linux-kernel - [PATCH v2 6/8] staging: fsl-mc: don't use raw device io functions

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Date:   Tue, 18 Jul 2017 16:37:21 +0300
From:   <laurentiu.tudor@....com>
To:     <gregkh@...uxfoundation.org>, <stuyoder@...il.com>
CC:     <devel@...verdev.osuosl.org>, <linux-kernel@...r.kernel.org>,
        <marc.zyngier@....com>, <agraf@...e.de>, <robin.murphy@....com>,
        <arnd@...db.de>, <ioana.ciornei@....com>,
        <ruxandra.radulescu@....com>, <bharat.bhushan@....com>,
        <catalin.horghidan@....com>, <leoyang.li@....com>,
        <roy.pledge@....com>, <linux-arm-kernel@...ts.infradead.org>,
        Laurentiu Tudor <laurentiu.tudor@....com>
Subject: [PATCH v2 6/8] staging: fsl-mc: don't use raw device io functions

From: Laurentiu Tudor <laurentiu.tudor@....com>

As raw device io functions are not portable and don't handle byte-order
(triggering suspicion that endianness isn't handled well) switch to
using the standard api.
Since MC expects LE byte-order and the upper layers already take care
of that, we need to trick the device io api by doing a LE -> CPU
conversion just before calling it. This way, the CPU -> LE conversion
done in the api puts the data back in the right byte-order. Obviously,
for reads the extra step is mirrored: there's a CPU -> LE conversion
following the API call.

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
---
Notes:
    -v2
      -new patch replacing https://lkml.org/lkml/2017/7/17/419

 drivers/staging/fsl-mc/bus/mc-sys.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/fsl-mc/bus/mc-sys.c b/drivers/staging/fsl-mc/bus/mc-sys.c
index 195d9f3..8a6dc47 100644
--- a/drivers/staging/fsl-mc/bus/mc-sys.c
+++ b/drivers/staging/fsl-mc/bus/mc-sys.c
@@ -126,12 +126,15 @@ static inline void mc_write_command(struct mc_command __iomem *portal,
 
 	/* copy command parameters into the portal */
 	for (i = 0; i < MC_CMD_NUM_OF_PARAMS; i++)
-		__raw_writeq(cmd->params[i], &portal->params[i]);
-	/* ensure command params are committed before submitting it */
-	wmb();
+		/*
+		 * Data is already in the expected LE byte-order. Do an
+		 * extra LE -> CPU conversion so that the CPU -> LE done in
+		 * the device io write api puts it back in the right order.
+		 */
+		writeq_relaxed(le64_to_cpu(cmd->params[i]), &portal->params[i]);
 
 	/* submit the command by writing the header */
-	__raw_writeq(cmd->header, &portal->header);
+	writeq(le64_to_cpu(cmd->header), &portal->header);
 }
 
 /**
@@ -151,14 +154,20 @@ static inline enum mc_cmd_status mc_read_response(struct mc_command __iomem *
 	enum mc_cmd_status status;
 
 	/* Copy command response header from MC portal: */
-	resp->header = __raw_readq(&portal->header);
+	resp->header = cpu_to_le64(readq_relaxed(&portal->header));
 	status = mc_cmd_hdr_read_status(resp);
 	if (status != MC_CMD_STATUS_OK)
 		return status;
 
 	/* Copy command response data from MC portal: */
 	for (i = 0; i < MC_CMD_NUM_OF_PARAMS; i++)
-		resp->params[i] = __raw_readq(&portal->params[i]);
+		/*
+		 * Data is expected to be in LE byte-order. Do an
+		 * extra CPU -> LE to revert the LE -> CPU done in
+		 * the device io read api.
+		 */
+		resp->params[i] =
+			cpu_to_le64(readq_relaxed(&portal->params[i]));
 
 	return status;
 }
-- 
2.9.4