On Mon, 27 Oct 2008 17:07:05 +0300, Sergei Shtylyov <sshtylyov@xxxxxxxxxxxxx> wrote:
> > + /* -DIOx recovery time (SHWT * 4) and cycle time requirement */
> > + while (shwt * cycle * 4 + t->act8b < t->cycle)
>
> This can lead to adding an extra setup cycle due to use of "non-quantized"
> active time, here's more precise expression for the cycle time:
>
> (shwt * 4 + wt + (wt ? 2 : 3)) * cycle
>
> or even this, more obsure:
>
> (shwt * 4 + wt + !wt + 2) * cycle
Hm, indeed. I prefer former one. Revised. Thanks!
From: Atsushi Nemoto <anemo@xxxxxxxxxxxxx>
Subject: [PATCH] tx4938ide: Check minimum cycle time and SHWT range (v2)
SHWT value is used as address valid to -CSx assertion and -CSx to -DIOx
assertion setup time, and contrarywise, -DIOx to -CSx release and -CSx
release to address invalid hold time, so it actualy applies 4 times and
so constitutes -DIOx recovery time. Check requirement of the recovery
time and cycle time. Also check SHWT maximum value.
Suggested-by: Sergei Shtylyov <sshtylyov@xxxxxxxxxxxxx>
Signed-off-by: Atsushi Nemoto <anemo@xxxxxxxxxxxxx>
---
drivers/ide/tx4938ide.c | 9 ++++++++-
1 files changed, 8 insertions(+), 1 deletions(-)
diff --git a/drivers/ide/tx4938ide.c b/drivers/ide/tx4938ide.c
index a0d10a9..796289c 100644
--- a/drivers/ide/tx4938ide.c
+++ b/drivers/ide/tx4938ide.c
@@ -39,10 +39,17 @@ static void tx4938ide_tune_ebusc(unsigned int ebus_ch,
/* Address-valid to DIOR/DIOW setup */
shwt = DIV_ROUND_UP(t->setup, cycle);
+ /* -DIOx recovery time (SHWT * 4) and cycle time requirement */
+ while ((shwt * 4 + wt + (wt ? 2 : 3)) * cycle < t->cycle)
+ shwt++;
+ if (shwt > 7) {
+ pr_warning("tx4938ide: SHWT violation (%d)\n", shwt);
+ shwt = 7;
+ }
pr_debug("tx4938ide: ebus %d, bus cycle %dns, WT %d, SHWT %d\n",
ebus_ch, cycle, wt, shwt);
- __raw_writeq((cr & ~(0x3f007ull)) | (wt << 12) | shwt,
+ __raw_writeq((cr & ~0x3f007ull) | (wt << 12) | shwt,
&tx4938_ebuscptr->cr[ebus_ch]);
}
--
1.5.6.3
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