From mboxrd@z Thu Jan 1 00:00:00 1970 From: shawn.guo@freescale.com (Shawn Guo) Date: Fri, 31 Dec 2010 09:46:20 +0800 Subject: [PATCH 08/10] ARM: mxs: add ocotp read function In-Reply-To: <20101230090224.GM14221@pengutronix.de> References: <1293548155-16328-1-git-send-email-shawn.guo@freescale.com> <1293548155-16328-9-git-send-email-shawn.guo@freescale.com> <20101229112208.GB14221@pengutronix.de> <20101230084139.GC28246@freescale.com> <20101230090224.GM14221@pengutronix.de> Message-ID: <20101231014619.GF28246@freescale.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Uwe, On Thu, Dec 30, 2010 at 10:02:24AM +0100, Uwe Kleine-K?nig wrote: > Hello Shawn, > > On Thu, Dec 30, 2010 at 04:41:40PM +0800, Shawn Guo wrote: > > On Wed, Dec 29, 2010 at 12:22:08PM +0100, Uwe Kleine-K?nig 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 > > > > +#include > > > > + > > > > +#include > > > > + > > > > +#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. > maybe add a comment? "clk_enable(clk_h) can be skipped as it must be on > anyhow because ..." or similar? It's always good to document implicit > assumptions. > OK. > > > 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; > i should be size_t, too > OK. > > > > mutex_lock(&ocotp_mutex); > > > > /* clear ERROR bit anyway */ > anyway? Better?: "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 */; > > > > if (unlikely(!timeout)) > > goto error; > This goto and some more leave the critical section without unlocking the > mutex. > My bad. Thanks. > > > > /* 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; > > } > I think it's OK then. One optimisation that comes to my mind is to make > BM_OCOTP_CTRL_RD_BANK_OPEN a clk (that can depend on clk_h). This would > allow for multiple readers, but I think it's not worth the effort. > > Best regards > Uwe > > -- > Pengutronix e.K. | Uwe Kleine-K?nig | > Industrial Linux Solutions | http://www.pengutronix.de/ | > -- Regards, Shawn