[U-Boot] [PATCH v3 01/10] dm: i2c: Add a uclass for I2C

[Simon Glass]

Hi Masahiro,

On 1 December 2014 at 04:47, Masahiro Yamada <yamada.m at jp.panasonic.com> wrote:
> Hi Simon,
>
>
> My review is still under way,
> but I have some comments below:
>
>

Thanks again for the comments, will tidy up a few other things too
before sending v4.
>
>
> On Mon, 24 Nov 2014 11:57:15 -0700
> Simon Glass <sjg at chromium.org> wrote:
>
>> +static bool i2c_setup_offset(struct dm_i2c_chip *chip, uint offset,
>> +                          uint8_t offset_buf[], struct i2c_msg *msg)
>> +{
>> +     if (!chip->offset_len)
>> +             return false;
>> +     msg->addr = chip->chip_addr;
>> +     msg->flags = chip->flags;
>> +     msg->len = chip->offset_len;
>> +     msg->buf = offset_buf;
>
> You directly copy
> from  (struct dm_i2c_chip *)->flags
> to  (struct i2c_msg *)->flags.
>
> But you define completely different flags for them:
>   DM_I2C_CHIP_10BIT is defined as 0x1.
>   I2C_M_TEN  is defined as 0x10.
>
> It would not work.
>
>
>
>> +
>> +static int i2c_read_bytewise(struct udevice *dev, uint offset,
>> +                          const uint8_t *buffer, int len)
>> +{
>> +     struct dm_i2c_chip *chip = dev_get_parentdata(dev);
>> +     struct udevice *bus = dev_get_parent(dev);
>> +     struct dm_i2c_ops *ops = i2c_get_ops(bus);
>> +     struct i2c_msg msg[1];
>> +     uint8_t buf[5];
>> +     int ret;
>> +     int i;
>> +
>> +     for (i = 0; i < len; i++) {
>> +             i2c_setup_offset(chip, offset, buf, msg);
>> +             msg->len++;
>> +             buf[chip->offset_len] = buffer[i];
>> +
>> +             ret = ops->xfer(bus, msg, 1);
>> +             if (ret)
>> +                     return ret;
>> +     }
>> +
>> +     return 0;
>> +}
>
> I could not understand how this works.
> It seems to send only write transactions.

Yes this is the write function, I need to add a read function and rename...

