From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH 1/3] phy: rockchip-emmc: Allow to set drive impedance via DTS. Date: Fri, 1 Mar 2019 16:51:11 +0000 Message-ID: <1347b956-5682-1f86-b38c-7768bb9ffd23@arm.com> References: <20190301153348.29870-1-christoph.muellner@theobroma-systems.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190301153348.29870-1-christoph.muellner@theobroma-systems.com> Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org To: Christoph Muellner , robh+dt@kernel.org, mark.rutland@arm.com, heiko@sntech.de, shawn.lin@rock-chips.com Cc: devicetree@vger.kernel.org, Matthias Brugger , linux-kernel@vger.kernel.org, Emil Renner Berthing , Viresh Kumar , Randy Li , Douglas Anderson , Vicente Bergas , Kishon Vijay Abraham I , linux-rockchip@lists.infradead.org, Tony Xie , Klaus Goger , Enric Balletbo i Serra , Philipp Tomsich , Ezequiel Garcia , linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org On 01/03/2019 15:33, Christoph Muellner wrote: > 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 > Signed-off-by: Philipp Tomsich > --- > drivers/phy/rockchip/phy-rockchip-emmc.c | 38 ++++++++++++++++++++++++++++++-- > 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); I think we're aiming to use %pOF for node names now, but here it looks redundant anyway - dev_info() will already show the device name, which for an of_platform device is the same thing. > + rk_phy->drive_impedance = PHYCTRL_DR_50OHM; > + } else { > + rk_phy->drive_impedance = convert_drive_impedance_ohm(pdev, val); > + } FWIW, if you initialise val to the default (i.e. 50) then you could get rid of the "else" case and just do the conversion unconditionally. That's a fairly common idiom for reading optional properties. Robin. > + > generic_phy = devm_phy_create(dev, dev->of_node, &ops); > if (IS_ERR(generic_phy)) { > dev_err(dev, "failed to create PHY\n"); >