On Sat, Jun 13, 2015 at 4:26 PM, Ellen Wang <ellen@xxxxxxxxxxxxxxxxxxx> wrote:
> cp2112_i2c_xfer() only supports a single i2c_msg and only
> reads up to 61 bytes. More than one message at a time
> and longers reads just return errors. This breaks certain
> important cases. For example, the at24 eeprom driver generates
> paired write and read messages (for eeprom address and data).
> And the reads can be larger than 61 bytes.
>
> Since the device doesn't support i2c repeated starts in general,
> but does support a single write-repeated-start-read pair
> (as CP2112_DATA_WRITE_READ_REQUEST), we recognize the latter
> case and implement only that.
>
> To support large reads, we wrap a loop around cp2112_read()
> to pick up all the returned data.
Hi Ellen,
to keep git log consistent, the subject should change to something like
HID: cp2112: ...
Actually you are adding two features.
I think should be better to split them in two independent patches.
> Signed-off-by: Ellen Wang <ellen@xxxxxxxxxxxxxxxxxxx>
> ---
> As Antonio Borneo and I discussed previously, this is the updated
> patch that preserves the repeated start semantics (by not incorrectly
> implementing cases that don't work).
>
> Thank you for your time!
> ---
> drivers/hid/hid-cp2112.c | 79 +++++++++++++++++++++++++++++++++-------------
> 1 file changed, 57 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/hid/hid-cp2112.c b/drivers/hid/hid-cp2112.c
> index 3318de6..2c10a45 100644
> --- a/drivers/hid/hid-cp2112.c
> +++ b/drivers/hid/hid-cp2112.c
> @@ -444,6 +444,24 @@ static int cp2112_i2c_write_req(void *buf, u8 slave_address, u8 *data,
> return data_length + 3;
> }
>
> +static int cp2112_i2c_write_read_req(void *buf, u8 slave_address,
> + u8 *addr, int addr_length,
> + int read_length)
> +{
> + struct cp2112_write_read_req_report *report = buf;
> +
> + if (read_length < 1 || read_length > 512 ||
> + addr_length > sizeof(report->target_address))
> + return -EINVAL;
> +
> + report->report = CP2112_DATA_WRITE_READ_REQUEST;
> + report->slave_address = slave_address << 1;
> + report->length = cpu_to_be16(read_length);
> + report->target_address_length = addr_length;
> + memcpy(report->target_address, addr, addr_length);
> + return addr_length + 5;
> +}
> +
> static int cp2112_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> int num)
> {
> @@ -451,26 +469,45 @@ static int cp2112_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> struct hid_device *hdev = dev->hdev;
> u8 buf[64];
> ssize_t count;
> + ssize_t read_length = 0;
> + u8 *read_buf = NULL;
> unsigned int retries;
> int ret;
>
> hid_dbg(hdev, "I2C %d messages\n", num);
>
> - if (num != 1) {
> + if (num == 1) {
> + if (msgs->flags & I2C_M_RD) {
> + hid_dbg(hdev, "I2C read %#04x len %d\n",
> + msgs->addr, msgs->len);
> + read_length = msgs->len;
> + read_buf = msgs->buf;
> + count = cp2112_read_req(buf, msgs->addr, msgs->len);
> + } else {
> + hid_dbg(hdev, "I2C write %#04x len %d\n",
> + msgs->addr, msgs->len);
> + count = cp2112_i2c_write_req(buf, msgs->addr,
> + msgs->buf, msgs->len);
> + }
> + if (count < 0)
> + return count;
> + } else if (num == 2 &&
> + msgs[0].addr == msgs[1].addr &&
> + !(msgs[0].flags & I2C_M_RD) && (msgs[1].flags & I2C_M_RD)) {
> + hid_dbg(hdev, "I2C write-read %#04x wlen %d rlen %d\n",
> + msgs[0].addr, msgs[0].len, msgs[1].len);
> + read_length = msgs[1].len;
> + read_buf = msgs[1].buf;
> + count = cp2112_i2c_write_read_req(buf, msgs[0].addr,
> + msgs[0].buf, msgs[0].len, msgs[1].len);
> + if (count < 0)
> + return count;
> + } else {
> hid_err(hdev,
> "Multi-message I2C transactions not supported\n");
> return -EOPNOTSUPP;
> }
>
> - if (msgs->flags & I2C_M_RD)
> - count = cp2112_read_req(buf, msgs->addr, msgs->len);
> - else
> - count = cp2112_i2c_write_req(buf, msgs->addr, msgs->buf,
> - msgs->len);
> -
> - if (count < 0)
> - return count;
> -
> ret = hid_hw_power(hdev, PM_HINT_FULLON);
> if (ret < 0) {
> hid_err(hdev, "power management error: %d\n", ret);
The part above goes in a patch for write-read, the part below in
another patch for large transfers.
I have tested you patch and works fine; I can read an I2C eeprom.
But I also check with an oscilloscope the I2C signals and I got
disappointed. There is no repeated START.
I can clearly see cp2112 generating a STOP immediately followed by a START.
Datasheet of cp2112 in figure 8 reports the expected time diagram with
repeated START, but it's not what I get on my HW.
Your code seam ok. Maybe my device is outdated or broken.
The errata document from Silabs does not report anythink relevant.
Can you verify with a scope on your HW too?
Thanks,
Antonio
> @@ -506,21 +543,19 @@ static int cp2112_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> goto power_normal;
> }
>
> - if (!(msgs->flags & I2C_M_RD))
> - goto finish;
> -
> - ret = cp2112_read(dev, msgs->buf, msgs->len);
> - if (ret < 0)
> - goto power_normal;
> - if (ret != msgs->len) {
> - hid_warn(hdev, "short read: %d < %d\n", ret, msgs->len);
> - ret = -EIO;
> - goto power_normal;
> + for (count = 0; count < read_length;) {
> + ret = cp2112_read(dev, read_buf + count, read_length - count);
> + if (ret < 0)
> + goto power_normal;
> + count += ret;
> + if (count > read_length) {
> + hid_warn(hdev, "long read: %d > %zd\n",
> + ret, read_length - count + ret);
> + }
> }
>
> -finish:
> /* return the number of transferred messages */
> - ret = 1;
> + ret = num;
>
> power_normal:
> hid_hw_power(hdev, PM_HINT_NORMAL);
> --
> 1.7.10.4
>
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