[PATCH v4 2/2] i2c: sunxi: add P2WI (Push/Pull 2 Wire Interface) controller support

Boris BREZILLON
2014-05-10T09:46:41Z

The P2WI looks like an SMBus controller which only supports byte data
transfers. But, it differs from standard SMBus protocol on several
aspects:
- it supports only one slave device, and thus drop the address field
- it adds a parity bit every 8bits of data
- only one read access is required to read a byte (instead of a read
followed by a write access in standard SMBus protocol)
- there's no Ack bit after each byte transfer

This means this bus cannot be used to interface with standard SMBus
devices (the only known device to support this interface is the AXP221
PMIC).

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
---
drivers/i2c/busses/Kconfig | 12 ++
drivers/i2c/busses/Makefile | 1 +
drivers/i2c/busses/i2c-sun6i-p2wi.c | 349 ++++++++++++++++++++++++++++++++++++
3 files changed, 362 insertions(+)
create mode 100644 drivers/i2c/busses/i2c-sun6i-p2wi.c

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index c94db1c..09bce1c 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -771,6 +771,18 @@ config I2C_STU300
This driver can also be built as a module. If so, the module
will be called i2c-stu300.

+config I2C_SUN6I_P2WI
+ tristate "Allwinner sun6i internal P2WI controller"
+ depends on ARCH_SUNXI
+ help
+ If you say yes to this option, support will be included for the
+ P2WI (Push/Pull 2 Wire Interface) controller embedded in some sunxi
+ SOCs.
+ The P2WI looks like an SMBus controller (which supports only byte
+ accesses), except that it only supports one slave device.
+ This interface is used to connect to specific PMIC devices (like the
+ AXP221).
+
config I2C_TEGRA
tristate "NVIDIA Tegra internal I2C controller"
depends on ARCH_TEGRA
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 18d18ff..58feeb9 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -75,6 +75,7 @@ obj-$(CONFIG_I2C_SIMTEC) += i2c-simtec.o
obj-$(CONFIG_I2C_SIRF) += i2c-sirf.o
obj-$(CONFIG_I2C_ST) += i2c-st.o
obj-$(CONFIG_I2C_STU300) += i2c-stu300.o
+obj-$(CONFIG_I2C_SUN6I_P2WI) += i2c-sun6i-p2wi.o
obj-$(CONFIG_I2C_TEGRA) += i2c-tegra.o
obj-$(CONFIG_I2C_VERSATILE) += i2c-versatile.o
obj-$(CONFIG_I2C_WMT) += i2c-wmt.o
diff --git a/drivers/i2c/busses/i2c-sun6i-p2wi.c b/drivers/i2c/busses/i2c-sun6i-p2wi.c
new file mode 100644
index 0000000..10f78d2
--- /dev/null
+++ b/drivers/i2c/busses/i2c-sun6i-p2wi.c
@@ -0,0 +1,349 @@
+/*
+ * P2WI (Push-Pull Two Wire Interface) bus driver.
+ *
+ * Author: Boris BREZILLON <boris.brezillon@free-electrons.com>
+ *
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2. This program is licensed "as is" without any warranty of any
+ * kind, whether express or implied.
