Robert Schedel wrote:
> Robert Schedel wrote:
>
> > Is the 250ms timeout an approved limit? Decreasing it would push the
> > load further down. Probably it still has to cover slow CAMs as well as a
> > stressed PCI bus. Unfortunately, without CAM/CI I cannot make any
> > statements myself.
>
> Just got another idea to improve the code: Function
> "saa7146_wait_for_debi_done_sleep" could be reworked to use what is
> known as "truncated binary exponential backoff" algorithm. IOW, on each
> sleep duplicate the period from 1ms until a fixed maximum, e.g. 32ms.
> This way polling ends fast for those users with fast bus/CAM, and those
> requiring 200ms due to slow bus/CAM should not worry about e.g. 216ms
> response time.
>
> My first tests look promising (load goes down to 0). However, is not the
> simple BEB algorithm already patented?
Load should go down to 0 if the sleep call does not busy-wait.
Please test whether the attached code fixes the problem.
Btw, I will not claim a patent for that. :D
CU
Oliver
--
----------------------------------------------------------------
VDR Remote Plugin 0.4.0: http://www.escape-edv.de/endriss/vdr/
----------------------------------------------------------------
diff -r f500c56d9064 linux/drivers/media/common/saa7146_core.c
--- a/linux/drivers/media/common/saa7146_core.c Fri Apr 11 11:22:15 2008 +0200
+++ b/linux/drivers/media/common/saa7146_core.c Fri Apr 18 02:25:39 2008 +0200
@@ -64,8 +64,10 @@ static inline int saa7146_wait_for_debi_
{
unsigned long timeout;
int err;
+ bool slow;
/* wait for registers to be programmed */
+ slow = false;
timeout = jiffies + usecs_to_jiffies(us1);
while (1) {
err = time_after(jiffies, timeout);
@@ -77,10 +79,12 @@ static inline int saa7146_wait_for_debi_
dev->name, __func__);
return -ETIMEDOUT;
}
- msleep(1);
+ msleep(slow ? 10 : 1);
+ slow = true;
}
/* wait for transfer to complete */
+ slow = false;
timeout = jiffies + usecs_to_jiffies(us2);
while (1) {
err = time_after(jiffies, timeout);
@@ -92,7 +96,8 @@ static inline int saa7146_wait_for_debi_
"completion\n", dev->name, __func__));
return -ETIMEDOUT;
}
- msleep(1);
+ msleep(slow ? 10 : 1);
+ slow = true;
}
return 0;
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