Hi Dinesh,
On Sun, Sep 1, 2013 at 10:42 AM, dinesh ram <dino_mc4@xxxxxxxxxxx> wrote:
> Hi Eduardo,
> Hi Hans,
>
> ________________________________
> From: Hans Verkuil <hverkuil@xxxxxxxxx>
> To: "edubezval@xxxxxxxxx" <edubezval@xxxxxxxxx>
> Cc: Dinesh Ram <dinram@xxxxxxxxx>; Linux-Media
> <linux-media@xxxxxxxxxxxxxxx>; dinesh.ram@xxxxxxx
> Sent: Sunday, 1 September 2013 12:57 PM
> Subject: Re: [PATCH 2/6] si4713 : Modified i2c driver to handle cases where
> interrupts are not used
>
> On 08/31/2013 01:31 PM, edubezval@xxxxxxxxx wrote:
>> Dinesh, Hi
>>
>>
>> On Fri, Aug 30, 2013 at 7:28 AM, Dinesh Ram <dinram@xxxxxxxxx> wrote:
>>>
>>> Checks have been introduced at several places in the code to test if an
>>> interrupt is set or not.
>>> For devices which do not use the interrupt, to get a valid response,
>>> within a specified timeout,
>>> the device is polled instead.
>>>
>>> Signed-off-by: Dinesh Ram <dinram@xxxxxxxxx>
>>> ---
>>> drivers/media/radio/si4713/si4713.c | 110
>>> ++++++++++++++++++++----------------
>>> drivers/media/radio/si4713/si4713.h | 1 +
>>> 2 files changed, 63 insertions(+), 48 deletions(-)
>>>
>>> diff --git a/drivers/media/radio/si4713/si4713.c
>>> b/drivers/media/radio/si4713/si4713.c
>>> index ac727e3..55c4d27 100644
>>> --- a/drivers/media/radio/si4713/si4713.c
>>> +++ b/drivers/media/radio/si4713/si4713.c
>>> @@ -27,7 +27,6 @@
>>> #include <linux/i2c.h>
>>> #include <linux/slab.h>
>>> #include <linux/gpio.h>
>>> -#include <linux/regulator/consumer.h>
>>> #include <linux/module.h>
>>> #include <media/v4l2-device.h>
>>> #include <media/v4l2-ioctl.h>
>>> @@ -213,6 +212,7 @@ static int si4713_send_command(struct si4713_device
>>> *sdev, const u8 command,
>>> u8 response[], const int respn, const int
>>> usecs)
>>> {
>>> struct i2c_client *client = v4l2_get_subdevdata(&sdev->sd);
>>> + unsigned long until_jiffies;
>>> u8 data1[MAX_ARGS + 1];
>>> int err;
>>>
>>> @@ -228,30 +228,39 @@ static int si4713_send_command(struct si4713_device
>>> *sdev, const u8 command,
>>> if (err != argn + 1) {
>>> v4l2_err(&sdev->sd, "Error while sending command
>>> 0x%02x\n",
>>> command);
>>> - return (err > 0) ? -EIO : err;
>>> + return err < 0 ? err : -EIO;
>>
>> Why did you change the semantics here?
>
> It's a bug fix: if i2c_master_send returns 0, then si4713_send_command()
> would
> return 0 as well instead of -EIO. Highly unlikely to ever happen, but it is
> a
> bug.
>
>>
>>> }
>>>
>>> + until_jiffies = jiffies + usecs_to_jiffies(usecs) + 1;
>>> +
>>> /* Wait response from interrupt */
>>> - if (!wait_for_completion_timeout(&sdev->work,
>>> + if (client->irq) {
>>> + if (!wait_for_completion_timeout(&sdev->work,
>>> usecs_to_jiffies(usecs) + 1))
>>> - v4l2_warn(&sdev->sd,
>>> + v4l2_warn(&sdev->sd,
>>> "(%s) Device took too much time to
>>> answer.\n",
>>> __func__);
>>> -
>>> - /* Then get the response */
>>> - err = i2c_master_recv(client, response, respn);
>>> - if (err != respn) {
>>> - v4l2_err(&sdev->sd,
>>> - "Error while reading response for command
>>> 0x%02x\n",
>>> - command);
>>> - return (err > 0) ? -EIO : err;
>>> }
>>>
>>> - DBG_BUFFER(&sdev->sd, "Response", response, respn);
>>> - if (check_command_failed(response[0]))
>>> - return -EBUSY;
>>> + do {
>>> + err = i2c_master_recv(client, response, respn);
>>> + if (err != respn) {
>>> + v4l2_err(&sdev->sd,
>>> + "Error %d while reading response
>>> for command 0x%02x\n",
>>> + err, command);
>>> + return err < 0 ? err : -EIO;
>>
>> Again?