+ */
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_irq.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/delay.h>
+#include <linux/clk.h>
+#include <linux/reset.h>
+
+
+/* P2WI registers */
+#define P2WI_CTRL 0x0
+#define P2WI_CCR 0x4
+#define P2WI_INTE 0x8
+#define P2WI_INTS 0xc
+#define P2WI_DADDR0 0x10
+#define P2WI_DADDR1 0x14
+#define P2WI_DLEN 0x18
+#define P2WI_DATA0 0x1c
+#define P2WI_DATA1 0x20
+#define P2WI_LCR 0x24
+#define P2WI_PMCR 0x28
+
+/* CTRL fields */
+#define P2WI_CTRL_START_TRANS BIT(7)
+#define P2WI_CTRL_ABORT_TRANS BIT(6)
+#define P2WI_CTRL_GLOBAL_INT_ENB BIT(1)
+#define P2WI_CTRL_SOFT_RST BIT(0)
+
+/* CLK CTRL fields */
+#define P2WI_CCR_SDA_OUT_DELAY(v) (((v) & 0x7) << 8)
+#define P2WI_CCR_MAX_CLK_DIV 0xff
+#define P2WI_CCR_CLK_DIV(v) ((v) & P2WI_CCR_MAX_CLK_DIV)
+
+/* STATUS fields */
+#define P2WI_INTS_TRANS_ERR_ID(v) (((v) >> 8) & 0xff)
+#define P2WI_INTS_LOAD_BSY BIT(2)
+#define P2WI_INTS_TRANS_ERR BIT(1)
+#define P2WI_INTS_TRANS_OVER BIT(0)
+
+/* DATA LENGTH fields*/
+#define P2WI_DLEN_READ BIT(4)
+#define P2WI_DLEN_DATA_LENGTH(v) ((v - 1) & 0x7)
+
+/* LINE CTRL fields*/
+#define P2WI_LCR_SCL_STATE BIT(5)
+#define P2WI_LCR_SDA_STATE BIT(4)
+#define P2WI_LCR_SCL_CTL BIT(3)
+#define P2WI_LCR_SCL_CTL_EN BIT(2)
+#define P2WI_LCR_SDA_CTL BIT(1)
+#define P2WI_LCR_SDA_CTL_EN BIT(0)
+
+/* PMU MODE CTRL fields */
+#define P2WI_PMCR_PMU_INIT_SEND BIT(31)
+#define P2WI_PMCR_PMU_INIT_DATA(v) (((v) & 0xff) << 16)
+#define P2WI_PMCR_PMU_MODE_REG(v) (((v) & 0xff) << 8)
+#define P2WI_PMCR_PMU_DEV_ADDR(v) ((v) & 0xff)
+
+#define P2WI_MAX_FREQ 6000000
+
+struct p2wi {
+ struct i2c_adapter adapter;
+ struct completion complete;
+ unsigned int irq;
+ unsigned int status;
+ void __iomem *regs;
+ struct clk *clk;
+ struct reset_control *rstc;
+ int slave_addr;
+};
+
+static irqreturn_t p2wi_interrupt(int irq, void *dev_id)
+{
+ struct p2wi *p2wi = dev_id;
+ unsigned long status;
+
+ status = readl(p2wi->regs + P2WI_INTS);
+ p2wi->status = status;
+
+ /* Clear interrupts */
+ status &= (P2WI_INTS_LOAD_BSY | P2WI_INTS_TRANS_ERR |
+ P2WI_INTS_TRANS_OVER);
+ writel(status, p2wi->regs + P2WI_INTS);
+
+ complete(&p2wi->complete);
+
+ return IRQ_HANDLED;
+}
+
+static u32 p2wi_functionality(struct i2c_adapter *adap)
+{
+ return I2C_FUNC_SMBUS_BYTE_DATA;
+}
+
+static int p2wi_smbus_xfer(struct i2c_adapter *adap, u16 addr,
+ unsigned short flags, char read_write,
+ u8 command, int size, union i2c_smbus_data *data)
+{
