Date: Mon, 19 Jun 2017 16:33:55 +0200
From: Oleksij Rempel <ore@pengutronix.de>
To: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Oleksij Rempel <o.rempel@pengutronix.de>, devicetree@vger.kernel.org,
        kernel@pengutronix.de, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, Mark Rutland <mark.rutland@arm.com>,
        Maxime Ripard <maxime.ripard@free-electrons.com>,
        Rob Herring <robh+dt@kernel.org>, Shawn Guo <shawnguo@kernel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Subject: Re: [PATCH v5 2/3] nvmem: add snvs_lpgpr driver
Message-ID: <20170619143355.2qeuetsx2pbvlgng@pengutronix.de>
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 <20170609125730.25502-3-o.rempel@pengutronix.de>
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Hi Stefan,

On Fri, Jun 09, 2017 at 05:01:09PM +0200, Stefan Wahren wrote:
> Hi Oleksij,
> 
> please add the NXP guys in CC in order to give them a chance to review.
> 
> Am 09.06.2017 um 14:57 schrieb Oleksij Rempel:
> > This is a driver for Low Power General Purpose Register (LPGPR)
> > available on i.MX6 SoCs in Secure Non-Volatile Storage (SNVS)
> > of this chip.
> >
> > It is a 32-bit read/write register located in the low power domain.
> > Since LPGPR is located in the battery-backed power domain, LPGPR can
> > be used by any application for retaining data during an SoC power-down
> > mode.
> >
> > Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> > ---
> >  drivers/nvmem/Kconfig      |  10 ++++
> >  drivers/nvmem/Makefile     |   2 +
> >  drivers/nvmem/snvs_lpgpr.c | 138 +++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 150 insertions(+)
> >  create mode 100644 drivers/nvmem/snvs_lpgpr.c
> >
> > diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
> > index 101ced4c84be..ea3044c5d6ee 100644
> > --- a/drivers/nvmem/Kconfig
> > +++ b/drivers/nvmem/Kconfig
> > @@ -144,4 +144,14 @@ config MESON_EFUSE
> >  	  This driver can also be built as a module. If so, the module
> >  	  will be called nvmem_meson_efuse.
> >  
> > +config NVMEM_SNVS_LPGPR
> > +	tristate "Support for Low Power General Purpose Register"
> > +	depends on SOC_IMX6 || COMPILE_TEST
> > +	help
> > +	  This is a driver for Low Power General Purpose Register (LPGPR) available on
> > +	  i.MX6 SoCs in Secure Non-Volatile Storage (SNVS) of this chip.
> > +
> > +	  This driver can also be built as a module. If so, the module
> > +	  will be called nvmem-snvs-lpgpr.
> > +
> >  endif
> > diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
> > index 173140658693..4c589184acee 100644
> > --- a/drivers/nvmem/Makefile
> > +++ b/drivers/nvmem/Makefile
> > @@ -30,3 +30,5 @@ obj-$(CONFIG_NVMEM_VF610_OCOTP)	+= nvmem-vf610-ocotp.o
> >  nvmem-vf610-ocotp-y		:= vf610-ocotp.o
> >  obj-$(CONFIG_MESON_EFUSE)	+= nvmem_meson_efuse.o
> >  nvmem_meson_efuse-y		:= meson-efuse.o
> > +obj-$(CONFIG_NVMEM_SNVS_LPGPR)	+= nvmem_snvs_lpgpr.o
> > +nvmem_snvs_lpgpr-y		:= snvs_lpgpr.o
> > diff --git a/drivers/nvmem/snvs_lpgpr.c b/drivers/nvmem/snvs_lpgpr.c
> > new file mode 100644
> > index 000000000000..acb3ddc0d990
> > --- /dev/null
> > +++ b/drivers/nvmem/snvs_lpgpr.c
> > @@ -0,0 +1,138 @@
> > +/*
> > + * Copyright (c) 2015 Pengutronix, Steffen Trumtrar <kernel@pengutronix.de>
> > + * Copyright (c) 2017 Pengutronix, Oleksij Rempel <kernel@pengutronix.de>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2
> > + * as published by the Free Software Foundation.
> > + */
> > +
> > +#include <linux/mfd/syscon.h>
> > +#include <linux/module.h>
> > +#include <linux/nvmem-provider.h>
> > +#include <linux/of_device.h>
> > +#include <linux/regmap.h>
> > +
> > +struct snvs_lpgpr_cfg {
> > +	int offset;
> > +};
> > +
> > +struct snvs_lpgpr_priv {
> > +	struct device_d			*dev;
> > +	struct regmap			*regmap;
> > +	struct nvmem_config		cfg;
> > +	const struct snvs_lpgpr_cfg	*dcfg;
> > +};
> > +
> > +static const struct snvs_lpgpr_cfg snvs_lpgpr_cfg_imx6q = {
> > +	.offset = 0x68,
> > +};
> > +
> > +static int snvs_lpgpr_write(void *context, unsigned int offset, void *_val,
> > +			    size_t bytes)
> > +{
> > +	struct snvs_lpgpr_priv *priv = context;
> > +	const struct snvs_lpgpr_cfg *dcfg = priv->dcfg;
> > +	const u32 *val = _val;
> > +	int i = 0, words = bytes / 4;
> > +
> > +	while (words--)
> > +		regmap_write(priv->regmap, dcfg->offset + offset + (i++ * 4),
> > +			     *val++);
> 
> according to the reference manual "57.9.14 SNVS_LP General Purpose
> Register (SNVS_LPGPR)":
> 
>     When GPR_SL or GPR_HL bit is set, the register cannot be programmed.
> 
> I think the driver should handle this error case properly.

good point,
I'll update it.

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