linux-kernel - Re: [PATCH 1/3] phy: rockchip-emmc: Allow to set drive impedance via DTS.

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Date:   Fri, 1 Mar 2019 17:21:36 +0100
From:   Christoph Müllner 
        <christoph.muellner@...obroma-systems.com>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     robh+dt@...nel.org, mark.rutland@....com, shawn.lin@...k-chips.com,
        Philipp Tomsich <philipp.tomsich@...obroma-systems.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Klaus Goger <klaus.goger@...obroma-systems.com>,
        Douglas Anderson <dianders@...omium.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Matthias Brugger <mbrugger@...e.com>,
        Emil Renner Berthing <kernel@...il.dk>,
        Tony Xie <tony.xie@...k-chips.com>,
        Randy Li <ayaka@...lik.info>,
        Vicente Bergas <vicencb@...il.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] phy: rockchip-emmc: Allow to set drive impedance via
 DTS.

Hi Heiko,

> On 01.03.2019, at 16:59, Heiko Stuebner <heiko@...ech.de> wrote:
> 
> Hi Christoph,
> 
> Am Freitag, 1. März 2019, 16:33:43 CET schrieb Christoph Muellner:
>> The rockchip-emmc PHY can be configured with different
>> drive impedance values. Currenlty a value of 50 Ohm is
>> hard coded into the driver.
>> 
>> This patch introduces the DTS property 'drive-impedance-ohm'
>> for the rockchip-emmc phy node, which uses the value from the DTS
>> to setup the drive impedance accordingly.
>> 
>> Signed-off-by: Christoph Muellner <christoph.muellner@...obroma-systems.com>
>> Signed-off-by: Philipp Tomsich <philipp.tomsich@...obroma-systems.com>
>> ---
>> drivers/phy/rockchip/phy-rockchip-emmc.c | 38 ++++++++++++++++++++++++++++++--
> 
> looks good on first glance, but is missing an addition to the emmc-phy
> devicetree binding in
> 	Documentation/devicetree/bindings/phy/rockchip-emmc-phy.txt

you are right.
I've just sent that in a separate patch (DT doc changes need to be in a separate commit anyways).

Thanks,
Christoph

> 
> 
> Heiko
> 
>> 1 file changed, 36 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/phy/rockchip/phy-rockchip-emmc.c b/drivers/phy/rockchip/phy-rockchip-emmc.c
>> index 19bf84f0bc67..5413fa73dd45 100644
>> --- a/drivers/phy/rockchip/phy-rockchip-emmc.c
>> +++ b/drivers/phy/rockchip/phy-rockchip-emmc.c
>> @@ -87,6 +87,7 @@ struct rockchip_emmc_phy {
>> 	unsigned int	reg_offset;
>> 	struct regmap	*reg_base;
>> 	struct clk	*emmcclk;
>> +	unsigned int drive_impedance;
>> };
>> 
>> static int rockchip_emmc_phy_power(struct phy *phy, bool on_off)
>> @@ -281,10 +282,10 @@ static int rockchip_emmc_phy_power_on(struct phy *phy)
>> {
>> 	struct rockchip_emmc_phy *rk_phy = phy_get_drvdata(phy);
>> 
>> -	/* Drive impedance: 50 Ohm */
>> +	/* Drive impedance: from DTS */
>> 	regmap_write(rk_phy->reg_base,
>> 		     rk_phy->reg_offset + GRF_EMMCPHY_CON6,
>> -		     HIWORD_UPDATE(PHYCTRL_DR_50OHM,
>> +		     HIWORD_UPDATE(rk_phy->drive_impedance,
>> 				   PHYCTRL_DR_MASK,
>> 				   PHYCTRL_DR_SHIFT));
>> 
>> @@ -314,6 +315,28 @@ static const struct phy_ops ops = {
>> 	.owner		= THIS_MODULE,
>> };
>> 
>> +static u32 convert_drive_impedance_ohm(struct platform_device *pdev, u32 dr_ohm)
>> +{
>> +	switch (dr_ohm) {
>> +	case 100:
>> +		return PHYCTRL_DR_100OHM;
>> +	case 66:
>> +		return PHYCTRL_DR_66OHM;
>> +	case 50:
>> +		return PHYCTRL_DR_50OHM;
>> +	case 40:
>> +		return PHYCTRL_DR_40OHM;
>> +	case 33:
>> +		return PHYCTRL_DR_33OHM;
>> +	}
>> +
>> +	dev_warn(&pdev->dev,
>> +		"Invalid value %u for drive-impedance-ohm. "
>> +		"Falling back to 50 Ohm.\n",
>> +		dr_ohm);
>> +	return PHYCTRL_DR_50OHM;
>> +}
>> +
>> static int rockchip_emmc_phy_probe(struct platform_device *pdev)
>> {
>> 	struct device *dev = &pdev->dev;
>> @@ -322,6 +345,7 @@ static int rockchip_emmc_phy_probe(struct platform_device *pdev)
>> 	struct phy_provider *phy_provider;
>> 	struct regmap *grf;
>> 	unsigned int reg_offset;
>> +	u32 val;
>> 
>> 	if (!dev->parent || !dev->parent->of_node)
>> 		return -ENODEV;
>> @@ -345,6 +369,16 @@ static int rockchip_emmc_phy_probe(struct platform_device *pdev)
>> 	rk_phy->reg_offset = reg_offset;
>> 	rk_phy->reg_base = grf;
>> 
>> +	if (of_property_read_u32(dev->of_node, "drive-impedance-ohm", &val)) {
>> +		dev_info(dev,
>> +			"Missing drive-impedance-ohm property in node %s "
>> +			"Falling back to 50 Ohm.\n",
>> +			dev->of_node->name);
>> +		rk_phy->drive_impedance = PHYCTRL_DR_50OHM;
>> +	} else {
>> +		rk_phy->drive_impedance = convert_drive_impedance_ohm(pdev, val);
>> +	}
>> +
>> 	generic_phy = devm_phy_create(dev, dev->of_node, &ops);
>> 	if (IS_ERR(generic_phy)) {
>> 		dev_err(dev, "failed to create PHY\n");
>> 
> 
> 
> 
>