Re: [PATCH] ARM: OMAP2+: pm34xx: add NEON wakeup dependency before clockdomain idle

[Andreas Kemnade <andreas@kemnade.info>]

On Fri, 13 Nov 2026 10:11:05 -0800
"Kevin Hilman (TI)" <khilman@baylibre.com> wrote:

> On OMAP3630 (BeagleBoard-xM), about one boot in three dies early when
> a context switch touches the VFP, which traps as undefined.
> 
> The VFP is unreachable because NEON is powered off while the MPU runs.
> omap3_pm_init() sets NEON's next state to OFF/RET and lets all
> clockdomains idle before it adds the NEON -> MPU wakeup dependency, so
> NEON can power down immediately and stay off until the MPU next idles.
> This was visible in pm_debug, which showed neon_pwrdm OFF:1 while
> mpu_pwrdm OFF:0.
> 
> Add the wakeup dependency before the clockdomains are allowed to idle.
> 
> Tested on omap3-beagle-xm: 6/17 boots crashed before, none of 25 after;
> also ran 50 suspend/resume cycles each on omap3-beagle and -xm.
> 
> Fixes: fa3c2a4fc99f ("OMAP3: PM: handle PER/NEON/CORE in idle")
> Reported-by: Andreas Kemnade <andreas@kemnade.info>
> Closes: https://lore.kernel.org/r/20261028212302.75ec622e@kemnade.info
> Signed-off-by: Kevin Hilman (TI) <khilman@baylibre.com>

survived a git bisect + several other boots on GTA04. (tested the identical
change in a comment before)

Tested-by: Andreas Kemnade <andreas@kemnade.info> # GTA04
> ---
> This patch combined with an omap_device fix from Andreas makes OMAP3
> very stable on suspend/resume, including off-mode for OMAP3630.
> c.f. https://lore.kernel.org/r/20261110211531.679943-1-andreas@kemnade.info
> ---
>  arch/arm/mach-omap2/pm34xx.c | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/mach-omap2/pm34xx.c b/arch/arm/mach-omap2/pm34xx.c
> index 9992549c7336..d11967c2f4bf 100644
> --- a/arch/arm/mach-omap2/pm34xx.c
> +++ b/arch/arm/mach-omap2/pm34xx.c
> @@ -510,6 +510,20 @@ int __init omap3_pm_init(void)
>  		goto err3;
>  	}
>  
> +	neon_clkdm = clkdm_lookup("neon_clkdm");
> +	mpu_clkdm = clkdm_lookup("mpu_clkdm");
> +	per_clkdm = clkdm_lookup("per_clkdm");
> +	wkup_clkdm = clkdm_lookup("wkup_clkdm");
> +
> +	/*
> +	 * Add the NEON wakeup dependency on the MPU before the clockdomains
> +	 * are allowed to idle: once pwrdms_setup() has programmed NEON's next
> +	 * state to OFF/RET, an idle NEON clockdomain otherwise lets NEON power
> +	 * down while the MPU keeps running, and VFP instructions then trap as
> +	 * undefined until NEON is woken.
> +	 */
> +	clkdm_add_wkdep(neon_clkdm, mpu_clkdm);
> +
>  	(void) clkdm_for_each(omap_pm_clkdms_setup, NULL);
>  
>  	mpu_pwrdm = pwrdm_lookup("mpu_pwrdm");
> @@ -523,11 +537,6 @@ int __init omap3_pm_init(void)
>  	per_pwrdm = pwrdm_lookup("per_pwrdm");
>  	core_pwrdm = pwrdm_lookup("core_pwrdm");
>  
> -	neon_clkdm = clkdm_lookup("neon_clkdm");
> -	mpu_clkdm = clkdm_lookup("mpu_clkdm");
> -	per_clkdm = clkdm_lookup("per_clkdm");
> -	wkup_clkdm = clkdm_lookup("wkup_clkdm");
> -
>  	omap_common_suspend_init(omap3_pm_suspend);
>  
>  	arm_pm_idle = omap3_pm_idle;
> @@ -562,7 +571,6 @@ int __init omap3_pm_init(void)
>  	if (IS_PM34XX_ERRATUM(PM_PER_MEMORIES_ERRATUM_i582))
>  		clkdm_add_wkdep(per_clkdm, wkup_clkdm);
>  
> -	clkdm_add_wkdep(neon_clkdm, mpu_clkdm);
>  	if (omap_type() != OMAP2_DEVICE_TYPE_GP) {
>  		omap3_secure_ram_storage =
>  			kmalloc(OMAP3_SAVE_SECURE_RAM_SZ, GFP_KERNEL);
> 
> ---
> base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
> change-id: 20261113-wip-omap3-vfp-neon-mismatch-ae585c1e8fe0
> 
> Best regards,
> --  
> Kevin Hilman (TI) <khilman@baylibre.com>
> 
>