On Fri, Sep 14, 2012 at 11:29:06AM +0200, Dirk Behme wrote:
> On 12.09.2012 12:31, Sascha Hauer wrote:
> >+
> >+ timeout = jiffies + msecs_to_jiffies(1000);
> >+ while (ipu_cm_read(ipu, IPU_MEM_RST) & 0x80000000) {
> >+ if (time_after(jiffies, timeout))
> >+ return -ETIME;
> >+ cpu_relax();
> >+ }
> >+
> >+ mdelay(300);
> ^^^^^^^^^^^^
>
> >+ return 0;
> >+}
>
> While doing some boot time measurement with i.MX6, we found that the
> above mdelay(300) is hurting regarding boot time. On i.MX6 you have
> two IPU instances, so in the end you get 600ms additional delay.
>
> Looking at the Freescale code, this function looks like
>
> static int ipu_reset(struct ipu_soc *ipu)
> {
> int timeout = 1000;
>
> ipu_cm_write(ipu, 0x807FFFFF, IPU_MEM_RST);
>
> while (ipu_cm_read(ipu, IPU_MEM_RST) & 0x80000000) {
> if (!timeout--)
> return -ETIME;
> msleep(1);
> }
> return 0;
> }
>
> So there is a msleep() in the loop but no mdelay() outside. Any idea
> why the mdelay() is needed here? Or what could be done regarding
> boot time with this?
I remember we had issues on i.MX51 or 53 without it, but I would have to
recheck it.
In any way, I think this should be reworked. The reset takes quite a
long time and it's not nice to block the boot process for so long.
Some asynchronous reset would be nice here.
Sascha
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