Re: [PATCH 3/6] board: ti: am62x: Add basic initialization for usb voltage, 32k crystal, debounce

[Francesco Dolcini <francesco@dolcini.it>]

On Tue, Jul 25, 2023 at 05:03:28PM -0500, Nishanth Menon wrote:
> On 17:42-20230725, Tom Rini wrote:
> > On Tue, Jul 25, 2023 at 04:37:55PM -0500, Nishanth Menon wrote:
> > > On 17:25-20230725, Tom Rini wrote:
> > > > On Tue, Jul 25, 2023 at 01:52:50PM -0500, Nishanth Menon wrote:
> > > [..]
> > > 
> > > > > +	/* Set USB0 PHY core voltage to 0.85V */
> > > > > +	val = readl(CTRLMMR_USB0_PHY_CTRL);
> > > > > +	val &= ~(CORE_VOLTAGE);
> > > > > +	writel(val, CTRLMMR_USB0_PHY_CTRL);
> > > > > +
> > > > > +	/* Set USB1 PHY core voltage to 0.85V */
> > > > > +	val = readl(CTRLMMR_USB1_PHY_CTRL);
> > > > > +	val &= ~(CORE_VOLTAGE);
> > > > > +	writel(val, CTRLMMR_USB1_PHY_CTRL);
> > > > > +
> > > > > +	/* We have 32k crystal, so lets enable it */
> > > > > +	val = readl(MCU_CTRL_LFXOSC_CTRL);
> > > > > +	val &= ~(MCU_CTRL_LFXOSC_32K_DISABLE_VAL);
> > > > > +	writel(val, MCU_CTRL_LFXOSC_CTRL);
> > > > > +	/* Add any TRIM needed for the crystal here.. */
> > > > > +	/* Make sure to mux up to take the SoC 32k from the crystal */
> > > > > +	writel(MCU_CTRL_DEVICE_CLKOUT_LFOSC_SELECT_VAL,
> > > > > +	       MCU_CTRL_DEVICE_CLKOUT_32K_CTRL);
> > > > > +
> > > > > +	/* Setup debounce conf registers - arbitrary values. Times are approx */
> > > > > +	/* 1.9ms debounce @ 32k */
> > > > > +	writel(WKUP_CTRLMMR_DBOUNCE_CFG1, 0x1);
> > > > > +	/* 5ms debounce @ 32k */
> > > > > +	writel(WKUP_CTRLMMR_DBOUNCE_CFG2, 0x5);
> > > > > +	/* 20ms debounce @ 32k */
> > > > > +	writel(WKUP_CTRLMMR_DBOUNCE_CFG3, 0x14);
> > > > > +	/* 46ms debounce @ 32k */
> > > > > +	writel(WKUP_CTRLMMR_DBOUNCE_CFG4, 0x18);
> > > > > +	/* 100ms debounce @ 32k */
> > > > > +	writel(WKUP_CTRLMMR_DBOUNCE_CFG5, 0x1c);
> > > > > +	/* 156ms debounce @ 32k */
> > > > > +	writel(WKUP_CTRLMMR_DBOUNCE_CFG6, 0x1f);
> > > > > +
> > > > >  	video_setup();
> > > > >  	enable_caches();
> > > > >  	if (IS_ENABLED(CONFIG_SPL_SPLASH_SCREEN) && IS_ENABLED(CONFIG_SPL_BMP))
> > > > 
> > > > Here's a whole lot of seemingly board specific code in a function and
> > > > file that's supposed to support any am62 platform. Is this really what
> > > > we need, where we need it?
> > > 
> > > * without using the correct voltage for USB, we risk damaging the IOs -
> > >   board specific, sure.
> > 
> > So what happens when we do this on the other EVM, does it have the same
> > values? Is there some must-always-be-safe values? Or is the answer "we
> > must do this board specific to be safe" and so need to re-think what can
> > and can't be shared between board builds.
> 
> At least the ones we have currently (I am not sure about toradex,
> phytech etc), seem to operate the vdd_core at 0.85V .. (which is what
> USB is dependent upon).

For Toradex, we do have the equivalent code in our board file, see 
https://git.toradex.com/cgit/u-boot-toradex.git/tree/board/toradex/verdin-am62/verdin-am62.c?h=toradex_ti-u-boot-2023.04#n92

The 32kHz configuration is just different for us, we do not re-use the
same you have here.

The debounce conf registers I have no idea what they are about,
something we should have also on our board? Any additional details?

Francesco