linux-kernel - Re: [PATCH] i2c: mt65xx: allow optional pmic clock

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Message-ID: <ZQLNWHKlIZNd7x4l@makrotopia.org>
Date:   Thu, 14 Sep 2023 10:07:36 +0100
From:   Daniel Golle <daniel@...rotopia.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     Qii Wang <qii.wang@...iatek.com>,
        Andi Shyti <andi.shyti@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        郭小桥 <joe@...nstrong.cn>
Subject: Re: [PATCH] i2c: mt65xx: allow optional pmic clock

On Wed, Sep 13, 2023 at 04:00:53PM +0200, AngeloGioacchino Del Regno wrote:
> Il 27/08/23 04:13, Daniel Golle ha scritto:
> > Using the I2C host controller on the MT7981 SoC requires 4 clocks to
> > be enabled. One of them, the pmic clk, is only enabled in case
> > 'mediatek,have-pmic' is also set which has other consequences which
> > are not desired in this case.
> > 
> > Allow defining a pmic clk even in case the 'mediatek,have-pmic' propterty
> > is not present and the bus is not used to connect to a pmic, but may
> > still require to enable the pmic clock.
> > 
> > Signed-off-by: Daniel Golle <daniel@...rotopia.org>
> > ---
> >   drivers/i2c/busses/i2c-mt65xx.c | 12 ++++++++----
> >   1 file changed, 8 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
> > index 1a9b5a068ef1b..a8b5719c33729 100644
> > --- a/drivers/i2c/busses/i2c-mt65xx.c
> > +++ b/drivers/i2c/busses/i2c-mt65xx.c
> > @@ -1442,15 +1442,19 @@ static int mtk_i2c_probe(struct platform_device *pdev)
> >   	if (IS_ERR(i2c->clocks[I2C_MT65XX_CLK_ARB].clk))
> >   		return PTR_ERR(i2c->clocks[I2C_MT65XX_CLK_ARB].clk);
> > +	i2c->clocks[I2C_MT65XX_CLK_PMIC].clk = devm_clk_get_optional(&pdev->dev, "pmic");
> > +	if (IS_ERR(i2c->clocks[I2C_MT65XX_CLK_PMIC].clk)) {
> > +		dev_err(&pdev->dev, "cannot get pmic clock\n");
> > +		return PTR_ERR(i2c->clocks[I2C_MT65XX_CLK_PMIC].clk);
> > +	}
> > +
> >   	if (i2c->have_pmic) {
> 
> ...but you're not changing speed_clk if !i2c->have_pmic, I'm not sure that
> this will work correctly. Perhaps you wanted to also set speed_clk if the
> clock is present?

No, if I wanted that I could have used the existing 'mediatek,have-pmic'
property -- however, all needed e.g. on MT7981 is to make sure the
clock is enabled, but still use I2C_MT65XX_CLK_MAIN as speed_clk.

> 
> if (IS_ERR...) {
> 	error handling
> } else if (clk is present)
> 	speed_clk = I2C_MT65XX_CLK_PMIC;
> 
> if (have_pmic && !clk_is_present)
> 	error
> 
> Regards,
> Angelo
> 
> > -		i2c->clocks[I2C_MT65XX_CLK_PMIC].clk = devm_clk_get(&pdev->dev, "pmic");
> > -		if (IS_ERR(i2c->clocks[I2C_MT65XX_CLK_PMIC].clk)) {
> > +		if (!i2c->clocks[I2C_MT65XX_CLK_PMIC].clk) {
> >   			dev_err(&pdev->dev, "cannot get pmic clock\n");
> > -			return PTR_ERR(i2c->clocks[I2C_MT65XX_CLK_PMIC].clk);
> > +			return -ENODEV;
> >   		}
> >   		speed_clk = I2C_MT65XX_CLK_PMIC;
> >   	} else {
> > -		i2c->clocks[I2C_MT65XX_CLK_PMIC].clk = NULL;
> >   		speed_clk = I2C_MT65XX_CLK_MAIN;
> >   	}
> 
>