Message ID | 3a8baa278457c62f24504ab817b7ba5431391394.1689160067.git.quic_varada@quicinc.com |
---|---|
State | New |
Headers | show |
Series | Enable IPQ5332 USB2 | expand |
On 12-07-23, 17:08, Varadarajan Narayanan wrote: > Add the M31 USB2 phy driver. > > Signed-off-by: Varadarajan Narayanan <quic_varada@quicinc.com> > --- > v4: > Remove unused enum > Error handling for devm_clk_get > v1: > Combine driver, makefile and kconfig into 1 patch > Remove 'qscratch' region and its usage. The controller driver takes care > of those settings > Use compatible/data to handle ipq5332 init > Drop the default case > Get resources by index instead of name as there is only one resource > Add clock > Fix review comments in the driver > --- > drivers/phy/qualcomm/Kconfig | 11 ++ > drivers/phy/qualcomm/Makefile | 1 + > drivers/phy/qualcomm/phy-qcom-m31.c | 256 ++++++++++++++++++++++++++++++++++++ > 3 files changed, 268 insertions(+) > create mode 100644 drivers/phy/qualcomm/phy-qcom-m31.c > > diff --git a/drivers/phy/qualcomm/Kconfig b/drivers/phy/qualcomm/Kconfig > index 97ca595..76be191 100644 > --- a/drivers/phy/qualcomm/Kconfig > +++ b/drivers/phy/qualcomm/Kconfig > @@ -197,3 +197,14 @@ config PHY_QCOM_SGMII_ETH > help > Enable this to support the internal SerDes/SGMII PHY on various > Qualcomm chipsets. > + > +config PHY_QCOM_M31_USB Sorted alphabetically please > + tristate "Qualcomm M31 HS PHY driver support" > + depends on (USB || USB_GADGET) && ARCH_QCOM > + select USB_PHY > + help > + Enable this to support M31 HS PHY transceivers on Qualcomm chips > + with DWC3 USB core. It handles PHY initialization, clock > + management required after resetting the hardware and power > + management. This driver is required even for peripheral only or > + host only mode configurations. > diff --git a/drivers/phy/qualcomm/Makefile b/drivers/phy/qualcomm/Makefile > index b030858..0b5dd66 100644 > --- a/drivers/phy/qualcomm/Makefile > +++ b/drivers/phy/qualcomm/Makefile > @@ -22,3 +22,4 @@ obj-$(CONFIG_PHY_QCOM_USB_SS) += phy-qcom-usb-ss.o > obj-$(CONFIG_PHY_QCOM_USB_SNPS_FEMTO_V2)+= phy-qcom-snps-femto-v2.o > obj-$(CONFIG_PHY_QCOM_IPQ806X_USB) += phy-qcom-ipq806x-usb.o > obj-$(CONFIG_PHY_QCOM_SGMII_ETH) += phy-qcom-sgmii-eth.o > +obj-$(CONFIG_PHY_QCOM_M31_USB) += phy-qcom-m31.o this one too > diff --git a/drivers/phy/qualcomm/phy-qcom-m31.c b/drivers/phy/qualcomm/phy-qcom-m31.c > new file mode 100644 > index 0000000..fd568ef > --- /dev/null > +++ b/drivers/phy/qualcomm/phy-qcom-m31.c > @@ -0,0 +1,256 @@ > +// SPDX-License-Identifier: GPL-2.0+ > +/* > + * Copyright (c) 2014-2016, 2020, The Linux Foundation. All rights reserved. > + */ we are in 2023 > + > +#include <linux/clk.h> > +#include <linux/delay.h> > +#include <linux/err.h> > +#include <linux/io.h> > +#include <linux/kernel.h> > +#include <linux/module.h> > +#include <linux/of_device.h> > +#include <linux/of.h> > +#include <linux/platform_device.h> > +#include <linux/reset.h> > +#include <linux/slab.h> > +#include <linux/usb/of.h> > +#include <linux/usb/phy.h> > + > +#define USB2PHY_PORT_UTMI_CTRL1 0x40 > + > +#define USB2PHY_PORT_UTMI_CTRL2 0x44 > + #define UTMI_ULPI_SEL BIT(7) > + #define UTMI_TEST_MUX_SEL BIT(6) > + > +#define HS_PHY_CTRL_REG 0x10 > + #define UTMI_OTG_VBUS_VALID BIT(20) > + #define SW_SESSVLD_SEL BIT(28) > + > +#define USB_PHY_UTMI_CTRL0 0x3c > + > +#define USB_PHY_UTMI_CTRL5 0x50 > + #define POR_EN BIT(1) > + #define ATERESET ~BIT(0) ?? > + > +#define USB_PHY_HS_PHY_CTRL_COMMON0 0x54 > + #define COMMONONN BIT(7) > + #define FSEL BIT(4) > + #define RETENABLEN BIT(3) > + #define FREQ_24MHZ (5 << 4) Use GENMASK for these > + > +#define USB_PHY_HS_PHY_CTRL2 0x64 > + #define USB2_SUSPEND_N_SEL BIT(3) > + #define USB2_SUSPEND_N BIT(2) > + #define USB2_UTMI_CLK_EN BIT(1) > + > +#define USB_PHY_CFG0 0x94 > + #define UTMI_PHY_OVERRIDE_EN BIT(1) > + > +#define USB_PHY_REFCLK_CTRL 0xa0 > + #define CLKCORE BIT(1) > + > +#define USB2PHY_PORT_POWERDOWN 0xa4 > + #define POWER_UP BIT(0) > + #define POWER_DOWN 0 > + > +#define USB_PHY_FSEL_SEL 0xb8 > + #define FREQ_SEL BIT(0) > + > +#define USB2PHY_USB_PHY_M31_XCFGI_1 0xbc > + #define USB2_0_TX_ENABLE BIT(2) > + > +#define USB2PHY_USB_PHY_M31_XCFGI_4 0xc8 > + #define HSTX_SLEW_RATE_565PS GENMASK(1, 0) > + #define PLL_CHARGING_PUMP_CURRENT_35UA GENMASK(4, 3) > + #define ODT_VALUE_38_02_OHM GENMASK(7, 6) > + > +#define USB2PHY_USB_PHY_M31_XCFGI_5 0xcc > + #define ODT_VALUE_45_02_OHM BIT(2) > + #define HSTX_PRE_EMPHASIS_LEVEL_0_55MA BIT(0) > + > +#define USB2PHY_USB_PHY_M31_XCFGI_11 0xe4 > + #define XCFG_COARSE_TUNE_NUM BIT(1) > + #define XCFG_FINE_TUNE_NUM BIT(3) > + > +struct m31_phy_regs { > + u32 off; > + u32 val; > + u32 delay; > +}; > + > +struct m31_priv_data { > + bool ulpi_mode; > + const struct m31_phy_regs *regs; > +}; > + > +#define M31_REG(__o, __v, __d) \ > + { .off = __o, .val = __v, .delay = __d } > + > +#define M31_REG_INVALID 0xffffffffu > + > +struct m31_phy_regs m31_ipq5332_regs[] = { > + M31_REG(USB_PHY_CFG0, UTMI_PHY_OVERRIDE_EN, 0), > + M31_REG(USB_PHY_UTMI_CTRL5, POR_EN, 15), > + M31_REG(USB_PHY_FSEL_SEL, FREQ_SEL, 0), > + M31_REG(USB_PHY_HS_PHY_CTRL_COMMON0, > + COMMONONN | FREQ_24MHZ | RETENABLEN, 0), > + M31_REG(USB_PHY_UTMI_CTRL5, POR_EN & ATERESET, 0), > + M31_REG(USB_PHY_HS_PHY_CTRL2, > + USB2_SUSPEND_N_SEL | USB2_SUSPEND_N | USB2_UTMI_CLK_EN, 0), > + M31_REG(USB2PHY_USB_PHY_M31_XCFGI_11, > + XCFG_COARSE_TUNE_NUM | XCFG_FINE_TUNE_NUM, 0), > + M31_REG(USB2PHY_USB_PHY_M31_XCFGI_4, > + HSTX_SLEW_RATE_565PS | PLL_CHARGING_PUMP_CURRENT_35UA | > + ODT_VALUE_38_02_OHM, 0), > + M31_REG(USB2PHY_USB_PHY_M31_XCFGI_1, USB2_0_TX_ENABLE, 0), > + M31_REG(USB2PHY_USB_PHY_M31_XCFGI_5, > + ODT_VALUE_45_02_OHM | HSTX_PRE_EMPHASIS_LEVEL_0_55MA, 4), > + M31_REG(USB_PHY_UTMI_CTRL5, 0x0, 0), > + M31_REG(USB_PHY_HS_PHY_CTRL2, USB2_SUSPEND_N | USB2_UTMI_CLK_EN, 0), > + M31_REG(M31_REG_INVALID, 