>>
>>> + }
>>>
>>> - return 0;
>>> + DBG_BUFFER(&sdev->sd, "Response", response, respn);
>>> + if (!check_command_failed(response[0]))
>>> + return 0;
>>> +
>>> + if (client->irq)
>>> + return -EBUSY;
>>> + msleep(1);
>>> + } while (jiffies <= until_jiffies);
>>> +
>>> + return -EBUSY;
>>> }
>>>
>>> /*
>>> @@ -344,14 +353,15 @@ static int si4713_write_property(struct
>>> si4713_device *sdev, u16 prop, u16 val)
>>> */
>>> static int si4713_powerup(struct si4713_device *sdev)
>>> {
>>> + struct i2c_client *client = v4l2_get_subdevdata(&sdev->sd);
>>> int err;
>>> u8 resp[SI4713_PWUP_NRESP];
>>> /*
>>> * .First byte = Enabled interrupts and boot function
>>> * .Second byte = Input operation mode
>>> */
>>> - const u8 args[SI4713_PWUP_NARGS] = {
>>> - SI4713_PWUP_CTSIEN | SI4713_PWUP_GPO2OEN |
>>> SI4713_PWUP_FUNC_TX,
>>> + u8 args[SI4713_PWUP_NARGS] = {
>>> + SI4713_PWUP_GPO2OEN | SI4713_PWUP_FUNC_TX,
>>> SI4713_PWUP_OPMOD_ANALOG,
>>> };
>>>
>>> @@ -369,18 +379,22 @@ static int si4713_powerup(struct si4713_device
>>> *sdev)
>>> gpio_set_value(sdev->gpio_reset, 1);
>>> }
>>>
>>> + if (client->irq)
>>> + args[0] |= SI4713_PWUP_CTSIEN;
>>> +
>>> err = si4713_send_command(sdev, SI4713_CMD_POWER_UP,
>>> args, ARRAY_SIZE(args),
>>> resp, ARRAY_SIZE(resp),
>>> TIMEOUT_POWER_UP);
>>> -
>>> +
>>
>> Please, do not insert tabulation in blank lines.
>>
>>> if (!err) {
>>> v4l2_dbg(1, debug, &sdev->sd, "Powerup response:
>>> 0x%02x\n",
>>> resp[0]);
>>> v4l2_dbg(1, debug, &sdev->sd, "Device in power up
>>> mode\n");
>>> sdev->power_state = POWER_ON;
>>>
>>> - err = si4713_write_property(sdev, SI4713_GPO_IEN,
>>> + if (client->irq)
>>> + err = si4713_write_property(sdev, SI4713_GPO_IEN,
>>> SI4713_STC_INT |
>>> SI4713_CTS);
>>> } else {
>>> if (gpio_is_valid(sdev->gpio_reset))
>>> @@ -447,7 +461,7 @@ static int si4713_checkrev(struct si4713_device
>>> *sdev)
>>> if (rval < 0)
>>> return rval;
>>>
>>> - if (resp[1] == SI4713_PRODUCT_NUMBER) {
>>> + if (resp[1] == SI4713_PRODUCT_NUMBER) {
>>
>> Please, do not insert spaces in the end of the line.
