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From: Sebastian Reichel <sre@kernel.org>
To: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Cc: Guenter Roeck <linux@roeck-us.net>,
	mazziesaccount@gmail.com, lee.jones@linaro.org,
	robh+dt@kernel.org, mark.rutland@arm.com, lgirdwood@gmail.com,
	broonie@kernel.org, gregkh@linuxfoundation.org,
	rafael@kernel.org, mturquette@baylibre.com, sboyd@kernel.org,
	linus.walleij@linaro.org, bgolaszewski@baylibre.com,
	a.zummo@towertech.it, alexandre.belloni@bootlin.com,
	wim@linux-watchdog.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org,
	linux-gpio@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-rtc@vger.kernel.org, linux-watchdog@vger.kernel.org,
	mikko.mutanen@fi.rohmeurope.com,
	heikki.haikola@fi.rohmeurope.com
Subject: Re: [RFC PATCH v1 13/13] watchdog: bd70528: Initial support for ROHM BD70528 watchdog block
Date: Wed, 23 Jan 2019 18:47:28 +0100
Message-ID: <20190123174728.uu7zhno5xea2bga7@earth.universe> (raw)
In-Reply-To: <20190122180309.GD2559@localhost.localdomain>

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Hi,

On Tue, Jan 22, 2019 at 08:03:09PM +0200, Matti Vaittinen wrote:
> On Tue, Jan 22, 2019 at 09:40:56AM -0800, Guenter Roeck wrote:
> > On Tue, Jan 22, 2019 at 07:10:23PM +0200, Matti Vaittinen wrote:
> > > On Tue, Jan 22, 2019 at 07:47:50AM -0800, Guenter Roeck wrote:
> > > > On Tue, Jan 22, 2019 at 11:48:36AM +0200, Matti Vaittinen wrote:
> > > > > Initial support for watchdog block included in ROHM BD70528
> > > > > power management IC.
> > > > > 
> > > > > Configurations for low power states are still to be checked.
> > > > > 
> > > > > Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
> > > > > ---
> > > > >  drivers/watchdog/Kconfig       |  12 +++
> > > > >  drivers/watchdog/Makefile      |   1 +
> > > > >  drivers/watchdog/bd70528_wdt.c | 161 +++++++++++++++++++++++++++++++++++++++++
> > > > >  3 files changed, 174 insertions(+)
> > > > >  create mode 100644 drivers/watchdog/bd70528_wdt.c
> > > > > 
> > > > > diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> > > > > index 57f017d74a97..f30e3a3e886e 100644
> > > > > --- a/drivers/watchdog/Kconfig
> > > > > +++ b/drivers/watchdog/Kconfig
> > > > > @@ -90,6 +90,18 @@ config SOFT_WATCHDOG_PRETIMEOUT
> > > > >  	  watchdog. Be aware that governors might affect the watchdog because it
> > > > >  	  is purely software, e.g. the panic governor will stall it!
> > > > >  
> > > > > +config BD70528_WATCHDOG
> > > > > +	tristate "ROHM BD70528 PMIC Watchdog"
> > > > > +	depends on MFD_ROHM_BD70528
> > > > > +	select WATCHDOG_CORE
> > > > > +	help
> > > > > +	  Support for the watchdog in the ROHM BD70528 PMIC. Watchdog trigger
> > > > > +	  cause system reset.
> > > > > +
> > > > > +	  Say Y here to include support for the ROHM BD70528 watchdog.
> > > > > +	  Alternatively say M to compile the driver as a module,
> > > > > +	  which will be called bd70528_wdt.
> > > > > +
> > > > >  config DA9052_WATCHDOG
> > > > >  	tristate "Dialog DA9052 Watchdog"
> > > > >  	depends on PMIC_DA9052 || COMPILE_TEST
> > > > > diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> > > > > index a0917ef28e07..1ce87a3b1172 100644
> > > > > --- a/drivers/watchdog/Makefile
> > > > > +++ b/drivers/watchdog/Makefile
> > > > > @@ -204,6 +204,7 @@ obj-$(CONFIG_WATCHDOG_SUN4V)		+= sun4v_wdt.o
> > > > >  obj-$(CONFIG_XEN_WDT) += xen_wdt.o
> > > > >  
> > > > >  # Architecture Independent
> > > > > +obj-$(CONFIG_BD70528_WATCHDOG) += bd70528_wdt.o
> > > > >  obj-$(CONFIG_DA9052_WATCHDOG) += da9052_wdt.o
> > > > >  obj-$(CONFIG_DA9055_WATCHDOG) += da9055_wdt.o
> > > > >  obj-$(CONFIG_DA9062_WATCHDOG) += da9062_wdt.o
> > > > > diff --git a/drivers/watchdog/bd70528_wdt.c b/drivers/watchdog/bd70528_wdt.c
> > > > > new file mode 100644
> > > > > index 000000000000..e9a32566f595
> > > > > --- /dev/null
> > > > > +++ b/drivers/watchdog/bd70528_wdt.c
> > > > > @@ -0,0 +1,161 @@
> > > > > +// SPDX-License-Identifier: GPL-2.0
> > > > > +// Copyright (C) 2018 ROHM Semiconductors
