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Date:   Sun, 25 Jun 2017 18:06:44 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Baolin Wang <baolin.wang@...eadtrum.com>
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Baolin Wang <baolin.wang@...aro.org>
Subject: Re: [PATCH v2 2/2] i2c: Add Spreadtrum I2C controller driver

On Wed, Jun 21, 2017 at 10:23 AM, Baolin Wang
<baolin.wang@...eadtrum.com> wrote:
> This patch adds the I2C controller driver for Spreadtrum platform.

Needs more work.
See my comments below.



> +#include <linux/init.h>

> +#include <linux/module.h>

Since your answer to the comment about arch_initcall you perhaps need
to get rid of tristate (use bool) and drop module.h here and all
leftovers like MODULE_*() calls.

> +#include <linux/slab.h>

Should we include this still explicitly (after kernel.h)?

> +
> +#define I2C_CTL                        0x0
> +#define I2C_ADDR_CFG           0x4
> +#define I2C_COUNT              0x8
> +#define I2C_RX                 0xC
> +#define I2C_TX                 0x10
> +#define I2C_STATUS             0x14
> +#define I2C_HSMODE_CFG         0x18
> +#define I2C_VERSION            0x1C
> +#define ADDR_DVD0              0x20
> +#define ADDR_DVD1              0x24
> +#define ADDR_STA0_DVD          0x28
> +#define ADDR_RST               0x2C

1. Please, use fixed sized values
0x00 and so on.
2. Please, low case.

> +#define SPRD_I2C_TIMEOUT       (msecs_to_jiffies(1000))

Redundant parens.

> +static void sprd_i2c_dump_reg(struct sprd_i2c *i2c_dev)

If you switch your driver to regmap API, you may drop this function completely.

> +               writel(tmp & (~STP_EN), i2c_dev->base + I2C_CTL);

Redundant parens.
Also pay attention to other similar places.


> +static void sprd_i2c_write_bytes(struct sprd_i2c *i2c_dev, u8 *buf, u32 len)

So, isn't better to provide a writesb(), readsb() to ia64 instead of
doing below?

> +{
> +       u32 i = 0;
> +
> +       for (i = 0; i < len; i++) {
> +               writel(buf[i], i2c_dev->base + I2C_TX);

> +               dev_dbg(&i2c_dev->adap.dev, "write bytes[%d] = %x\n", i, buf[i]);

Moreover, don't waste lines in the kernel log buffer by doing this.
Choose either

%*ph (up to 64 bytes)

or

print_hex_dump()

(Same for _read_bytes() below)

> +       }
> +}

> +static void sprd_i2c_set_full_thld(struct sprd_i2c *i2c_dev, u32 full_thld)
> +{
> +       unsigned int tmp = readl(i2c_dev->base + I2C_CTL);
> +
> +       tmp &= ~(0xf << FIFO_AF_LVL);

Magic.
Define it using GENMASK()

> +       tmp |= (full_thld << FIFO_AF_LVL);

Redundant parens.

> +       tmp &= ~(0xf << FIFO_AE_LVL);
> +       tmp |= (empty_thld << FIFO_AE_LVL);

Same.

> +static void sprd_i2c_opt_mode(struct sprd_i2c *i2c_dev, int rw)
> +{
> +       unsigned int cmd = readl(i2c_dev->base + I2C_CTL) & (~I2C_MODE);

Redundant parens.

> +       writel((cmd | rw << 3), i2c_dev->base + I2C_CTL);

Ditto.

It's a C, and not a LISP :-)

> +}

> +static void sprd_i2c_data_transfer(struct sprd_i2c *i2c_dev)
> +{

> +       if ((msg->flags & I2C_M_RD)) {

Redundant parens.

> +       /* Reset rx/tx fifos */

Noise.

> +       /* Set device address */

Ditto.

> +       /* Set I2C read or write bytes count */

Ditto.

> +       if ((msg->flags & I2C_M_RD)) {
> +               /* Set read operation */
> +               sprd_i2c_opt_mode(i2c_dev, 1);
> +               /* Last byte transmission should excute stop operation */
> +               sprd_i2c_send_stop(i2c_dev, 1);

Same comments as above.

> +       } else {

> +               /* Set write operation */

Noise.

> +               /* Last byte transmission should excute stop operation */
> +               if (is_last_msg)
> +                       sprd_i2c_send_stop(i2c_dev, 1);
> +               else
> +                       sprd_i2c_send_stop(i2c_dev, 0);

    sprd_i2c_send_stop(i2c_dev, !!is_last_msg);

Though, consider to make is_last_msg boolean.