>
>
>
>> +
>> +static int i2c_bind_driver(struct udevice *bus, uint chip_addr,
>> +                        struct udevice **devp)
>> +{
>> +     struct dm_i2c_chip *chip;
>> +     char name[30], *str;
>> +     struct udevice *dev;
>> +     int ret;
>> +
>> +     snprintf(name, sizeof(name), "generic_%x", chip_addr);
>> +     str = strdup(name);
>> +     ret = device_bind_driver(bus, "i2c_generic_drv", str, &dev);
>> +     debug("%s:  device_bind_driver: ret=%d\n", __func__, ret);
>> +     if (ret)
>> +             goto err_bind;
>> +
>> +     /* Tell the device what we know about it */
>> +     chip = calloc(1, sizeof(struct dm_i2c_chip));
>> +     if (!chip) {
>> +             ret = -ENOMEM;
>> +             goto err_mem;
>> +     }
>> +     chip->chip_addr = chip_addr;
>> +     chip->offset_len = 1;   /* we assume */
>> +     ret = device_probe_child(dev, chip);
>> +     debug("%s:  device_probe_child: ret=%d\n", __func__, ret);
>> +     free(chip);
>
>
> Why do you need calloc() & free() here?
> I think you can use the stack area for "struct dm_i2c_chip chip;"
>
>
>
>
>
>
>
>
>> +
>> +UCLASS_DRIVER(i2c) = {
>> +     .id             = UCLASS_I2C,
>> +     .name           = "i2c",
>> +     .per_device_auto_alloc_size = sizeof(struct dm_i2c_bus),
>> +     .post_bind      = i2c_post_bind,
>> +     .post_probe     = i2c_post_probe,
>> +};
>> +
>> +UCLASS_DRIVER(i2c_generic) = {
>> +     .id             = UCLASS_I2C_GENERIC,
>> +     .name           = "i2c_generic",
>> +};
>> +
>> +U_BOOT_DRIVER(i2c_generic_drv) = {
>
> Perhaps isn't "i2c_generic_chip" clearer than "i2c_generic_drv"?
>
>
>
>> +     .name           = "i2c_generic_drv",
>> +     .id             = UCLASS_I2C_GENERIC,
>> +};
>
>
> Can we move "i2c_generic" to a different file?
> maybe, drivers/i2c/i2c-generic.c or drivers/i2c/i2c-generic-chip.c ?
>
> UCLASS_DRIVER(i2c) is a bus, whereas UCLASS_DRIVER(i2c_generic) is a chip.
>
> Mixing up a bus and a chip-device together in the same file
> looks confusing to me.
>
>
>
>
>>
>>  /*
>> + * For now there are essentially two parts to this file - driver model
>> + * here at the top, and the older code below (with CONFIG_SYS_I2C being
>> + * most recent). The plan is to migrate everything to driver model.
>> + * The driver model structures and API are separate as they are different
>> + * enough as to be incompatible for compilation purposes.
>> + */
>> +
>> +#ifdef CONFIG_DM_I2C
>> +
>> +enum dm_i2c_chip_flags {
>> +     DM_I2C_CHIP_10BIT       = 1 << 0, /* Use 10-bit addressing */
>> +     DM_I2C_CHIP_RE_ADDRESS  = 1 << 1, /* Send address for every byte */
>> +};
>
>
> As I mentioned above, you define DM_I2C_CHIP_10BIT as 0x1
> whereas you define I2C_M_TEN as 0x0010.
>
> These flags should be shared with struct i2c_msg.
>
>
>
>> +/*
>> + * Not all of these flags are implemented in the U-Boot API
>> + */
>> +enum dm_i2c_msg_flags {
>> +     I2C_M_TEN               = 0x0010, /* ten-bit chip address */
>> +     I2C_M_RD                = 0x0001, /* read data, from slave to master */
>> +     I2C_M_STOP              = 0x8000, /* send stop after this message */
>> +     I2C_M_NOSTART           = 0x4000, /* no start before this message */
>> +     I2C_M_REV_DIR_ADDR      = 0x2000, /* invert polarity of R/W bit */
>> +     I2C_M_IGNORE_NAK        = 0x1000, /* continue after NAK */
>> +     I2C_M_NO_RD_ACK         = 0x0800, /* skip the Ack bit on reads */
>> +     I2C_M_RECV_LEN          = 0x0400, /* length is first received byte */
>> +};
>
> I think this enum usage is odd.
>
> If you want to allocate specific values such as 0x8000, 0x4000, etc.
> you should use #define instead of enum.
>
> If you do not care which value is assigned, you can use enum.
> arch/arm/include/asm/spl.h is a good example of usage of enum.

I prefer enum in most cases - it comes through nicely in the debugger
and I don't need brackets around everything.

>
>
>
>
>
>
>> +};
>> +
>> +/**
>> + * struct dm_i2c_ops - driver operations for I2C uclass
>> + *
>> + * Drivers should support these operations unless otherwise noted. These
>> + * operations are intended to be used by uclass code, not directly from
>> + * other code.
>> + */
>> +struct dm_i2c_ops {
>> +     /**
>> +      * xfer() - transfer a list of I2C messages
>> +      *
>> +      * @bus:        Bus to read from
>> +      * @chip_addr:  Chip address to read from
>> +      * @offset:     Offset within chip to start reading
>> +      * @olen:       Length of chip offset in bytes
>> +      * @buffer:     Place to put data
>> +      * @len:        Number of bytes to read
>> +      * @return 0 if OK, -EREMOTEIO if the slave did not ACK a byte,
>> +      *      other -ve value on some other error
>> +      */
>> +     int (*xfer)(struct udevice *bus, struct i2c_msg *msg, int nmsgs);
>
>
> This comment block does not reflect the actual prototype;
> chip_addr, offset, ... etc. do not exist any more.
>
>
>
>
>
> Best Regards
> Masahiro Yamada
>

Regards,
Simon