[PATCH 08/10] ARM: mxs: add ocotp read function

[Shawn Guo]

On Wed, Dec 29, 2010 at 12:22:08PM +0100, Uwe Kleine-König wrote:
> Hello,
> 
> On Tue, Dec 28, 2010 at 10:55:53PM +0800, Shawn Guo wrote:
> > diff --git a/arch/arm/mach-mxs/ocotp.c b/arch/arm/mach-mxs/ocotp.c
> > new file mode 100644
> > index 0000000..24457d7
> > --- /dev/null
> > +++ b/arch/arm/mach-mxs/ocotp.c
> > @@ -0,0 +1,52 @@
> > +/*
> > + * 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 <mach/mxs.h>
> > +
> > +#define BM_OCOTP_CTRL_RD_BANK_OPEN	(1 << 12)
> > +#define BM_OCOTP_CTRL_BUSY		(1 << 8)
> > +
> > +int mxs_read_ocotp(int offset, int count, u32 *values)
> > +{
> > +	void __iomem *ocotp_base = MXS_IO_ADDRESS(MXS_OCOTP_BASE_ADDR);
> > +	int i, timeout = 0x400;
> > +
> > +	/* open OCOTP banks for read */
> > +	__mxs_setl(BM_OCOTP_CTRL_RD_BANK_OPEN, ocotp_base);
> The reference manual specifies:
> 	1. Program the HCLK to a frequency up to the maximum allowable HCLK
> 	   frequency. [...]
> 	2. Check that HW_OCOTP_CTRL_BUSY and HW_OCOTP_CTRL_ERROR are clear.
> 	3. Set HW_OCOTP_CTRL_RD_BANK_OPEN. [...]
> 
> 1. isn't done (which is probably OK, or should it aquire a clk?)
ocotp needs clk_h, which must be on when system is running.

> For 2. there is no check for HW_OCOTP_CTRL_ERROR which is not OK i
> guess?!
> 
How does the new code look to you?

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 i, timeout = 0x400;

	mutex_lock(&ocotp_mutex);

	/* clear ERROR bit anyway */
	__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 */;

	if (unlikely(!timeout))
		goto error;

	/* open OCOTP banks for read */
	__mxs_setl(BM_OCOTP_CTRL_RD_BANK_OPEN, ocotp_base);

	/* approximately wait 32 hclk cycles */
	udelay(1);

	/* poll BUSY bit becoming cleared */
	timeout = 0x400;
	while ((__raw_readl(ocotp_base) & BM_OCOTP_CTRL_BUSY) && --timeout)
		/* nothing */;

	if (unlikely(!timeout))
		goto error;

	for (i = 0; i < count; i++, offset += 4)
		*values++ = __raw_readl(ocotp_base + offset);

	/* close banks for power saving */
	__mxs_clrl(BM_OCOTP_CTRL_RD_BANK_OPEN, ocotp_base);

	mutex_unlock(&ocotp_mutex);

	return 0;

error:
	pr_err("%s: timeout in reading OCOTP\n", __func__);
	return -ETIMEDOUT;
}

-- 
Regards,
Shawn