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[35.187.245.222]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a88b4c3d2bsm161078895ad.53.2026.02.02.12.14.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Feb 2026 12:14:31 -0800 (PST) Date: Mon, 2 Feb 2026 20:14:26 +0000 From: Pranjal Shrivastava To: Robin Murphy Cc: Prakash Gupta , Will Deacon , Joerg Roedel , Rob Clark , Connor Abbott , linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, Akhil P Oommen , Pratyush Brahma Subject: Re: [PATCH] iommu/arm-smmu: Use pm_runtime in fault handlers Message-ID: References: <20260127-smmu-rpm-v1-1-2ef2f4c85305@oss.qualcomm.com> <9fb8f661-a235-4f86-bc10-f80a21a8fa9d@arm.com> <00fcbcf2-3f48-410d-88a3-88dc834c1ed7@oss.qualcomm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Jan 28, 2026 at 06:44:35PM +0000, Robin Murphy wrote: > [ +Pranjal as this might matter for v3 too... ] > Hi Robin, To weigh in from the arm-smmu-v3 side, we’ve attempted to address the "can of worms" regarding power races by leaning on these differences: - Threaded IRQs for PRI/Events: In the recent series[1], the PRI and event handlers are fully threaded. This allows us to call arm_smmu_rpm_get() safely, as the handler can sleep while waiting for the hardware to resume. - GERROR Handling: Since GERROR remains a hard IRQ, we handle any pending gerrors in the suspend callback before the SMMU actually powers down. Any GERROR interrupts received while the device was suspended are treated as spurious and ignored. Thanks, Praan [1] https://lore.kernel.org/all/20260126151157.3418145-1-praan@google.com/ [...] > > Hmm, but then how *do* we actually guarantee that autosuspend doesn't happen > to kick in and power down the SMMU just as a hardirq handler runs, when > there's some unexpected event? I fear there's a horrible can of worms > here... > > Thanks, > Robin.