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Make dwmac4_release_tx_desc() clear all descriptor fields, not just TDES2 and TDES3. I'm suspecting that TDES0 and TDES1 wasn't cleared because the DMA engine uses them to store the tx hardware timestamp (if PTP is enabled). However, stmmac_tx_clean() calls stmmac_get_tx_hwtstamp(), which reads and saves the timestamp, before it calls release_tx_desc(), so this is not an issue. stmmac_xmit() and stmmac_tso_xmit() both always overwrite TDES0, however, stmmac_tso_xmit() sometimes sets TDES1, and since neither stmmac_xmit() nor stmmac_tso_xmit() explicitly clears TDES1, both functions might reuse a DMA descriptor with old TDES1 data. I haven't observed any misbehavior even though TDES1 sometimes point to an old skb, however, explicitly clearing both TDES0 and TDES1 in dwmac4_release_tx_desc() minimizes the chances of undefined behavior. Signed-off-by: Niklas Cassel <niklas.cassel@axis.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.