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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , Robert Hancock , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, stable@vger.kernel.org Subject: Re: [PATCH net 1/2] net: macb: reprogram TBQP after shuffling the TX ring on link-up Message-ID: References: <20260706-upstreaming-macb-irq-storm-v1-0-ab3115b5a13a@weidmueller.com> <20260706-upstreaming-macb-irq-storm-v1-1-ab3115b5a13a@weidmueller.com> <8d53c3d9-7918-456c-8c27-e9d73c896452@weidmueller.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="kyG29oqcChhEWuEU" Content-Disposition: inline In-Reply-To: <8d53c3d9-7918-456c-8c27-e9d73c896452@weidmueller.com> --kyG29oqcChhEWuEU Content-Type: text/plain; charset=us-ascii Content-Disposition: inline > I agree that the TRM says the transmit pointer is reset while TE is low. My > question is whether this describes an internal pointer being reloaded from TBQP, > or whether TBQP itself is restored to the original ring base. The Zynq UltraScale TRM [1] describes the receive-buffer queue pointer as follows: An internal counter represents the receive-buffer queue pointer and it is not visible through the CPU interface. I could not find a similar description for the transmit-buffer queue pointer, but I believe it behaves the same way. From a software perspective, it should be safe to assume that the TBQP is reset to point to the start of the transmit descriptor list upon reset. This assumption is supported by the description of the transmit_q_ptr (GEM) Register [2]: Reading this register returns the location of the descriptor currently being accessed. Since the DMA handles two frames at once, this may not necessarily be pointing to the current frame being transmitted. [1] https://docs.amd.com/v/u/en-US/ug1085-zynq-ultrascale-trm [2] https://docs.amd.com/r/en-US/ug1087-zynq-ultrascale-registers/transmit_q_ptr-GEM-Register Thanks, Kevin --kyG29oqcChhEWuEU Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEHc6qFoLCZqgJD98Zk1jtMN6usXEFAmpNvlsACgkQk1jtMN6u sXEU6Qf9ENUqNjx8NFL9ReOVIph7o6p3txHaKrhJNj5yOldBQKaAhd3ulWrxdDo+ mBtBwyWjckjL6a66Nknb+FHUYCOSThofTjjzujesS5acHoyVDfTOn4ygarN4h3gx Vo9tcn9AaxvJi91DZPS0pGMyZgw0LVgiWwBwW29/z/hjn2bnvVRh8+VuCCEUPwjE 32Zn7Oqe4fk6yghgBVebUAn1LcySVtLRm0Xxi2nJw6k4GFdeb8RJ8hTTz9jGrBz4 Tq4oYVreIMzMfcC3G4vqKpinByTiswzqoXhFDlPXup8X6zu6DecFqWdz3isOa+4D A7RfNYlyO90plRZbnLNauVS1oQZucw== =QDLt -----END PGP SIGNATURE----- --kyG29oqcChhEWuEU--