0, 0), > +}; > + > +struct m31usb_phy { > + struct usb_phy phy; > + void __iomem *base; > + const struct m31_phy_regs *regs; > + > + struct clk *cfg_ahb_clk; > + struct reset_control *phy_reset; > + > + bool cable_connected; > + bool suspended; > + bool ulpi_mode; > +}; > + > +static void m31usb_phy_enable_clock(struct m31usb_phy *qphy) > +{ > + const struct m31_phy_regs *regs = qphy->regs; > + > + for (; regs->off != M31_REG_INVALID; regs++) { why have last entry as invalid and check that, this is an array so you can use ARRAY_SIZE to define the count of regs > + writel(regs->val, qphy->base + regs->off); > + if (regs->delay) > + udelay(regs->delay); > + } > +} > + > +static int m31usb_phy_init(struct usb_phy *phy) > +{ > + int ret; > + struct m31usb_phy *qphy = container_of(phy, struct m31usb_phy, phy); > + > + ret = clk_prepare_enable(qphy->cfg_ahb_clk); > + if (ret) { > + dev_err(phy->dev, "failed to enable cfg ahb clock, %d\n", ret); > + return ret; > + } > + > + /* Perform phy reset */ > + reset_control_assert(qphy->phy_reset); > + udelay(5); > + reset_control_deassert(qphy->phy_reset); > + > + /* configure for ULPI mode if requested */ > + if (qphy->ulpi_mode) > + writel(0x0, qphy->base + USB2PHY_PORT_UTMI_CTRL2); > + > + /* Enable the PHY */ > + writel(POWER_UP, qphy->base + USB2PHY_PORT_POWERDOWN); > + > + /* Make sure above write completed */ > + wmb(); > + > + /* Turn on phy ref clock */ > + m31usb_phy_enable_clock(qphy); > + > + return 0; > +} > + > +static void m31usb_phy_shutdown(struct usb_phy *phy) > +{ > + struct m31usb_phy *qphy = container_of(phy, struct m31usb_phy, phy); > + > + /* Disable the PHY */ > + writel_relaxed(POWER_DOWN, qphy->base + USB2PHY_PORT_POWERDOWN); > + /* Make sure above write completed */ > + wmb(); > + > + clk_disable_unprepare(qphy->cfg_ahb_clk); > +} > + > +static int m31usb_phy_probe(struct platform_device *pdev) > +{ > + const struct m31_priv_data *data; > + struct device *dev = &pdev->dev; > + struct m31usb_phy *qphy; > + int ret; > + > + qphy = devm_kzalloc(dev, sizeof(*qphy), GFP_KERNEL); > + if (!qphy) > + return -ENOMEM; > + > + qphy->phy.dev = dev; > + > + qphy->base = devm_platform_ioremap_resource(pdev, 0); > + if (IS_ERR(qphy->base)) > + return PTR_ERR(qphy->base); > + > + qphy->phy_reset = devm_reset_control_get_exclusive_by_index(dev, 0); > + if (IS_ERR(qphy->phy_reset)) > + return PTR_ERR(qphy->phy_reset); > + > + qphy->cfg_ahb_clk = devm_clk_get(dev, "cfg_ahb"); > + if (IS_ERR(qphy->cfg_ahb_clk)) { > + ret = PTR_ERR(qphy->cfg_ahb_clk); > + dev_err(dev, "failed to get cfg_ahb clock, %d\n", ret); > + return ret; > + } > + > + platform_set_drvdata(pdev, qphy); > + > + data = of_device_get_match_data(dev); > + qphy->regs = data->regs; > + qphy->ulpi_mode = data->ulpi_mode; > + > + qphy->phy.label = "m31-usb-phy"; > + qphy->phy.init = m31usb_phy_init; > + qphy->phy.shutdown = m31usb_phy_shutdown; > + qphy->phy.type = USB_PHY_TYPE_USB2; > + > + ret = usb_add_phy_dev(&qphy->phy); why usb and not devm_phy_create()? It should be generic phy here
