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From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Mark Brown <broonie@kernel.org>
Cc: Hans de Goede <hdegoede@redhat.com>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	Mark Gross <markgross@kernel.org>,
	Andy Shevchenko <andy@infradead.org>,
	Wolfram Sang <wsa@the-dreams.de>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Daniel Scally <djrscally@gmail.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>, Len Brown <lenb@kernel.org>,
	linux-acpi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Kate Hsuan <hpa@redhat.com>,
	linux-media@vger.kernel.org, linux-clk@vger.kernel.org,
	Andy Shevchenko <andy.shevchenko@gmail.com>
Subject: Re: [PATCH v6 05/15] regulator: Introduce tps68470-regulator driver
Date: Mon, 29 Nov 2021 17:35:20 +0200	[thread overview]
Message-ID: <YaTzOA7uV5TzHDDR@pendragon.ideasonboard.com> (raw)
In-Reply-To: <YaTCpgYaPDssQp+N@sirena.org.uk>

Hi Mark,

On Mon, Nov 29, 2021 at 12:08:06PM +0000, Mark Brown wrote:
> On Sun, Nov 28, 2021 at 01:38:34AM +0200, Laurent Pinchart wrote:
> > On Fri, Nov 26, 2021 at 12:22:35PM +0100, Hans de Goede wrote:
> > > On 11/26/21 00:32, Laurent Pinchart wrote:
> > > > On Thu, Nov 25, 2021 at 05:54:02PM +0100, Hans de Goede wrote:
> > > >> The TPS68470 PMIC provides Clocks, GPIOs and Regulators. At present in
> > > >> the kernel the Regulators and Clocks are controlled by an OpRegion
> > > >> driver designed to work with power control methods defined in ACPI, but
> 
> Please delete unneeded context from mails when replying.  Doing this
> makes it much easier to find your reply in the message, helping ensure
> it won't be missed by people scrolling through the irrelevant quoted
> material.

I have mixed feelings about that, someones the context is indeed not
needed, but I've found myself more often than not replying deep in a
mail thread and wishing the context hadn't been deleted, because it
ended up being relevant.

> > > >> + * (1) This regulator must have the same voltage as VIO if S_IO LDO is used to
> > > >> + *     power a sensor/VCM which I2C is daisy chained behind the PMIC.
> > > >> + * (2) If there is no I2C daisy chain it can be set freely.
> > > >> + */
> 
> > > > Do we need safety checks for this ?
> 
> > > There really is no way to deal this condition needs to matches inside the driver,
> > > this should be enforced by setting proper constraints on the 2 regulators where
> > > the PMIC is used with a sensor I2C daisy chained behind it.
> 
> > Right. I tend to be cautious here, as incorrect settings can destroy the
> > hardware. We should err on the side of too many safety checks rather
> > than too few. I was thinking that the cio2-bridge driver could set a
> > daisy-chaining flag, which could trigger additional checks here, but it
> > wouldn't protect against someone experimenting to support a new device
> > and setting different voltages without the daisy-chaining flag.
> 
> > My biggest worry is that someone with an unsupported machine may start
> > by copying and pasting an existing configuration to try it out, and fry
> > their hardware.
> 
> There's really nothing you can do that prevents this, especially in the
> cut'n'paste scenario.  Overrides tend to get copied along with the rest
> of the configuration, or checks hacked out if people think they're
> getting in the way without realising what they're there for.

Maybe a big fat warning comment in the code ? Apart from that, I agree,
I don't think we can do much.

-- 
Regards,

Laurent Pinchart

  reply	other threads:[~2021-11-29 19:16 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-25 16:53 [PATCH v6 00/15] Add support for X86/ACPI camera sensor/PMIC setup with clk and regulator platform data Hans de Goede
2021-11-25 16:53 ` [PATCH v6 01/15] ACPI: delay enumeration of devices with a _DEP pointing to an INT3472 device Hans de Goede
2021-11-25 16:53 ` [PATCH v6 02/15] i2c: acpi: Use acpi_dev_ready_for_enumeration() helper Hans de Goede
2021-11-26  7:16   ` Mika Westerberg
2021-11-25 16:54 ` [PATCH v6 03/15] i2c: acpi: Add i2c_acpi_new_device_by_fwnode() function Hans de Goede
2021-11-25 17:22   ` Andy Shevchenko
2021-11-26 11:19     ` Hans de Goede
2021-11-26  7:18   ` Mika Westerberg
2021-11-27 22:49   ` Wolfram Sang
2021-11-25 16:54 ` [PATCH v6 04/15] platform_data: Add linux/platform_data/tps68470.h file Hans de Goede
2021-11-25 16:54 ` [PATCH v6 05/15] regulator: Introduce tps68470-regulator driver Hans de Goede
2021-11-25 23:32   ` Laurent Pinchart
2021-11-26 11:22     ` Hans de Goede
2021-11-27 23:38       ` Laurent Pinchart
2021-11-29 12:08         ` Mark Brown
2021-11-29 15:35           ` Laurent Pinchart [this message]
2021-11-25 16:54 ` [PATCH v6 06/15] clk: Introduce clk-tps68470 driver Hans de Goede
2021-11-25 16:54 ` [PATCH v6 07/15] platform/x86: int3472: Enable I2c daisy chain Hans de Goede
2021-11-25 23:39   ` Laurent Pinchart
2021-11-26 11:30     ` Hans de Goede
2021-11-26 11:39       ` Daniel Scally
2021-11-26 11:45         ` Hans de Goede
2021-11-26 11:56           ` Daniel Scally
2021-12-03 10:21           ` Hans de Goede
2021-11-25 16:54 ` [PATCH v6 08/15] platform/x86: int3472: Split into 2 drivers Hans de Goede
2021-11-25 16:54 ` [PATCH v6 09/15] platform/x86: int3472: Add get_sensor_adev_and_name() helper Hans de Goede
2021-11-25 16:54 ` [PATCH v6 10/15] platform/x86: int3472: Pass tps68470_clk_platform_data to the tps68470-regulator MFD-cell Hans de Goede
2021-11-25 16:54 ` [PATCH v6 11/15] platform/x86: int3472: Pass tps68470_regulator_platform_data " Hans de Goede
2021-11-25 16:54 ` [PATCH v6 12/15] platform/x86: int3472: Deal with probe ordering issues Hans de Goede
2021-11-25 16:54 ` [PATCH v6 13/15] media: ipu3-cio2: Defer probing until the PMIC is fully setup Hans de Goede
2021-11-25 16:54 ` [PATCH v6 14/15] media: ipu3-cio2: Call cio2_bridge_init() before anything else Hans de Goede
2021-11-25 16:54 ` [PATCH v6 15/15] media: ipu3-cio2: Add support for instantiating i2c-clients for VCMs Hans de Goede

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