Re: [PATCH 3/4] i2c: imx: add macros and printk to make debug easy

Richard Zhao
2009-10-01T09:30:48Z

On Thu, Oct 1, 2009 at 4:26 PM, Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> wrote:
> On Thu, Oct 01, 2009 at 04:01:50PM +0800, Richard Zhao wrote:
>> On Thu, Oct 1, 2009 at 3:29 PM, Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> wrote:
>> > On Thu, Oct 01, 2009 at 09:13:32AM +0800, Richard Zhao wrote:
>> >> When CONFIG_I2C_DEBUG_BUS is enabled, it helps dump registers at operation
>> >> fail condition, and print i2c_msg to xfer.
>> >>
>> >> Signed-off-by: Richard Zhao <linuxzsc-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> >
>> > Honestly I don't think we need this. It makes the driver too verbose for
>> > my taste.
>> >
>> > Sascha
>> >
>> >
>> >>
>> >> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
>> >> index c1e541c..87faea4 100644
>> >> --- a/drivers/i2c/busses/i2c-imx.c
>> >> +++ b/drivers/i2c/busses/i2c-imx.c
>> >> @@ -125,6 +125,20 @@ struct imx_i2c_struct {
>> >>  /** Functions for IMX I2C adapter driver ***************************************
>> >>  *******************************************************************************/
>> >>
>> >> +#ifdef CONFIG_I2C_DEBUG_BUS
>> >> +#define reg_dump(i2c_imx) \
>> >> +{ \
>> >> +     printk(KERN_DEBUG "fun %s:%d ", __func__, __LINE__); \
>> >> +     printk(KERN_DEBUG "IADR %02x IFDR %02x I2CR %02x I2SR %02x\n", \
>> >> +             readb(i2c_imx->base + IMX_I2C_IADR), \
>> >> +             readb(i2c_imx->base + IMX_I2C_IFDR), \
>> >> +             readb(i2c_imx->base + IMX_I2C_I2CR), \
>> >> +             readb(i2c_imx->base + IMX_I2C_I2SR)); \
>> >> +}
>> >> +#else
>> >> +#define reg_dump(i2c_imx)
>> >> +#endif
>> >> +
>> >>  static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy)
>> >>  {
>> >>       unsigned long orig_jiffies = jiffies;
>> >> @@ -146,6 +160,7 @@ static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy)
>> >>               if (time_after(jiffies, orig_jiffies + HZ / 1000)) {
>> >>                       dev_dbg(&i2c_imx->adapter.dev,
>> >>                               "<%s> I2C bus is busy\n", __func__);
>> >> +                     reg_dump(i2c_imx);
>> >>                       return -EIO;
>> >>               }
>> >>               schedule();
>> >> @@ -164,9 +179,11 @@ static int i2c_imx_trx_complete(struct imx_i2c_struct *i2c_imx)
>> >>
>> >>       if (unlikely(result < 0)) {
>> >>               dev_dbg(&i2c_imx->adapter.dev, "<%s> result < 0\n", __func__);
>> >> +             reg_dump(i2c_imx);
>> >>               return result;
>> >>       } else if (unlikely(!(i2c_imx->i2csr & I2SR_IIF))) {
>> >>               dev_dbg(&i2c_imx->adapter.dev, "<%s> Timeout\n", __func__);
>> >> +             reg_dump(i2c_imx);
>> >>               return -ETIMEDOUT;
>> >>       }
>> >>       dev_dbg(&i2c_imx->adapter.dev, "<%s> TRX complete\n", __func__);
>> >> @@ -178,6 +195,7 @@ static int i2c_imx_acked(struct imx_i2c_struct *i2c_imx)
>> >>  {
>> >>       if (readb(i2c_imx->base + IMX_I2C_I2SR) & I2SR_RXAK) {
>> >>               dev_dbg(&i2c_imx->adapter.dev, "<%s> No ACK\n", __func__);
>> >> +             reg_dump(i2c_imx);
>> >>               return -EIO;  /* No ACK */
>> >>       }
>> >>
>> >> @@ -197,17 +215,20 @@ static int i2c_imx_start(struct imx_i2c_struct *i2c_imx)
>> >>       writeb(I2CR_IEN, i2c_imx->base + IMX_I2C_I2CR);
>> >>
>> >>       result = i2c_imx_bus_busy(i2c_imx, 0);
>> >> -     if (result)
>> >> +     if (result) {
>> >> +             reg_dump(i2c_imx);
>> >>               return result;
>> >> +     }
>> >>
>> >>       /* Start I2C transaction */
>> >>       temp = readb(i2c_imx->base + IMX_I2C_I2CR);
>> >>       temp |= I2CR_MSTA;
>> >>       writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
>> >>       result = i2c_imx_bus_busy(i2c_imx, 1);
>> >> -     if (result)
>> >> +     if (result) {
>> >> +             reg_dump(i2c_imx);
>> >>               return result;
