Re: [PATCH] I2C: i.MX: early: Use internal udelay

[John Watts <contact@jookia.org>]

On Mon, Jan 30, 2023 at 01:17:52PM +0100, Sascha Hauer wrote:
> On Mon, Jan 30, 2023 at 09:42:53PM +1100, John Watts wrote:
> > On Mon, Jan 30, 2023 at 11:27:27AM +0100, Sascha Hauer wrote:
> > > This takes around 5 times too long on a i.MX8MM and around 50 times too
> > > long on a i.MX6Q. This was measured under a regular barebox on the
> > > shell. In an early environment with MMU disabled it takes 730 times too
> > > long.
> > 
> > Yikes! I'm glad I broke this in to its own patch then. :)
> > 
> > I did copy this code from these boards:
> > 
> > arch/arm/boards/cm-fx6/lowlevel.c
> > arch/arm/boards/skov-imx6/lowlevel.c
> > arch/arm/boards/technexion-wandboard/lowlevel.c
> > arch/arm/mach-imx/xload-gpmi-nand.c
> > arch/arm/mach-imx/imx6-mmdc.c (uses 1000 loops)
> > 
> > Maybe it's time for an i.MX6-wide early udelay?
> 
> i.MX6 is not enough, the code could run on other i.MX SoCs as well.

Do you think a patch that implements udelay in PBL using the code below with
a fixed base and drops these implementations would be a good idea?

> I tested this with a call to this udelay function with a sufficiently
> great number of microseconds surrounded by a printf.

Ah okay.

> I briefly looked into this, but the commit history of both barebox or
> Linux do not give a real conclusion what we are waiting here for.
> 
> Sascha

I see.

John.