diff --git a/drivers/phy/qualcomm/Kconfig b/drivers/phy/qualcomm/Kconfig index 97ca595..76be191 100644 --- a/drivers/phy/qualcomm/Kconfig +++ b/drivers/phy/qualcomm/Kconfig @@ -197,3 +197,14 @@ config PHY_QCOM_SGMII_ETH help Enable this to support the internal SerDes/SGMII PHY on various Qualcomm chipsets. + +config PHY_QCOM_M31_USB + tristate "Qualcomm M31 HS PHY driver support" + depends on (USB || USB_GADGET) && ARCH_QCOM + select USB_PHY + help + Enable this to support M31 HS PHY transceivers on Qualcomm chips + with DWC3 USB core. It handles PHY initialization, clock + management required after resetting the hardware and power + management. This driver is required even for peripheral only or + host only mode configurations. diff --git a/drivers/phy/qualcomm/Makefile b/drivers/phy/qualcomm/Makefile index b030858..0b5dd66 100644 --- a/drivers/phy/qualcomm/Makefile +++ b/drivers/phy/qualcomm/Makefile @@ -22,3 +22,4 @@ obj-$(CONFIG_PHY_QCOM_USB_SS) += phy-qcom-usb-ss.o obj-$(CONFIG_PHY_QCOM_USB_SNPS_FEMTO_V2)+= phy-qcom-snps-femto-v2.o obj-$(CONFIG_PHY_QCOM_IPQ806X_USB) += phy-qcom-ipq806x-usb.o obj-$(CONFIG_PHY_QCOM_SGMII_ETH) += phy-qcom-sgmii-eth.o +obj-$(CONFIG_PHY_QCOM_M31_USB) += phy-qcom-m31.o diff --git a/drivers/phy/qualcomm/phy-qcom-m31.c b/drivers/phy/qualcomm/phy-qcom-m31.c new file mode 100644 index 0000000..fd568ef --- /dev/null +++ b/drivers/phy/qualcomm/phy-qcom-m31.c @@ -0,0 +1,256 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (c) 2014-2016, 2020, The Linux Foundation. All rights reserved. + */ + +#include <linux/clk.h> +#include <linux/delay.h> +#include <linux/err.h> +#include <linux/io.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/of_device.h> +#include <linux/of.h> +#include <linux/platform_device.h> +#include <linux/reset.h> +#include <linux/slab.h> +#include <linux/usb/of.h> +#include <linux/usb/phy.h> + +#define USB2PHY_PORT_UTMI_CTRL1 0x40 + +#define USB2PHY_PORT_UTMI_CTRL2 0x44 + #define UTMI_ULPI_SEL BIT(7) + #define UTMI_TEST_MUX_SEL BIT(6) + +#define HS_PHY_CTRL_REG 0x10 + #define UTMI_OTG_VBUS_VALID BIT(20) + #define SW_SESSVLD_SEL BIT(28) + +#define USB_PHY_UTMI_CTRL0 0x3c + +#define USB_PHY_UTMI_CTRL5 0x50 + #define POR_EN BIT(1) + #define ATERESET ~BIT(0) + +#define USB_PHY_HS_PHY_CTRL_COMMON0 0x54 + #define COMMONONN BIT(7) + #define FSEL BIT(4) + #define RETENABLEN BIT(3) + #define FREQ_24MHZ (5 << 4) + +#define USB_PHY_HS_PHY_CTRL2 0x64 + #define USB2_SUSPEND_N_SEL BIT(3) + #define USB2_SUSPEND_N BIT(2) + #define USB2_UTMI_CLK_EN BIT(1) + +#define USB_PHY_CFG0 0x94 + #define UTMI_PHY_OVERRIDE_EN BIT(1) + +#define USB_PHY_REFCLK_CTRL 0xa0 + #define CLKCORE BIT(1) + +#define USB2PHY_PORT_POWERDOWN 0xa4 + #define POWER_UP BIT(0) + #define POWER_DOWN 0 + +#define USB_PHY_FSEL_SEL 0xb8 + #define FREQ_SEL BIT(0) + +#define