hollalinux
/
linux-sg2042
mirror of https://github.com/sophgo/linux-riscv.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

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>
This commit is contained in:
Jonathan Corbet 2007-08-17 01:02:33 -03:00 committed by Mauro Carvalho Chehab
parent 01659f2a00
commit 6d77444aca
2 changed files with 25 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
drivers/media/video/cafe_ccic.c
View File

@ -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);

5
drivers/media/video/ov7670.c
View File

@ -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;
}