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Message-ID: <20110113015545.GA7122@freescale.com>
Date: Thu, 13 Jan 2011 09:55:46 +0800
From: Shawn Guo <shawn.guo@...escale.com>
To: Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>
CC: Sascha Hauer <s.hauer@...gutronix.de>, <davem@...emloft.net>,
<gerg@...pgear.com>, <baruch@...s.co.il>, <eric@...rea.com>,
<bryan.wu@...onical.com>, <r64343@...escale.com>,
<B32542@...escale.com>, <lw@...o-electronics.de>,
<w.sang@...gutronix.de>, <jamie@...ieiles.com>,
<jamie@...reable.org>, <netdev@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 08/10] ARM: mxs: add ocotp read function
On Wed, Jan 12, 2011 at 05:01:06PM +0100, Uwe Kleine-König wrote:
> Hello Sascha,
>
> On Wed, Jan 12, 2011 at 03:50:36PM +0100, Sascha Hauer wrote:
> > On Wed, Jan 12, 2011 at 02:47:12PM +0800, Shawn Guo wrote:
> > > On Tue, Jan 11, 2011 at 02:31:37PM +0100, Sascha Hauer wrote:
> > > > On Thu, Jan 06, 2011 at 03:13:16PM +0800, Shawn Guo wrote:
> > > > > Signed-off-by: Shawn Guo <shawn.guo@...escale.com>
> > > > > ---
> > > > > Changes for v4:
> > > > > - Call cpu_relax() during polling
> > > > >
> > > > > 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
> > > > >
> > > > > diff --git a/arch/arm/mach-mxs/Makefile b/arch/arm/mach-mxs/Makefile
> > > > > index 39d3f9c..f23ebbd 100644
> > > > > --- a/arch/arm/mach-mxs/Makefile
> > > > > +++ b/arch/arm/mach-mxs/Makefile
> > > > > @@ -1,5 +1,5 @@
> > > > > # Common support
> > > > > -obj-y := clock.o devices.o gpio.o icoll.o iomux.o system.o timer.o
> > > > > +obj-y := clock.o devices.o gpio.o icoll.o iomux.o ocotp.o system.o timer.o
> > > > >
> > > > > obj-$(CONFIG_SOC_IMX23) += clock-mx23.o mm-mx23.o
> > > > > obj-$(CONFIG_SOC_IMX28) += clock-mx28.o mm-mx28.o
> > > > > diff --git a/arch/arm/mach-mxs/include/mach/common.h b/arch/arm/mach-mxs/include/mach/common.h
> > > > > index 59133eb..cf02552 100644
> > > > > --- a/arch/arm/mach-mxs/include/mach/common.h
> > > > > +++ b/arch/arm/mach-mxs/include/mach/common.h
> > > > > @@ -13,6 +13,7 @@
> > > > >
> > > > > struct clk;
> > > > >
> > > > > +extern int mxs_read_ocotp(int offset, int count, u32 *values);
> > > > > extern int mxs_reset_block(void __iomem *);
> > > > > extern void mxs_timer_init(struct clk *, int);
> > > > >
> > > > > diff --git a/arch/arm/mach-mxs/ocotp.c b/arch/arm/mach-mxs/ocotp.c
> > > > > new file mode 100644
> > > > > index 0000000..e2d39aa
> > > > > --- /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);
> > > >
> > > > This operation does not try to clear the error bit but actually clears
> > > > it...
> > > >
> > > > > +
> > > > > + /* check both BUSY and ERROR cleared */
> > > > > + while ((__raw_readl(ocotp_base) &
> > > > > + (BM_OCOTP_CTRL_BUSY | BM_OCOTP_CTRL_ERROR)) && --timeout)
> > > > > + cpu_relax();
> > > >
> > > > ...which means you do not have to poll the error bit here...
> > > >
> > > > > +
> > > > > + if (unlikely(!timeout))
> > > > > + goto error_unlock;
> > > > > +
> > > > > + /* 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)
> > > > > + cpu_relax();
> > > >
> > > > ...which means you can factor out a ocotp_wait_busy function and let the
> > > > code speak instead of the comments.
> > > >
> > > > > +
> > > > > + if (unlikely(!timeout))
> > > > > + goto error_unlock;
> > > > > +
> > > > > + for (i = 0; i < count; i++, offset += 4)
> > > > > + *values++ = __raw_readl(ocotp_base + offset);
> > > >
> > > > The registers in the ocotp are 16 byte aligned. Does it really make
> > > > sense to provide a function allowing to read the gaps between the
> > > > registers?
> > > >
> > > Good catch. The count was added to ease the consecutive otp word
> > > reading, as there is bank open/close cost for otp read. What about
> > > the following changes?
> > >
> > > int mxs_read_ocotp(unsigned offset, size_t otp_word_cnt, u32 *values)
> > > {
> > > ......
> > >
> > > for (i = 0; i < otp_word_cnt; i++, offset += 0x10)
> > > *values++ = __raw_readl(ocotp_base + offset);
> > >
> > > ......
> > > }
> >
> > I would rather make a function like this:
> >
> > static u32 ocotp[0x27];
> >
> > const u32 *mxs_get_ocotp(void)
> > {
> > static int once = 0;
> >
> > if (once)
> > return ocotp
> >
> > /* bank open */
> >
> > for (i = 0; i < 0x27; i++)
> > ocotp[i] = readl(ocotp_base + 0x20 + i * 0x10)
> >
> > /* bank_close */
> >
> > once = 1;
> >
> > return ocotp;
> which is save on UP when it's not called from irq context.
>
> Additionally I suggest a #define for 0x27 and 0x20.
>
So I will keep the mutex and not read SRK bits.
Thanks for the comments.
--
Regards,
Shawn
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