> > > > > +// ROHM BD70528MWV watchdog driver
> > > > > +
> > > > > +#include <linux/bcd.h>
> > > > > +#include <linux/kernel.h>
> > > > > +#include <linux/mfd/rohm-bd70528.h>
> > > > > +#include <linux/module.h>
> > > > > +#include <linux/of.h>
> > > > > +#include <linux/platform_device.h>
> > > > > +#include <linux/regmap.h>
> > > > > +#include <linux/watchdog.h>
> > > > > +
> > > > > +static int bd70528_wdt_set(struct bd70528 *bd70528, int enable)
> > > > > +{
> > > > > +	int ret;
> > > > > +
> > > > > +	if (bd70528->rtc_timer_lock)
> > > > > +		mutex_lock(bd70528->rtc_timer_lock);
> > > > 
> > > > This looks awkward. I don't think the if() is necessary.
> > > 
> > > Right. Now when only bd70528 MFD driver uses this WDT this if is not
> > > required.
> > > 
> > That doesn't warrant the conditional. It just bloats the code.
> > If there is only one user, the mutex will always be acquired.
> 
> Yep. What I meant was that the only possible parent is bd70528 MFD
> driver which always initializes the mutex pointer. So pointer should be
> always set. I can imagine some other ROHM PMIC having almost identical
> watchdog block - in which case we might want to re-use this WDT driver
> with this PMIC. And if this PMIC has no RTC, then we may not need this
> mutex. But this is all speculation and I will remove check - or see how
> this changes when I see what to do with the driver's private data.
> 
> > > > > +static const struct watchdog_info bd70528_wdt_info = {
> > > > > +	.identity = "bd70528-wdt",
> > > > > +	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
> > > > > +};
> > > > > +
> > > > > +static const struct watchdog_ops bd70528_wdt_ops = {
> > > > > +	.start		= bd70528_wdt_start,
> > > > > +	.stop		= bd70528_wdt_stop,
> > > > > +	/*
> > > > > +	 *  bd70528 WDT ping is same as enable. Eg, writing 'enable' to enabled
> > > > > +	 * WDT will restart the timeout
> > > > > +	 */
> > > > Unnecessary comment.
> > > > 
> > > 
> > > Ok. I will remove the comment if this is obvious to others. For me it
> > > was not obvious. I was first writing a separate ping and start functions
> > > untill I realized that it is the same operation. But this was my first
> > > WDT driver so I don't know if this is a normal for all WDTs.
> > > 
> > It is documented as part of the API.
> I'd better read the documentation then. Thanks for pointing this out.
> I'll remove the comment.
> 
> > > > > +static int bd70528_wdt_probe(struct platform_device *pdev)
> > > > > +{
> > > > > +	struct bd70528 *tmp;
> > > > > +	struct bd70528 *bd70528;
> > > > > +	int ret;
> > > > > +
> > > > > +	tmp = dev_get_drvdata(pdev->dev.parent);
> > > > > +	if (!tmp) {
> > > > > +		dev_err(&pdev->dev, "No MFD driver data\n");
> > > > > +		return -EINVAL;
> > > > > +	}
> > > > > +	bd70528 = devm_kzalloc(&pdev->dev, sizeof(*bd70528), GFP_KERNEL);
> > > > > +	if (!bd70528)
> > > > > +		return -ENOMEM;
> > > > > +
> > > > > +	*bd70528 = *tmp;
> > > > > +	bd70528->chip.dev = &pdev->dev;
> > > > 
> > > > This is wrong.
> > > > You should not copy the parent's driver data but have local driver
> > > > data as needed which then points to the parent's driver data if
> > > > needed. I assume this is why the mutex is a pointer, but that
> > > > just shows that the whole approach is wrong.
> > > 
> > > Mutex is a pointer because we want to use same mutex from WDT and RTC.
> > > We can sure point to parent data but then we still need our own dev
> > > pointer. So we can have a struct with pointer to parent data and dev
> > > pointer - but I'm not at all sure it is any clearer.
> > 
> > As I said, that is wrong. To say it in plaintext, I won't accept
> > the driver if it copies the parent's driver data. The driver should
> > have and use its own driver data, and only maintain a pointer to
> > its parent's driver data. And most definitely you don't want to
> > copy and use any device data structure from the parent.
> 
> Allright. At the moment the WDT driver only needs regmap pointer from
> parent. I'm not sure if it will later need DT or "chip type" - but I
> will change this.