USB2PHY_USB_PHY_M31_XCFGI_1 0xbc + #define USB2_0_TX_ENABLE BIT(2) + +#define USB2PHY_USB_PHY_M31_XCFGI_4 0xc8 + #define HSTX_SLEW_RATE_565PS GENMASK(1, 0) + #define PLL_CHARGING_PUMP_CURRENT_35UA GENMASK(4, 3) + #define ODT_VALUE_38_02_OHM GENMASK(7, 6) + +#define USB2PHY_USB_PHY_M31_XCFGI_5 0xcc + #define ODT_VALUE_45_02_OHM BIT(2) + #define HSTX_PRE_EMPHASIS_LEVEL_0_55MA BIT(0) + +#define USB2PHY_USB_PHY_M31_XCFGI_11 0xe4 + #define XCFG_COARSE_TUNE_NUM BIT(1) + #define XCFG_FINE_TUNE_NUM BIT(3) + +struct m31_phy_regs { + u32 off; + u32 val; + u32 delay; +}; + +struct m31_priv_data { + bool ulpi_mode; + const struct m31_phy_regs *regs; +}; + +#define M31_REG(__o, __v, __d) \ + { .off = __o, .val = __v, .delay = __d } + +#define M31_REG_INVALID 0xffffffffu + +struct m31_phy_regs m31_ipq5332_regs[] = { + M31_REG(USB_PHY_CFG0, UTMI_PHY_OVERRIDE_EN, 0), + M31_REG(USB_PHY_UTMI_CTRL5, POR_EN, 15), + M31_REG(USB_PHY_FSEL_SEL, FREQ_SEL, 0), + M31_REG(USB_PHY_HS_PHY_CTRL_COMMON0, + COMMONONN | FREQ_24MHZ | RETENABLEN, 0), + M31_REG(USB_PHY_UTMI_CTRL5, POR_EN & ATERESET, 0), + M31_REG(USB_PHY_HS_PHY_CTRL2, + USB2_SUSPEND_N_SEL | USB2_SUSPEND_N | USB2_UTMI_CLK_EN, 0), + M31_REG(USB2PHY_USB_PHY_M31_XCFGI_11, + XCFG_COARSE_TUNE_NUM | XCFG_FINE_TUNE_NUM, 0), + M31_REG(USB2PHY_USB_PHY_M31_XCFGI_4, + HSTX_SLEW_RATE_565PS | PLL_CHARGING_PUMP_CURRENT_35UA | + ODT_VALUE_38_02_OHM, 0), + M31_REG(USB2PHY_USB_PHY_M31_XCFGI_1, USB2_0_TX_ENABLE, 0), + M31_REG(USB2PHY_USB_PHY_M31_XCFGI_5, + ODT_VALUE_45_02_OHM | HSTX_PRE_EMPHASIS_LEVEL_0_55MA, 4), + M31_REG(USB_PHY_UTMI_CTRL5, 0x0, 0), + M31_REG(USB_PHY_HS_PHY_CTRL2, USB2_SUSPEND_N | USB2_UTMI_CLK_EN, 0), + M31_REG(M31_REG_INVALID, 0, 0), +}; + +struct m31usb_phy { + struct usb_phy phy; + void __iomem *base; + const struct m31_phy_regs *regs; + + struct clk *cfg_ahb_clk; + struct reset_control *phy_reset; + + bool cable_connected; + bool suspended; + bool ulpi_mode; +}; + +static void m31usb_phy_enable_clock(struct m31usb_phy *qphy) +{ + const struct m31_phy_regs *regs = qphy->regs; + + for (; regs->off != M31_REG_INVALID; regs++) { + writel(regs->val, qphy->base + regs->off); + if (regs->delay) + udelay(regs->delay); + } +} + +static int m31usb_phy_init(struct usb_phy *phy) +{ + int ret; + struct m31usb_phy *qphy = container_of(phy, struct m31usb_phy, phy); + + ret = clk_prepare_enable(qphy->cfg_ahb_clk); + if (ret) { + dev_err(phy->dev, "failed to enable cfg ahb clock, %d\n", ret); + return ret; + } + + /* Perform phy reset */ + reset_control_assert(qphy->phy_reset); + udelay(5); + reset_control_deassert(qphy->phy_reset); + + /* configure for ULPI mode if requested */ + if (qphy->ulpi_mode) + writel(0x0, qphy->base + USB2PHY_PORT_UTMI_CTRL2); + + /* Enable the PHY */ + writel(POWER_UP, qphy->base + USB2PHY_PORT_POWERDOWN); + + /* Make sure above write completed */ + wmb(); + + /* Turn on phy ref clock */ + m31usb_phy_enable_clock(qphy); + + return 