+ struct p2wi *p2wi = i2c_get_adapdata(adap);
+ unsigned long dlen = P2WI_DLEN_DATA_LENGTH(1);
+
+ if (addr > 0xff ||
+ (p2wi->slave_addr >= 0 && addr != p2wi->slave_addr)) {
+ dev_err(&adap->dev, "invalid P2WI address\n");
+ return -EINVAL;
+ }
+
+ if (!data)
+ return -EINVAL;
+
+ writel(command, p2wi->regs + P2WI_DADDR0);
+
+ if (read_write == I2C_SMBUS_READ)
+ dlen |= P2WI_DLEN_READ;
+ else
+ writel(data->byte, p2wi->regs + P2WI_DATA0);
+
+ writel(dlen, p2wi->regs + P2WI_DLEN);
+
+ if (readl(p2wi->regs + P2WI_CTRL) & P2WI_CTRL_START_TRANS) {
+ dev_err(&adap->dev, "P2WI bus busy\n");
+ return -EBUSY;
+ }
+
+ reinit_completion(&p2wi->complete);
+
+ writel(P2WI_INTS_LOAD_BSY | P2WI_INTS_TRANS_ERR | P2WI_INTS_TRANS_OVER,
+ p2wi->regs + P2WI_INTE);
+
+ writel(P2WI_CTRL_START_TRANS | P2WI_CTRL_GLOBAL_INT_ENB,
+ p2wi->regs + P2WI_CTRL);
+
+ wait_for_completion(&p2wi->complete);
+
+ if (p2wi->status & P2WI_INTS_LOAD_BSY) {
+ dev_err(&adap->dev, "P2WI bus busy\n");
+ return -EBUSY;
+ }
+
+ if (p2wi->status & P2WI_INTS_TRANS_ERR) {
+ dev_err(&adap->dev, "P2WI bus xfer error\n");
+ return -ENXIO;
+ }
+
+ if (read_write == I2C_SMBUS_READ)
+ data->byte = readl(p2wi->regs + P2WI_DATA0);
+
+ return 0;
+}
+
+static const struct i2c_algorithm p2wi_algo = {
+ .smbus_xfer = p2wi_smbus_xfer,
+ .functionality = p2wi_functionality,
+};
+
+static const struct of_device_id p2wi_of_match_table[] = {
+ { .compatible = "allwinner,sun6i-a31-p2wi" },
+ {}
+};
+MODULE_DEVICE_TABLE(of, p2wi_of_match_table);
+
+static int p2wi_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *np = dev->of_node;
+ struct device_node *childnp;
+ unsigned long parent_clk_freq;
+ u32 clk_freq = 100000;
+ struct resource *r;
+ struct p2wi *p2wi;
+ u32 slave_addr;
+ int clk_div;
+ int ret;
+
+ of_property_read_u32(np, "clock-frequency", &clk_freq);
+ if (clk_freq > P2WI_MAX_FREQ) {
+ dev_err(dev,
+ "required clock-frequency (%u Hz) is too high (max = 6MHz)",
+ clk_freq);
+ return -EINVAL;
+ }
+
+ if (of_get_child_count(np) > 1) {
+ dev_err(dev, "P2WI only supports one slave device\n");
+ return -EINVAL;
+ }
+
+ p2wi = devm_kzalloc(dev, sizeof(struct p2wi), GFP_KERNEL);
+ if (!p2wi) {
+ dev_err(dev, "failed to allocate p2wi struct\n");
+ return -ENOMEM;
+ }
+
+ p2wi->slave_addr = -1;
+
+ /*
+ * Authorize a p2wi node without any children to be able to use an
+ * i2c-dev from userpace.
+ * In this case the slave_addr is set to -1 and won't be checked when
+ * launching a P2WI transfer.
+ */
+ childnp = of_get_next_available_child(np, NULL);
+ if (childnp) {
+ ret = of_property_read_u32(childnp, "reg", &slave_addr);
+ if (ret || slave_addr > 0xff) {
+ dev_err(dev, "invalid slave address on node %s\n",
+ childnp->full_name);
+ return -EINVAL;
+ }
+
+ p2wi->slave_addr = slave_addr;
+ }
+
+ r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ p2wi->regs = devm_ioremap_resource(dev, r);
+ if (IS_ERR(p2wi->regs)) {
+ ret = PTR_ERR(p2wi->regs);
+ dev_err(dev, "failed to retrieve iomem resource: %d\n", ret);
+ return ret;
+ }
+
+ snprintf(p2wi->adapter.name, sizeof(p2wi->adapter.name), pdev->name);
+ ret = platform_get_irq(pdev, 0);
+ if (ret < 0) {
+ dev_err(dev, "failed to retrieve irq: %d\n", ret);
+ return ret;
+ }
+ p2wi->irq = ret;
+
+ p2wi->clk = devm_clk_get(dev, NULL);
+ if (IS_ERR(p2wi->clk)) {
+ ret = PTR_ERR(p2wi->clk);
+ dev_err(dev, "failed to retrieve clk: %d\n",
+ ret);
+ return ret;
+ }
+
+ ret = clk_prepare_enable(p2wi->clk);
+ if (ret) {
+ dev_err(dev, "failed to enable clk: %d\n", ret);
+ return ret;
+ }
+
+ parent_clk_freq = clk_get_rate(p2wi->clk);
+
+ p2wi->rstc = devm_reset_control_get(dev, NULL);
+ if (IS_ERR(p2wi->rstc)) {
+ ret = PTR_ERR(p2wi->rstc);
+ dev_err(dev, "failed to retrieve reset controller: %d\n",
+ ret);
+ goto err_clk_disable;
+ }
+
+ ret = reset_control_deassert(p2wi->rstc);
+ if (ret) {
+ dev_err(dev, "failed to deassert reset line: %d\n",
+ ret);
+ goto err_clk_disable;
+ }
+
+ init_completion(&p2wi->complete);
+ p2wi->adapter.dev.parent = dev;
+ p2wi->adapter.algo = &p2wi_algo;
+ p2wi->adapter.owner = THIS_MODULE;
+ p2wi->adapter.dev.of_node = pdev->dev.of_node;
+ platform_set_drvdata(pdev, p2wi);
+ i2c_set_adapdata(&p2wi->adapter, p2wi);
+
+ ret = devm_request_irq(dev, p2wi->irq, p2wi_interrupt, 0, pdev->name,
+ p2wi);
+ if (ret) {
+ dev_err(dev, "can't register interrupt handler irq%d: %d\n",
+ p2wi->irq, ret);
+ goto err_reset_assert;
+ }
+
+ writel(P2WI_CTRL_SOFT_RST, p2wi->regs + P2WI_CTRL);
+
+ clk_div = parent_clk_freq / clk_freq;
+ if (!clk_div) {
+ dev_warn(dev,
+ "clock-frequency is too high, setting it to %lu Hz\n",
+ parent_clk_freq);
+ clk_div = 1;
+ } else if (clk_div > P2WI_CCR_MAX_CLK_DIV) {
+ dev_warn(dev,
+ "clock-frequency is too low, setting it to %lu Hz\n",
+ parent_clk_freq / P2WI_CCR_MAX_CLK_DIV);
+ clk_div = P2WI_CCR_MAX_CLK_DIV;
+ }
+
+ writel(P2WI_CCR_SDA_OUT_DELAY(1) | P2WI_CCR_CLK_DIV(clk_div),
+ p2wi->regs + P2WI_CCR);
+
+ ret = i2c_add_adapter(&p2wi->adapter);
+ if (!ret)
+ return 0;
+
+err_reset_assert:
+ reset_control_assert(p2wi->rstc);
+
+err_clk_disable:
+ clk_disable_unprepare(p2wi->clk);
+
+ return ret;
+}
+
+static int p2wi_remove(struct platform_device *dev)
+{
+ struct p2wi *p2wi = platform_get_drvdata(dev);
+
+ reset_control_assert(p2wi->rstc);
+ clk_disable_unprepare(p2wi->clk);
+ i2c_del_adapter(&p2wi->adapter);
+
+ return 0;
+}
+
+static struct platform_driver p2wi_driver = {
+ .probe = p2wi_probe,
+ .remove = p2wi_remove,
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "i2c-sunxi-p2wi",
+ .of_match_table = p2wi_of_match_table,
+ },
+};
+module_platform_driver(p2wi_driver);
+
+MODULE_AUTHOR("Boris BREZILLON <boris.brezillon@free-electrons.com>");
+MODULE_DESCRIPTION("Allwinner P2WI driver");
+MODULE_LICENSE("GPL");
--
1.8.3.2