You probably want to use this:

dev_get_regmap(pdev->dev.parent, NULL);

-- Sebastian

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  reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-22  9:41 [RFC PATCH v1 00/13] support ROHM BD70528 PMIC Matti Vaittinen
2019-01-22  9:42 ` [RFC PATCH v1 01/13] regmap: regmap-irq: Add main status register support Matti Vaittinen
2019-01-23 15:55   ` Mark Brown
2019-01-22  9:42 ` [RFC PATCH v1 02/13] mfd: bd718x7.h split to ROHM common and bd718x7 specific parts Matti Vaittinen
2019-01-22  9:43 ` [RFC PATCH v1 03/13] regulator: bd718x7 use chip specific and generic data structs Matti Vaittinen
2019-01-23 15:51   ` Mark Brown
2019-01-24  7:16     ` Matti Vaittinen
2019-01-24 10:24       ` Mark Brown
2019-01-22  9:44 ` [RFC PATCH v1 04/13] clk: bd718x7: " Matti Vaittinen
2019-01-22  9:44 ` [RFC PATCH v1 05/13] mfd: bd70528: Support ROHM bd70528 PMIC - core Matti Vaittinen
2019-01-22 14:51   ` Guenter Roeck
2019-01-22 16:20     ` Matti Vaittinen
2019-01-22  9:45 ` [RFC PATCH v1 06/13] clk: bd718x7: Support ROHM BD70528 clk block Matti Vaittinen
2019-01-22  9:45 ` [RFC PATCH v1 07/13] devicetree: bindings: Document first ROHM BD70528 bindings Matti Vaittinen
2019-02-23  0:30   ` Rob Herring
2019-02-28  6:49     ` Matti Vaittinen
2019-02-28 15:37       ` Rob Herring
2019-01-22  9:46 ` [RFC PATCH v1 08/13] regulator: bd70528: Support ROHM BD70528 regulator block Matti Vaittinen
2019-01-22  9:46 ` [RFC PATCH v1 09/13] devicetree: bindings: ROHM bd70528 regulator bindings Matti Vaittinen
2019-01-22  9:47 ` [RFC PATCH v1 10/13] gpio: Initial support for ROHM bd70528 GPIO block Matti Vaittinen
2019-01-22  9:47 ` [RFC PATCH v1 11/13] rtc: bd70528: Initial support for ROHM bd70528 RTC Matti Vaittinen
2019-01-22 14:48   ` Guenter Roeck
2019-01-22 16:29     ` Matti Vaittinen
2019-01-22  9:48 ` [RFC PATCH v1 12/13] power: supply: Initial support for ROHM BD70528 PMIC charger block Matti Vaittinen
2019-01-22  9:48 ` [RFC PATCH v1 13/13] watchdog: bd70528: Initial support for ROHM BD70528 watchdog block Matti Vaittinen
2019-01-22 15:47   ` Guenter Roeck
2019-01-22 17:10     ` Matti Vaittinen
2019-01-22 17:40       ` Guenter Roeck
2019-01-22 18:03         ` Matti Vaittinen
2019-01-23 17:47           ` Sebastian Reichel [this message]
2019-01-24 10:44             ` Matti Vaittinen
2019-01-24 14:37               ` Guenter Roeck

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