Hello Jamie,

On Wed, Jan 05, 2011 at 04:16:46PM +0000, Jamie Iles wrote:

On Wed, Jan 05, 2011 at 10:07:35PM +0800, Shawn Guo wrote:

quoted

Signed-off-by: Shawn Guo <redacted>
---
Changes for v2:
 - Add mutex locking for mxs_read_ocotp()
 - Use type size_t for count and i
 - Add comment for clk_enable/disable skipping
 - Add ERROR bit clearing and polling step

 arch/arm/mach-mxs/Makefile              |    2 +-
 arch/arm/mach-mxs/include/mach/common.h |    1 +
 arch/arm/mach-mxs/ocotp.c               |   79 +++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+), 1 deletions(-)
 create mode 100644 arch/arm/mach-mxs/ocotp.c

[...]

quoted

diff --git a/arch/arm/mach-mxs/ocotp.c b/arch/arm/mach-mxs/ocotp.c
new file mode 100644
index 0000000..902ef59
--- /dev/null
+++ b/arch/arm/mach-mxs/ocotp.c

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2010 Freescale Semiconductor, Inc. All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+
+#include <mach/mxs.h>
+
+#define BM_OCOTP_CTRL_BUSY		(1 << 8)
+#define BM_OCOTP_CTRL_ERROR		(1 << 9)
+#define BM_OCOTP_CTRL_RD_BANK_OPEN	(1 << 12)
+
+static DEFINE_MUTEX(ocotp_mutex);
+
+int mxs_read_ocotp(unsigned offset, size_t count, u32 *values)
+{
+	void __iomem *ocotp_base = MXS_IO_ADDRESS(MXS_OCOTP_BASE_ADDR);
+	int timeout = 0x400;
+	size_t i;
+
+	mutex_lock(&ocotp_mutex);
+
+	/*
+	 * clk_enable(hbus_clk) for ocotp can be skipped
+	 * as it must be on when system is running.
+	 */
+
+	/* try to clear ERROR bit */
+	__mxs_clrl(BM_OCOTP_CTRL_ERROR, ocotp_base);
+
+	/* check both BUSY and ERROR cleared */
+	while ((__raw_readl(ocotp_base) &
+		(BM_OCOTP_CTRL_BUSY | BM_OCOTP_CTRL_ERROR)) && --timeout)
+		/* nothing */;

Is it worth using cpu_relax() in these polling loops?

I don't know what cpu_relax does for other platforms, but on ARM it's
just a memory barrier which AFAICT doesn't help here at all (which
doesn't need to be correct).  Why do you think it would be better?

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-König            |
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