0; +} + +static void m31usb_phy_shutdown(struct usb_phy *phy) +{ + struct m31usb_phy *qphy = container_of(phy, struct m31usb_phy, phy); + + /* Disable the PHY */ + writel_relaxed(POWER_DOWN, qphy->base + USB2PHY_PORT_POWERDOWN); + /* Make sure above write completed */ + wmb(); + + clk_disable_unprepare(qphy->cfg_ahb_clk); +} + +static int m31usb_phy_probe(struct platform_device *pdev) +{ + const struct m31_priv_data *data; + struct device *dev = &pdev->dev; + struct m31usb_phy *qphy; + int ret; + + qphy = devm_kzalloc(dev, sizeof(*qphy), GFP_KERNEL); + if (!qphy) + return -ENOMEM; + + qphy->phy.dev = dev; + + qphy->base = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(qphy->base)) + return PTR_ERR(qphy->base); + + qphy->phy_reset = devm_reset_control_get_exclusive_by_index(dev, 0); + if (IS_ERR(qphy->phy_reset)) + return PTR_ERR(qphy->phy_reset); + + qphy->cfg_ahb_clk = devm_clk_get(dev, "cfg_ahb"); + if (IS_ERR(qphy->cfg_ahb_clk)) { + ret = PTR_ERR(qphy->cfg_ahb_clk); + dev_err(dev, "failed to get cfg_ahb clock, %d\n", ret); + return ret; + } + + platform_set_drvdata(pdev, qphy); + + data = of_device_get_match_data(dev); + qphy->regs = data->regs; + qphy->ulpi_mode = data->ulpi_mode; + + qphy->phy.label = "m31-usb-phy"; + qphy->phy.init = m31usb_phy_init; + qphy->phy.shutdown = m31usb_phy_shutdown; + qphy->phy.type = USB_PHY_TYPE_USB2; + + ret = usb_add_phy_dev(&qphy->phy); + + return ret; +} + +static void m31usb_phy_remove(struct platform_device *pdev) +{ + struct m31usb_phy *qphy = platform_get_drvdata(pdev); + + usb_remove_phy(&qphy->phy); +} + +static const struct m31_priv_data m31_ipq5332_data = { + .ulpi_mode = false, + .regs = m31_ipq5332_regs, +}; + +static const struct of_device_id m31usb_phy_id_table[] = { + { .compatible = "qcom,ipq5332-usb-hsphy", .data = &m31_ipq5332_data }, + { }, +}; +MODULE_DEVICE_TABLE(of, m31usb_phy_id_table); + +static struct platform_driver m31usb_phy_driver = { + .probe = m31usb_phy_probe, + .remove_new = m31usb_phy_remove, + .driver = { + .name = "qcom-m31usb-phy", + .of_match_table = m31usb_phy_id_table, + }, +}; + +module_platform_driver(m31usb_phy_driver); + +MODULE_DESCRIPTION("USB2 Qualcomm M31 HSPHY driver"); +MODULE_LICENSE("GPL");
Add the M31 USB2 phy driver. Signed-off-by: Varadarajan Narayanan <quic_varada@quicinc.com> --- v4: Remove unused enum Error handling for devm_clk_get v1: Combine driver, makefile and kconfig into 1 patch Remove 'qscratch' region and its usage. The controller driver takes care of those settings Use compatible/data to handle ipq5332 init Drop the default case Get resources by index instead of name as there is only one resource Add clock Fix review comments in the driver --- drivers/phy/qualcomm/Kconfig | 11 ++ drivers/phy/qualcomm/Makefile | 1 + drivers/phy/qualcomm/phy-qcom-m31.c | 256 ++++++++++++++++++++++++++++++++++++ 3 files changed, 268 insertions(+) create mode 100644 drivers/phy/qualcomm/phy-qcom-m31.c