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Tue, 10 Nov 2026 11:48:48 -0800 (PST) From: Kevin Hilman To: Andreas Kemnade , Aaro Koskinen , Roger Quadros , Tony Lindgren , Russell King Cc: linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, absicsz@gmail.com Subject: Re: [PATCH 1/2] ARM: omap: cpuidle34xx: balance cpu_pm_enter/exit() In-Reply-To: <20261028212302.75ec622e@kemnade.info> References: <20261028-susp2-v1-0-174b52857d89@kemnade.info> <20261028-susp2-v1-1-174b52857d89@kemnade.info> <20261028212302.75ec622e@kemnade.info> Date: Tue, 10 Nov 2026 11:48:47 -0800 Message-ID: <7ha4ngv55s.fsf@baylibre.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261110_114850_513280_53396C81 X-CRM114-Status: GOOD ( 19.91 ) X-Spam-Score: -2.1 (--) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" X-Spam-Status: No, score=-15.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Andreas Kemnade writes: > On Wed, 28 Oct 2026 20:15:11 +0100 > Andreas Kemnade wrote: > >> These calls are usually done in a balanced way, so allow notifiers to >> assume that these calls are balanced under all circumstances. >> Seen some spurios vfp issues probably connected to this. >> >> Signed-off-by: Andreas Kemnade > > Looked again at some discussions with Sicelo testing such things: > He had observed a NEON off count 1 but MPU 0 in /sys/kernel/debug/pm_debug/count. > Probably more involved, but lets not freak out things here. > So that is definitively a real problem fixed by this. vfp_pm_resume() > would not be called to restore the state without a patch like this. > > So this is > > Fixes: 1cd96478cf150 ("ARM: OMAP3xxx: CPUIdle: optimize __omap3_enter_idle()") Even with this fix, I found on OMAP3 (beagle and beagle-xm) that there are still intermittent failures, and the NEON vs. MPU count mismatch was a good indicator to dig a little deeper. I think the fix here is to add the neon_clkdm -> mpu_clkdm wakeup dependency before the clockdomains are allowed to idle. Otherwise NEON could idle immediately. With the patch below, I don't see any intermittent VFP crashes anymore with early testing. I'm still doing a few more tests, but will sent a proper patch with changelog after some more testing. Kevin 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);