>>
>>> v4l2_info(&sdev->sd, "chip found @ 0x%02x (%s)\n",
>>> client->addr << 1, client->adapter->name);
>>> } else {
>>> @@ -465,33 +479,34 @@ static int si4713_checkrev(struct si4713_device
>>> *sdev)
>>> */
>>> static int si4713_wait_stc(struct si4713_device *sdev, const int usecs)
>>> {
>>> - int err;
>>> + struct i2c_client *client = v4l2_get_subdevdata(&sdev->sd);
>>> u8 resp[SI4713_GET_STATUS_NRESP];
>>> -
>>> - /* Wait response from STC interrupt */
>>> - if (!wait_for_completion_timeout(&sdev->work,
>>> - usecs_to_jiffies(usecs) + 1))
>>> - v4l2_warn(&sdev->sd,
>>> - "%s: device took too much time to answer (%d
>>> usec).\n",
>>> - __func__, usecs);
>>> -
>>> - /* Clear status bits */
>>> - err = si4713_send_command(sdev, SI4713_CMD_GET_INT_STATUS,
>>> - NULL, 0,
>>> - resp, ARRAY_SIZE(resp),
>>> - DEFAULT_TIMEOUT);
>>> -
>>> - if (err < 0)
>>> - goto exit;
>>> -
>>> - v4l2_dbg(1, debug, &sdev->sd,
>>> - "%s: status bits: 0x%02x\n", __func__, resp[0]);
>>> -
>>> - if (!(resp[0] & SI4713_STC_INT))
>>> - err = -EIO;
>>> -
>>> -exit:
>>> - return err;
>>> + unsigned long start_jiffies = jiffies;
>>> + int err;
>>> +
>>> + if (client->irq &&
>>> + !wait_for_completion_timeout(&sdev->work,
>>> usecs_to_jiffies(usecs) + 1))
>>> + v4l2_warn(&sdev->sd,
>>> + "(%s) Device took too much time to answer.\n",
>>> __func__);
>>> +
>>> + for (;;) {
>>> + /* Clear status bits */
>>> + err = si4713_send_command(sdev, SI4713_CMD_GET_INT_STATUS,
>>> + NULL, 0,
>>> + resp, ARRAY_SIZE(resp),
>>> + DEFAULT_TIMEOUT);
>>> +
>>> + if (err >= 0) {
>>
>> Why are you polling while the command fails? If the command fails, you
>> need to stop, and propagate the error to upper layers. You shall keep
>> polling only while the command succeed and (resp[0] & SI4713_STC_INT)
>> == 0.
>
> This needs a comment. Dinesh, correct me if I am wrong but as I remember
> the usb device actually does return errors when it is waiting for STC.
> It seems the usb device just blocks new usb requests during that wait.
>
> Yes that is right. It does return errors.
>
>
>>
>>> + v4l2_dbg(1, debug, &sdev->sd,
>>> + "%s: status bits: 0x%02x\n",
>>> __func__, resp[0]);
>>> +
>>> + if (resp[0] & SI4713_STC_INT)
>>> + return 0;
>>> + }
>>> + if (jiffies_to_usecs(jiffies - start_jiffies) > usecs)
>>> + return -EIO;
>
> Although this should be replaced with:
>
> return err < 0 ? err : -EIO;
>
>>> + msleep(3);
>>> + }
>>
>> Can you please add a comment why you chose msleep(3)? For instance,
>> here you sleep for 3 ms, in send command you need only 1ms. Any
>> explanation?
>
> Experimentation. If you flood the USB device with USB requests it hangs.
>
> When reverse engineering the Windows USB driver, we also saw ~2.5 ms delay
> between responses. When experimenting with different sleep values, 3 ms
> seemed the
> most appropriate. But you are right, it misses a comment.
>
OK. I got it. And I like the experimentation work done. It is very
good that you got it working by means of reverse engineering.
Jut think that you have tested on, what, 1 board, 1 type of USB
interface? Are you sure this is gonna work on all boards on all cases?
Thus, when adding a magic number in a driver, specially derived from
reverse engineering, it is kind to their users to explain how you
figure out that number. Otherwise, when people start to face issues,
they can look at it from the same perspective you had.
>
>>
>> Besides could you please move this for to another function? Something
>> like si4713_poll_stc?
>
> Why? I see no compelling reason to split it. Some more comments would be
> useful, though.
>
> Regards,
>
> Hans
>
>>
>>> }
>>>
>>> /*
>>> @@ -1024,7 +1039,6 @@ static int si4713_initialize(struct si4713_device
>>> *sdev)
>>> if (rval < 0)
>>> return rval;
>>>
>>> -
>>> sdev->frequency = DEFAULT_FREQUENCY;
>>> sdev->stereo = 1;
>>> sdev->tune_rnl = DEFAULT_TUNE_RNL;
>>> diff --git a/drivers/media/radio/si4713/si4713.h
>>> b/drivers/media/radio/si4713/si4713.h
>>> index c274e1f..dc0ce66 100644
>>> --- a/drivers/media/radio/si4713/si4713.h
>>> +++ b/drivers/media/radio/si4713/si4713.h
>>> @@ -15,6 +15,7 @@
>>> #ifndef SI4713_I2C_H
>>> #define SI4713_I2C_H
>>>
>>> +#include <linux/regulator/consumer.h>
>>> #include <media/v4l2-subdev.h>
>>> #include <media/v4l2-ctrls.h>
>>> #include <media/si4713.h>
>>> --
>>> 1.8.4.rc2
>>>
>>> --
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>>
>>
>>
>>
>
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>
--
Eduardo Bezerra Valentin
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