diff options
| author | Jonathan Corbet <corbet@lwn.net> | 2007-08-17 08:02:33 +0400 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@infradead.org> | 2007-08-20 19:18:04 +0400 |
| commit | 6d77444aca298b43a88086be446f943cd0442ef7 (patch) | |
| tree | 3d0b4c4834fcd1048e4f80c5f60847efbe102fdf /drivers | |
| parent | 01659f2a0067d855089811529fa596cbc40f1e75 (diff) | |
| download | linux-6d77444aca298b43a88086be446f943cd0442ef7.tar.xz | |
V4L/DVB (6027): Get rid of an ill-behaved msleep in i2c write
Configuring the OLPC camera requires something over 150 register
writes. Unfortunately, querying the CAFE i2c controller too
soon after a write causes the hardware to flake. The problem had
been "solved" with an msleep() call, but, between the number of
registers and how msleep() behaves, that resulted in a 3-second
delay on camera initialization. Instead, we hand-code a wait for
the completion interrupt which avoids reading the status registers.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/media/video/cafe_ccic.c | 22 | ||||
| -rw-r--r-- | drivers/media/video/ov7670.c | 5 |
2 files changed, 25 insertions, 2 deletions
diff --git a/drivers/media/video/cafe_ccic.c b/drivers/media/video/cafe_ccic.c index 88090107cd44..acf64b19730e 100644 --- a/drivers/media/video/cafe_ccic.c +++ b/drivers/media/video/cafe_ccic.c @@ -356,6 +356,7 @@ static int cafe_smbus_write_data(struct cafe_camera *cam, { unsigned int rval; unsigned long flags; + DEFINE_WAIT(the_wait); spin_lock_irqsave(&cam->dev_lock, flags); rval = TWSIC0_EN | ((addr << TWSIC0_SID_SHIFT) & TWSIC0_SID); @@ -369,10 +370,29 @@ static int cafe_smbus_write_data(struct cafe_camera *cam, rval = value | ((command << TWSIC1_ADDR_SHIFT) & TWSIC1_ADDR); cafe_reg_write(cam, REG_TWSIC1, rval); spin_unlock_irqrestore(&cam->dev_lock, flags); - msleep(2); /* Required or things flake */ + /* + * Time to wait for the write to complete. THIS IS A RACY + * WAY TO DO IT, but the sad fact is that reading the TWSIC1 + * register too quickly after starting the operation sends + * the device into a place that may be kinder and better, but + * which is absolutely useless for controlling the sensor. In + * practice we have plenty of time to get into our sleep state + * before the interrupt hits, and the worst case is that we + * time out and then see that things completed, so this seems + * the best way for now. + */ + do { + prepare_to_wait(&cam->smbus_wait, &the_wait, + TASK_UNINTERRUPTIBLE); + schedule_timeout(1); /* even 1 jiffy is too long */ + finish_wait(&cam->smbus_wait, &the_wait); + } while (!cafe_smbus_write_done(cam)); + +#ifdef IF_THE_CAFE_HARDWARE_WORKED_RIGHT wait_event_timeout(cam->smbus_wait, cafe_smbus_write_done(cam), CAFE_SMBUS_TIMEOUT); +#endif spin_lock_irqsave(&cam->dev_lock, flags); rval = cafe_reg_read(cam, REG_TWSIC1); spin_unlock_irqrestore(&cam->dev_lock, flags); diff --git a/drivers/media/video/ov7670.c b/drivers/media/video/ov7670.c index f8f21ddd9843..c4c5bd67f795 100644 --- a/drivers/media/video/ov7670.c +++ b/drivers/media/video/ov7670.c @@ -416,7 +416,10 @@ static int ov7670_read(struct i2c_client *c, unsigned char reg, static int ov7670_write(struct i2c_client *c, unsigned char reg, unsigned char value) { - return i2c_smbus_write_byte_data(c, reg, value); + int ret = i2c_smbus_write_byte_data(c, reg, value); + if (reg == REG_COM7 && (value & COM7_RESET)) + msleep(2); /* Wait for reset to run */ + return ret; } |