| Message ID | 1366654990-15392-1-git-send-email-mikedunn@newsguy.com |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, 2013-04-22 at 11:23 -0700, Mike Dunn wrote: > timeo = 1000; > do { > + udelay(1); > cpu_relax(); > flash_status = readb(docptr + DOC_FLASHCONTROL); > } while (!(flash_status & DOC_CTRL_FLASHREADY) && --timeo); How about using jiffies instead? Something like: timeout = jiffies + msecs_to_jiffies(delay); do { } while (time_before(jiffies, timeout))
On 05/16/2013 12:43 AM, Artem Bityutskiy wrote: > On Mon, 2013-04-22 at 11:23 -0700, Mike Dunn wrote: >> timeo = 1000; >> do { >> + udelay(1); >> cpu_relax(); >> flash_status = readb(docptr + DOC_FLASHCONTROL); >> } while (!(flash_status & DOC_CTRL_FLASHREADY) && --timeo); > > How about using jiffies instead? Something like: > > timeout = jiffies + msecs_to_jiffies(delay); > do { > } while (time_before(jiffies, timeout)) > This works too (just tested it). But the reason I did not do this originally is because the timeout is very short. With udelay(1) and timeo=1000, the timeout is 1ms (plus processing time), and I think this is well in excess of the actual time needed by the hardware. Using jiffies and with HZ=100, my minimum timeout is 10ms. But there's no harm in having an excessive timeout since it's a busy-wait loop, so your suggestion is probably fine. Is use of udelay() frowned upon? Will using jiffies cause a problem with a "tickless" configuration? Hoping to learn something... Thanks Artem! Mike
diff --git a/drivers/mtd/nand/docg4.c b/drivers/mtd/nand/docg4.c index 18fa448..fd353d2 100644 --- a/drivers/mtd/nand/docg4.c +++ b/drivers/mtd/nand/docg4.c @@ -279,6 +279,7 @@ static int poll_status(struct docg4_priv *doc) timeo = 1000; do { + udelay(1); cpu_relax(); flash_status = readb(docptr + DOC_FLASHCONTROL); } while (!(flash_status & DOC_CTRL_FLASHREADY) && --timeo);
Add call to udelay(1) in the busy-wait loop that polls the device status register. This will make the timeout independent of cpu clock rate. This sloppiness came back to bite me when I increased the cpu clock rate, and timeouts started occurring during long block erasure operations. Signed-off-by: Mike Dunn <mikedunn@newsguy.com> --- drivers/mtd/nand/docg4.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-)