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

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Message-ID:
 <OS8PR06MB75412A3FB0FD82174DD1C7D9F2242@OS8PR06MB7541.apcprd06.prod.outlook.com>
Date: Fri, 15 Nov 2024 00:18:27 +0000
From: Ryan Chen <ryan_chen@...eedtech.com>
To: Philipp Zabel <p.zabel@...gutronix.de>, "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

> 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
> 
Thanks a lot, I will add in next version submit.

> regards
> Philipp