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([2001:8a0:d6cd:9000:86f4:4e71:9fc8:3183]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-499aa17f202sm75178105e9.13.2026.08.19.12.22.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Aug 2026 12:22:28 -0700 (PDT) Message-ID: <45a31ea4-7660-44c6-980e-daec6655629e@reactivated.net> Date: Wed, 19 Aug 2026 20:22:26 +0100 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/5] iommu: Add Broadcom BCM2712 IOMMU driver To: Jim Quinlan Cc: bcm-kernel-feedback-list@broadcom.com, conor+dt@kernel.org, devicetree@vger.kernel.org, florian.fainelli@broadcom.com, iommu@lists.linux.dev, jgg@ziepe.ca, joro@8bytes.org, krzk+dt@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, nick.hollinghurst@raspberrypi.com, robh@kernel.org, robin.murphy@arm.com, will@kernel.org References: <20260727-bcm2712-iommu-submit-v2-0-0247b5c03de8@reactivated.net> <20260728225727.148778-1-james.quinlan@broadcom.com> Content-Language: en-US From: Daniel Drake In-Reply-To: <20260728225727.148778-1-james.quinlan@broadcom.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 28/07/2026 23:57, Jim Quinlan wrote: >> +#define MMMU_CTRL_OPERATING_FLAGS (\ >> + MMMU_CTRL_CAP_EXCEEDED_ABORT_EN | \ >> + MMMU_CTRL_PT_INVALID_ABORT_EN | \ >> + MMMU_CTRL_PT_INVALID_EN | \ >> + MMMU_CTRL_WRITE_VIOLATION_ABORT_EN | \ >> + MMMU_CTRL_STATS_ENABLE | \ >> + MMMU_CTRL_ENABLE) > > Hello, > > Why not request the MMU interrupt and use the "INT_EN" version, e.g. > MMMU_CTRL_PT_INVALID_INT_EN? It seems better than "ABORT", as with an > interrupt you have a fighting chance of the handler printing out something > helpful and shutting down gracefully. That could indeed be useful, but the only info I have about this hardware is the RPi kernel's bcm2712-iommu driver which also does not handle this interrupt, so I don't have the required info to set up an interrupt handler. Could you let me know the interrupt routing details for all of the bcm2712 iommu blocks? e.g. which GIC/L2 IRQ lines they connect to. >> + /* Shootdown register deals with 4 pages at a time */ >> + for (page_group = iova >> (IOMMU_PAGE_SHIFT + 2); >> + page_group <= iova_end >> (IOMMU_PAGE_SHIFT + 2); page_group++) { >> + MMU_WR(MMMU_SHOOT_DOWN_OFFSET, >> + MMMU_SHOOT_DOWN_SHOOT + (page_group << 2)); >> + readl_poll_timeout_atomic( >> + mmu->reg_base + MMMU_SHOOT_DOWN_OFFSET, val, >> + !(val & MMMU_SHOOT_DOWN_SHOOTING), 0, 1000); > > I think it would be prudent to have this function return the > readl_poll_timeout_atomic() result and then do a dev_{warn,err}() call once > you are out of the containing spinlock. Also, why 1ms -- seems a long > time to have a spinlock. I'll do that. And yeah, that is way too long. I took some measurements and all 3 of the TLB-related cache flush codepaths take around 100ns on average. So I'm reducing the timeouts to 50usec. Thanks!