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

[Uwe Kleine-König]

Hello Shawn,

On Thu, Dec 30, 2010 at 01:50:12PM +0800, Shawn Guo wrote:
> On Wed, Dec 29, 2010 at 12:22:08PM +0100, Uwe Kleine-König wrote:
> > 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?)
> > For 2. there is no check for HW_OCOTP_CTRL_ERROR which is not OK i
> > guess?!
> > 
> Will add the check. Thanks.
> 
> > (Independant of that, shouldn't the list use BM_ prefixes as you did in
> > the code?)
> > 
> Document description uses register name followed by bit-field name
> to mean the bit.
After rereading chapter 39.4 (Register Macro Usage/Naming Convention)
I wonder if the BM_ values are shifted or not.  If they are not (as I
think it is meant) your usage is inconsitent with the manual (but IMHO
sane).  sigh.

> > > +	/* approximately wait 32 hclk cycles */
> > > +	udelay(1);
> > > +
> > > +	/* poll BUSY bit becoming cleared */
> > > +	while ((__raw_readl(ocotp_base) & BM_OCOTP_CTRL_BUSY) && --timeout)
> > > +		/* nothing */;
> > > +
> > > +	if (unlikely(!timeout))
> > > +		goto error;
> > And I think you should recheck for BM_OCOTP_CTRL_RD_BANK_OPEN here (step
> > 4 from the reference manual).
> > 
> The RM says:
> 
> Poll for HW_OCOTP_CTRL_BUSY clear. When HW_OCOTP_CTRL_BUSY is clear
> and HW_OCOTP_CTRL_RD_BANK_OPEN is set, read the data from the
> appropriate memory-mapped address.
> 
> My understanding is we only need to poll busy bit clear. And the
> second sentence just tells that read operation should be working
> when bit busy clear and rd_bank_open set, which has been done
> in step 3. I also consulted the designer and was told that only
> busy clear polling is needed.
I expected to need this (shortend the names to improve readability):

	while (__raw_readl(ocotp_base) & BUSY) && --timeout);

	if (unlikely((__raw_readl(ocotp_base) & (BUSY | RDBOPEN)) != RDBOPEN))
		goto error_unlock;

*shrug*

Best regards
Uwe

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