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Date:   Tue, 31 May 2022 08:47:18 -0500
From:   Patrick Williams <patrick@stwcx.xyz>
To:     Potin Lai <potin.lai.pt@gmail.com>
Cc:     Brendan Higgins <brendanhiggins@google.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Joel Stanley <joel@jms.id.au>,
        Andrew Jeffery <andrew@aj.id.au>,
        Porin Lai <potin.lai@quantatw.com>, linux-i2c@vger.kernel.org,
        openbmc@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org,
        linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] aspeed: i2c: add manual clock setup feature
Message-ID: <YpYcZn+Zsz3g7xl+@heinlein.stwcx.org.github.beta.tailscale.net>
References: <20220530114056.8722-1-potin.lai.pt@gmail.com>
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On Mon, May 30, 2022 at 07:40:56PM +0800, Potin Lai wrote:
> From: Porin Lai <potin.lai.pt@gmail.com>
>=20
> Add properties for manual tuning i2c clock timing register.
>=20
> * aspeed,i2c-manual-clk: Enable aspeed i2c clock manual setup
> * aspeed,i2c-base-clk-div: Base Clock divisor (tBaseClk)
> * aspeed,i2c-clk-high-cycle: Cycles of clock-high pulse (tClkHigh)
> * aspeed,i2c-clk-low-cycle: Cycles of clock-low pulse (tClkLow)

Do we need to add these to
Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml ?

>=20
> Signed-off-by: Potin Lai <potin.lai.pt@gmail.com>
> ---
>  drivers/i2c/busses/i2c-aspeed.c | 55 ++++++++++++++++++++++++++++++++-
>  1 file changed, 54 insertions(+), 1 deletion(-)
>=20
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-asp=
eed.c
> index 67e8b97c0c95..1f4b5c4b5bf4 100644
> --- a/drivers/i2c/busses/i2c-aspeed.c
> +++ b/drivers/i2c/busses/i2c-aspeed.c
> @@ -898,6 +898,56 @@ static int aspeed_i2c_init_clk(struct aspeed_i2c_bus=
 *bus)
>  	return 0;
>  }
> =20
> +/* precondition: bus.lock has been acquired. */
> +static int aspeed_i2c_manual_clk_setup(struct aspeed_i2c_bus *bus)
> +{
> +	u32 divisor, clk_high, clk_low, clk_reg_val;
> +
> +	if (device_property_read_u32(bus->dev, "aspeed,i2c-base-clk-div",
> +				     &divisor) !=3D 0) {
> +		dev_err(bus->dev, "Could not read aspeed,i2c-base-clk-div\n");
> +		return -EINVAL;
> +	} else if (divisor > ASPEED_I2CD_TIME_BASE_DIVISOR_MASK) {
> +		dev_err(bus->dev, "Invalid aspeed,i2c-base-clk-div: %u\n",
> +			divisor);
> +		return -EINVAL;
> +	}
> +
> +	if (device_property_read_u32(bus->dev, "aspeed,i2c-clk-high-cycle",
> +				     &clk_high) !=3D 0) {
> +		dev_err(bus->dev, "Could not read aspeed,i2c-clk-high-cycle\n");
> +		return -EINVAL;
> +	} else if (clk_high > ASPEED_I2CD_TIME_SCL_REG_MAX) {
> +		dev_err(bus->dev, "Invalid aspeed,i2c-clk-high-cycle: %u\n",
> +			clk_high);
> +		return -EINVAL;
> +	}
> +
> +	if (device_property_read_u32(bus->dev, "aspeed,i2c-clk-low-cycle",
> +				     &clk_low) !=3D 0) {
> +		dev_err(bus->dev, "Could not read aspeed,i2c-clk-low-cycle\n");
> +		return -EINVAL;
> +	} else if (clk_low > ASPEED_I2CD_TIME_SCL_REG_MAX) {
> +		dev_err(bus->dev, "Invalid aspeed,i2c-clk-low-cycle: %u\n",
> +			clk_low);
> +		return -EINVAL;
> +	}
> +
> +	clk_reg_val =3D readl(bus->base + ASPEED_I2C_AC_TIMING_REG1);
> +	clk_reg_val &=3D (ASPEED_I2CD_TIME_TBUF_MASK |
> +			ASPEED_I2CD_TIME_THDSTA_MASK |
> +			ASPEED_I2CD_TIME_TACST_MASK);
> +	clk_reg_val |=3D (divisor & ASPEED_I2CD_TIME_BASE_DIVISOR_MASK)
> +			| ((clk_high << ASPEED_I2CD_TIME_SCL_HIGH_SHIFT)
> +			   & ASPEED_I2CD_TIME_SCL_HIGH_MASK)
> +			| ((clk_low << ASPEED_I2CD_TIME_SCL_LOW_SHIFT)
> +			   & ASPEED_I2CD_TIME_SCL_LOW_MASK);
> +	writel(clk_reg_val, bus->base + ASPEED_I2C_AC_TIMING_REG1);
> +	writel(ASPEED_NO_TIMEOUT_CTRL, bus->base + ASPEED_I2C_AC_TIMING_REG2);
> +
> +	return 0;
> +}
> +
>  /* precondition: bus.lock has been acquired. */
>  static int aspeed_i2c_init(struct aspeed_i2c_bus *bus,
>  			     struct platform_device *pdev)
> @@ -908,7 +958,10 @@ static int aspeed_i2c_init(struct aspeed_i2c_bus *bu=
s,
>  	/* Disable everything. */
>  	writel(0, bus->base + ASPEED_I2C_FUN_CTRL_REG);
> =20
> -	ret =3D aspeed_i2c_init_clk(bus);
> +	if (of_property_read_bool(pdev->dev.of_node, "aspeed,i2c-manual-clk"))
> +		ret =3D aspeed_i2c_manual_clk_setup(bus);
> +	else
> +		ret =3D aspeed_i2c_init_clk(bus);
>  	if (ret < 0)
>  		return ret;
> =20
> --=20
> 2.17.1
>=20

--=20
Patrick Williams

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