linux-kernel - Re: [PATCH v15 2/3] i2c: aspeed: support AST2600 i2c new register mode driver

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Message-ID: <6d8a0d8916e185090423d42217262450ee948088.camel@pengutronix.de>
Date: Wed, 13 Nov 2024 11:03:52 +0100
From: Philipp Zabel <p.zabel@...gutronix.de>
To: Ryan Chen <ryan_chen@...eedtech.com>, "brendan.higgins@...ux.dev"
	 <brendan.higgins@...ux.dev>, "benh@...nel.crashing.org"
	 <benh@...nel.crashing.org>, "joel@....id.au" <joel@....id.au>, 
	"andi.shyti@...nel.org"
	 <andi.shyti@...nel.org>, "robh@...nel.org" <robh@...nel.org>, 
	"krzk+dt@...nel.org"
	 <krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>, 
	"andrew@...econstruct.com.au"
	 <andrew@...econstruct.com.au>, "andriy.shevchenko@...ux.intel.com"
	 <andriy.shevchenko@...ux.intel.com>, "linux-i2c@...r.kernel.org"
	 <linux-i2c@...r.kernel.org>, "openbmc@...ts.ozlabs.org"
	 <openbmc@...ts.ozlabs.org>, "devicetree@...r.kernel.org"
	 <devicetree@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org"
	 <linux-arm-kernel@...ts.infradead.org>, "linux-aspeed@...ts.ozlabs.org"
	 <linux-aspeed@...ts.ozlabs.org>, "linux-kernel@...r.kernel.org"
	 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v15 2/3] i2c: aspeed: support AST2600 i2c new register
 mode driver

On Mi, 2024-11-13 at 07:43 +0000, Ryan Chen wrote:
> > Subject: Re: [PATCH v15 2/3] i2c: aspeed: support AST2600 i2c new
> > register
> > mode driver
> > 
> > On Mo, 2024-10-07 at 11:52 +0800, Ryan Chen wrote:
> > > Add i2c new register mode driver to support AST2600 i2c new
> > > register
> > > mode. AST2600 i2c controller have legacy and new register mode.
> > > The
> > > new register mode have global register support 4 base clock for
> > > scl
> > > clock selection, and new clock divider mode. The new register
> > > mode
> > > have separate register set to control i2c controller and target.
> > > This
> > > patch is for i2c controller mode driver.
> > > 
> > > Signed-off-by: Ryan Chen <ryan_chen@...eedtech.com>
> > > ---
> > >  drivers/i2c/busses/Kconfig       |   11 +
> > >  drivers/i2c/busses/Makefile      |    1 +
> > >  drivers/i2c/busses/i2c-ast2600.c | 1032
> > > ++++++++++++++++++++++++++++++
> > >  3 files changed, 1044 insertions(+)
> > >  create mode 100644 drivers/i2c/busses/i2c-ast2600.c
> > > 
> > [...]
> > > diff --git a/drivers/i2c/busses/i2c-ast2600.c
> > > b/drivers/i2c/busses/i2c-ast2600.c
> > > new file mode 100644
> > > index 000000000000..17ba0ee77c27
> > > --- /dev/null
> > > +++ b/drivers/i2c/busses/i2c-ast2600.c
> > > @@ -0,0 +1,1032 @@
> > [...]
> > > +static int ast2600_i2c_probe(struct platform_device *pdev) {
> > [...]
> > > +	i2c_bus->rst = devm_reset_control_get_shared(dev, NULL);
> > > +	if (IS_ERR(i2c_bus->rst))
> > > +		return dev_err_probe(dev, PTR_ERR(i2c_bus->rst),
> > > "Missing reset
> > > +ctrl\n");
> > > +
> > > +	reset_control_deassert(i2c_bus->rst);
> > 
> > The shared reset should be asserted again in ast2600_i2c_remove().
> > 
> Hello,
> It is share reset, if unbond driver and asserted the reset, it will
> affect others driver running (which is share with the same reset.)

Shared reset_control_deassert/assert are refcounted, like
clk_enable/disable, see [1]. The reset line will only be asserted when
the last driver calls reset_control_assert.

[1] https://docs.kernel.org/driver-api/reset.html#shared-and-exclusive-resets

regards
Philipp