date:	Sat, 07 Jun 2014 02:26:29 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Lior Amsalem" <alior@...vell.com>,
	"Ezequiel Garcia" <ezequiel.garcia@...e-electrons.com>,
	"Dan Williams" <dan.j.williams@...el.com>
Subject: [PATCH 3.2 84/92] dma: mv_xor: Flush descriptors before
 activating a channel

3.2.60-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>

commit 5a9a55bf9157d3490b0c8c4c81d4708602c26e07 upstream.

We need to use writel() instead of writel_relaxed() when starting
a channel, to ensure all the descriptors have been flushed before
the activation.

While at it, remove the unneeded read-modify-write and make the
code simpler.

Signed-off-by: Lior Amsalem <alior@...vell.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
[bwh: Backported to 3.2: it was using __raw_readl() and __raw_writel()
 which are just as wrong]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/dma/mv_xor.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/drivers/dma/mv_xor.c
+++ b/drivers/dma/mv_xor.c
@@ -218,12 +218,10 @@ static void mv_set_mode(struct mv_xor_ch
 
 static void mv_chan_activate(struct mv_xor_chan *chan)
 {
-	u32 activation;
-
 	dev_dbg(chan->device->common.dev, " activate chan.\n");
-	activation = __raw_readl(XOR_ACTIVATION(chan));
-	activation |= 0x1;
-	__raw_writel(activation, XOR_ACTIVATION(chan));
+
+	/* writel ensures all descriptors are flushed before activation */
+	writel(BIT(0), XOR_ACTIVATION(chan));
 }
 
 static char mv_chan_is_busy(struct mv_xor_chan *chan)

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