> +static int sprd_i2c_master_xfer(struct i2c_adapter *i2c_adap,
> +                               struct i2c_msg *msgs, int num)
> +{
> +       struct sprd_i2c *i2c_dev = i2c_adap->algo_data;
> +       int im, ret;
> +
> +       ret = pm_runtime_get_sync(i2c_dev->dev);
> +       if (ret < 0)
> +               return ret;
> +

> +       for (im = 0; im != num; im++)

im < num - 1, and...

        ret = sprd_i2c_handle_msg(i2c_adap, &msgs[im], 0);
... ret = sprd_i2c_handle_msg(i2c_adap, &msgs[im++], 1);

...and we clearly see that you have messed up with returned code on
each itteration here

> +       pm_runtime_mark_last_busy(i2c_dev->dev);
> +       pm_runtime_put_autosuspend(i2c_dev->dev);


> +       return (ret >= 0) ? im : ret;

Usual pattern is
ret < 0 ? ret : im;


> +static void sprd_i2c_set_clk(struct sprd_i2c *i2c_dev, unsigned int freq)
> +{
> +       u32 apb_clk = i2c_dev->src_clk;
> +       u32 i2c_dvd = apb_clk / (4 * freq) - 1;
> +       u32 high = ((i2c_dvd << 1) * 2) / 5;
> +       u32 low = ((i2c_dvd << 1) * 3) / 5;

> +       u32 div0 = (high & 0xffff) << 16 | (low & 0xffff);
> +       u32 div1 =  (high & 0xffff0000) | ((low & 0xffff0000) >> 16);

Magic masks all over.

Also it needs a comment what formula is used and how.

> +
> +       writel(div0, i2c_dev->base + ADDR_DVD0);
> +       writel(div1, i2c_dev->base + ADDR_DVD1);
> +

> +       if (freq == 400000)
> +               writel((6 * apb_clk) / 10000000, i2c_dev->base + ADDR_STA0_DVD);
> +       else if (freq == 100000)
> +               writel((4 * apb_clk) / 1000000, i2c_dev->base + ADDR_STA0_DVD);

What about 3400000?

What about the rest of the speeds, shouldn't you return an error from here?

> +}
> +
> +static void sprd_i2c_enable(struct sprd_i2c *i2c_dev)
> +{
> +       unsigned int tmp = readl(i2c_dev->base + I2C_CTL);
> +
> +       tmp &= ~(I2C_EN | I2C_TRIM_OPT | (0xF << FIFO_AF_LVL) |
> +                (0xF << FIFO_AE_LVL));

Magic masks (I saw them already above).


> +       /* Set rx fifo full data threshold */

Drop noise comments. They don't bring any value since you have nice
function names.

> +       sprd_i2c_set_full_thld(i2c_dev, I2C_FIFO_FULL_THLD);
> +       /* Set tx fifo empty data threshold */
> +       sprd_i2c_set_empty_thld(i2c_dev, I2C_FIFO_EMPTY_THLD);
> +
> +       sprd_i2c_set_clk(i2c_dev, i2c_dev->bus_freq);
> +       /* Reset rx/tx fifo */
> +       sprd_i2c_reset_fifo(i2c_dev);
> +       sprd_i2c_clear_irq(i2c_dev);

> +static int sprd_i2c_clk_init(struct sprd_i2c *i2c_dev)
> +{
> +       struct clk *clk_i2c, *clk_parent;
> +       struct device_node *np = i2c_dev->adap.dev.of_node;
> +

> +       clk_i2c = of_clk_get_by_name(np, "i2c");

What the issue to use resource agnostic API here, i.e. devm_clk_get() ?

> +       clk_parent = of_clk_get_by_name(np, "source");

Ditto.

> +       i2c_dev->clk = of_clk_get_by_name(np, "enable");

Ditto.

> +       if (!of_property_read_u32(dev->of_node, "clock-frequency", &prop))
> +               i2c_dev->bus_freq = prop;
> +
> +       sprd_i2c_clk_init(i2c_dev);
> +       platform_set_drvdata(pdev, i2c_dev);
> +
> +       ret = clk_prepare_enable(i2c_dev->clk);
> +       if (ret)
> +               return ret;
> +
> +       sprd_i2c_enable(i2c_dev);
> +

> +error:

I would put it as

err_rpm_put:

> +       pm_runtime_put_noidle(i2c_dev->dev);
> +       pm_runtime_disable(i2c_dev->dev);
> +       clk_disable_unprepare(i2c_dev->clk);
> +       return ret;
> +}

-- 
With Best Regards,
Andy Shevchenko

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