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[34.142.255.199]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8434ad03fdcsm10547347b3a.24.2026.06.15.10.43.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Jun 2026 10:43:43 -0700 (PDT) Date: Mon, 15 Jun 2026 17:43:37 +0000 From: Pranjal Shrivastava To: Mostafa Saleh Cc: iommu@lists.linux.dev, Will Deacon , Joerg Roedel , Robin Murphy , Jason Gunthorpe , Nicolin Chen , Daniel Mentz , Ashish Mhetre , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v8 04/12] iommu/tegra241-cmdqv: Restore PROD and CONS after resume Message-ID: References: <20260601215909.3958732-1-praan@google.com> <20260601215909.3958732-5-praan@google.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Jun 15, 2026 at 05:01:34PM +0000, Mostafa Saleh wrote: > On Mon, Jun 01, 2026 at 09:59:01PM +0000, Pranjal Shrivastava wrote: > > From: Ashish Mhetre > > > > PROD and CONS indices for vcmdqs are getting set to 0 after resume. > > Because of this the vcmdq is not consuming commands after resume. > > Fix this by restoring PROD and CONS indices after resume from > > saved pointers. > > What commands are exisiting at resume? Won't > tegra241_cmdqv_drain_vintf0_lvcmdqs() drain the queues and make the > PROD and CONS equal each other anyway? The SW prod / cons are indeed equal because of the queue drain before suspend. However, the HW registers in vCMDQ reset to 0 on a power-cycle Now, if we resume with the software prod/cons at 100/100, since the HW prod/cons is at 0/0, when the driver then issues a new command and only updates the PROD register to 101, the HW will see (CONS=0, PROD=101). The arm-smmu-v3 driver restores these indices correctly in device_reset but the Tegra VMDQV driver doesn't. Thus, this patch was added to restore both indices ensuring the HW doesn't de-sync. This was added after Ashish tested an older version of the series [1] with Tegra, Thanks, Praan [1] https://lore.kernel.org/all/6afc3e46-489e-4741-96d5-8a2f72a8b431@nvidia.com/