>> >> -
>> >> +     }
>> >>       temp |= I2CR_IIEN | I2CR_MTX | I2CR_TXAK;
>> >>       writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
>> >>       return result;
>> >> @@ -228,7 +249,8 @@ static void i2c_imx_stop(struct imx_i2c_struct *i2c_imx)
>> >>        */
>> >>       udelay(i2c_imx->disable_delay);
>> >>
>> >> -     i2c_imx_bus_busy(i2c_imx, 0);
>> >> +     if (i2c_imx_bus_busy(i2c_imx, 0))
>> >> +             reg_dump(i2c_imx);
>> >>
>> >>       /* Disable I2C controller */
>> >>       writeb(0, i2c_imx->base + IMX_I2C_I2CR);
>> >> @@ -389,7 +411,18 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
>> >>       struct imx_i2c_struct *i2c_imx = i2c_get_adapdata(adapter);
>> >>
>> >>       dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
>> >> -
>> >> +#ifdef CONFIG_I2C_DEBUG_BUS
>> >> +     for (i = 0; i < num; i++) {
>> >> +             printk(KERN_DEBUG "msg%d addr %02x RD %d cnt %d d:", i,
>> >> +                     msgs[i].addr, msgs[i].flags & I2C_M_RD, msgs[i].len);
>> >> +             if (!(msgs[i].flags & I2C_M_RD)) {
>> >> +                     int j;
>> >> +                     for (j = 0; j < msgs[i].len; j++)
>> >> +                             printk("%02x ", msgs[i].buf[j]);
>> >> +             }
>> >> +             printk("\n");
>> >> +     }
>> >> +#endif
>> >>       /* Start I2C transfer */
>> >>       result = i2c_imx_start(i2c_imx);
>> >>       if (result)
>> >> @@ -404,8 +437,10 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
>> >>                       temp |= I2CR_RSTA;
>> >>                       writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
>> >>                       result =  i2c_imx_bus_busy(i2c_imx, 1);
>> >> -                     if (result)
>> >> +                     if (result) {
>> >> +                             reg_dump(i2c_imx);
>> >>                               goto fail0;
>> >> +                     }
>> >>               }
>> >>               dev_dbg(&i2c_imx->adapter.dev,
>> >>                       "<%s> transfer message: %d\n", __func__, i);
>> >> @@ -562,7 +597,7 @@ static int __init i2c_imx_probe(struct platform_device *pdev)
>> >>               res_size, i2c_imx->res->start);
>> >>       dev_dbg(&i2c_imx->adapter.dev, "adapter name: \"%s\"\n",
>> >>               i2c_imx->adapter.name);
>> >> -     dev_dbg(&i2c_imx->adapter.dev, "IMX I2C adapter registered\n");
>> >> +     dev_info(&i2c_imx->adapter.dev, "IMX I2C adapter registered\n");
>> >>
>> >>       return 0;   /* Return OK */
>> >>
>> >> --
>> >> 1.6.0.4
>> >>
>> >>
>> >
>> > --
>> > Pengutronix e.K.                           |                             |
>> > Industrial Linux Solutions                 | http://www.pengutronix.de/  |
>> > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
>> > Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
>> >
>>
>> 1. i2c is more important bus in embedded system than PC. Many PMICs
>> are connected to cpu via i2c. Before system boot up, we depend much on
>> printk message.
>> 2. When we add a new i2c device, it's easy to have problems. Maybe
>> it's hw issue, one device fails, all ones in the same bus fails. In
>> such condition, debug message is very helpfull.
>
> The driver already consists to 15% of debug statements, there is
> definitely no need to add even more. If anything, you could concentrate
> on making the output more useful.
The dump_reg are only added when operation fails. It's not used to
track function call path or anything else.
I'm not supposed to show detailed message when there's operation fail?
The reason to add a switch to disable it is, when i2c tools scan the
bus, it will cause operation fail.

Richard
>
> Sascha
>
> --
> Pengutronix e.K.                           |                             |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
> Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
> Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
>