Hello Wolfram, On 10/06/2014 10:38, Wolfram Sang wrote: > On Tue, Jun 03, 2014 at 10:49:52AM +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). > Good description. Should be a comment at the top of the driver to spread > the word.
Sure, I'll copy this description in the driver. >> Signed-off-by: Boris BREZILLON <[email protected]> >> Acked-by: Maxime Ripard <[email protected]> >> --- >> 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 > ... > >> +struct p2wi { >> + struct i2c_adapter adapter; >> + struct completion complete; >> + unsigned int irq; > Can be a local variable in probe. Yes, I'll remove it from this structure. > >> + 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 || > Why 0xff? Does the PMIC support that? I2C addresses are 7-bit. You > won't even have a slave device if it has an illegal i2c address, so this > shouldn't happen. The P2WI protocol supports 8bits addresses, hence I added this 0xff check. Anyway, the PMIC I use (AXP221) is assigned the 0x68 address, and I don't think there are a lot of P2WI compatible devices in the wild, so we can just assume 7bits addresses are fine and rely on the core code checks. > >> + (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"); > No error strings for OOM. I'll drop this line. > >> + 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) { > Again: Is 8 bit range important here? Otherwise I'd leave the check to the > core. > >> + 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); > devm_ioremap_resource prints errors on its own. Ditto > >> + 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); > My general suggestion: Don't be too strict on the 80 char limit. IMO this > dangling > 'ret' is not more readable. Okay, I'll fix that. Thanks for your review. Best Regards, Boris -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
