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

Boris BREZILLON
2014-04-25T07:50:23Z

Hi Maxime,

On 24/04/2014 15:29, Maxime Ripard wrote:
> On Thu, Apr 24, 2014 at 01:55:16PM +0200, Boris BREZILLON wrote:
>> 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-sunxi-p2wi.c | 317 ++++++++++++++++++++++++++++++++++++
>> 3 files changed, 330 insertions(+)
>> create mode 100644 drivers/i2c/busses/i2c-sunxi-p2wi.c
>>
>> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
>> index c94db1c..37e53d6 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_SUNXI_P2WI
>> + tristate "Allwinner sunxi internal P2WI controller"
> Since the A31 is the only SoC that uses it, maybe you can drop the
> sunxi and use either sun6i or A31 here?

It makes sense, I'll change the config option into I2C_SUNXI_P2WI and
the source file name into i2c-sun6i-p2wi.c.

>> + 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..c63d2ec 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-$(CONFIG_I2C_SUNXI_P2WI) += i2c-sunxi-p2wi.o
>> obj-$(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-sunxi-p2wi.c b/drivers/i2c/busses/i2c-sunxi-p2wi.c
>> new file mode 100644
>> index 0000000..e3fdd76
>> --- /dev/null
>> +++ b/drivers/i2c/busses/i2c-sunxi-p2wi.c
>> @@ -0,0 +1,317 @@
>> +/*
>> + * 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_START_TRANS (1 << 7)
>> +#define P2WI_ABORT_TRANS (1 << 6)
>> +#define P2WI_GLOBAL_INT_ENB (1 << 1)
>> +#define P2WI_SOFT_RST (1 << 0)
> BIT() ?

Sure, I'll make use of the BIT macro wherever possible.

>
>> +/* CLK CTRL fields */
>> +#define P2WI_SDA_OUT_DELAY(v) (((v) & 0x7) << 8)
>> +#define P2WI_CLK_DIV(v) ((v) & 0xff)
>> +
>> +/* STATUS fields */
>> +#define P2WI_TRANS_ERR_ID(v) (((v) >> 8) & 0xff)
>> +#define P2WI_LOAD_BSY (1 << 2)
>> +#define P2WI_TRANS_ERR (1 << 1)
>> +#define P2WI_TRANS_OVER (1 << 0)
>> +
>> +/* DATA LENGTH fields*/
>> +#define P2WI_READ (1 << 4)
>> +#define P2WI_DATA_LENGTH(v) ((v - 1) & 0x7)
>> +
>> +/* LINE CTRL fields*/
>> +#define P2WI_SCL_STATE (1 << 5)
>> +#define P2WI_SDA_STATE (1 << 4)
>> +#define P2WI_SCL_CTL (1 << 3)
>> +#define P2WI_SCL_CTL_EN (1 << 2)
>> +#define P2WI_SDA_CTL (1 << 1)
>> +#define P2WI_SDA_CTL_EN (1 << 0)
>> +
>> +/* PMU MODE CTRL fields */
>> +#define P2WI_PMU_INIT_SEND (1 << 31)
>> +#define P2WI_PMU_INIT_DATA(v) (((v) & 0xff) << 16)
>> +#define P2WI_PMU_MODE_REG(v) (((v) & 0xff) << 8)
>> +#define P2WI_PMU_DEV_ADDR(v) ((v) & 0xff)
> I'd very much prefer if your bits were prefixed by the register
> name. That way, you directly know in which register that bit belong,
> without having to scroll across the whole driver.

Okay.

>> +
>> +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;
>> +};
>> +
>> +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_LOAD_BSY | P2WI_TRANS_ERR | P2WI_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_DATA_LENGTH(1);
>> +
>> + /*
>> + * TODO: check address consistency.
>> + * The P2WI bus only support one slave. As a result it does not use
>> + * the I2C address except when you're switching the slave device from
>> + * I2C to P2WI mode.
>> + * We should at least verify that the addr argument is consistent with
>> + * the slave device address.
>> + */
>> +
>> + if (addr > 0xff) {
>> + dev_err(&adap->dev, "invalid P2WI address\n");
>> + return -EINVAL;
>> + }
>> +
>> + /*
>> + * TODO: handle switch to P2WI mode.
>> + * At the moment, we're considering the slave device as already
>> + * switchedto P2WI (which means the bootloader has to switch the slave
> ^ you need a space here
>
>> + * device from I2C to P2WI mode).
>> + * We need at least 3 informations to launch the switch process:
>> + * - the slave device address (addr argument)
>> + * - the mode register
>> + * - the P2WI mode value (to write in the mode register)
>> + */
>> +
>> + if (!data)
>> + return -EINVAL;
>> +
>> + writel(command, p2wi->regs + P2WI_DADDR0);
>> +
>> + if (read_write == I2C_SMBUS_READ)
>> + dlen |= P2WI_READ;
>> + else
>> + writel(data->byte, p2wi->regs + P2WI_DATA0);
>> +
>> + writel(dlen, p2wi->regs + P2WI_DLEN);
>> +
>> + if (readl(p2wi->regs + P2WI_CTRL) & P2WI_START_TRANS) {
>> + dev_err(&adap->dev, "P2WI bus busy\n");
>> + return -EBUSY;
>> + }
>> +
>> + reinit_completion(&p2wi->complete);
>> +
>> + writel(P2WI_LOAD_BSY | P2WI_TRANS_ERR | P2WI_TRANS_OVER,
>> + p2wi->regs + P2WI_INTE);
>> +
>> + writel(P2WI_START_TRANS | P2WI_GLOBAL_INT_ENB, p2wi->regs + P2WI_CTRL);
>> +
>> + wait_for_completion(&p2wi->complete);
>> +
>> + if (p2wi->status & P2WI_LOAD_BSY) {
>> + dev_err(&adap->dev, "P2WI bus busy\n");
>> + return -EBUSY;
>> + }
>> +
>> +
> You can drop the extra line here.
>
>> + if (p2wi->status & P2WI_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 resource *r;
>> + struct p2wi *p2wi;
>> + int ret;
>> +
>> + p2wi = devm_kzalloc(dev, sizeof(struct p2wi), GFP_KERNEL);
>> + if (!p2wi) {
>> + dev_err(dev, "failed to allocate p2wi struct\n");
>> + return -ENOMEM;
>> + }
>> +
>> + r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> + p2wi->regs = devm_request_and_ioremap(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;
>> + }
> I don't see how it can work, since, when it fails,
> devm_request_and_ioremap returns NULL. You probably meant
> devm_ioremap_resource.

Oops, just forgot devm_request_and_ioremap is returning NULL when it fails.
I'll fix it.

Thanks.

Best Regards,

Boris
> Thanks!
> Maxime
>

--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering