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Wei Fang says: ==================== net: enetc: safely reinitialize TX BD ring when it has unsent frames Currently the driver does not reset the producer index register (PIR) and consumer index register (CIR) when initializing a TX BD ring. The driver only reads the PIR and CIR and initializes the software indexes. If the TX BD ring is reinitialized when it still contains unsent frames, its PIR and CIR will not be equal after the reinitialization. However, the BDs between CIR and PIR have been freed and become invalid and this can lead to a hardware malfunction, causing the TX BD ring will not work properly. Since the PIR and CIR are sofeware-configurable on ENETC v4. Therefore, the driver must reset them if they are not equal when reinitializing the TX BD ring. However, resetting the PIR and CIR alone is insufficient, it cannot completely solve the problem. When a link-down event occurs while the TX BD ring is transmitting frames, subsequent reinitialization of the TX BD ring may cause it to malfunction. Because enetc4_pl_mac_link_down() only clears PMa_COMMAND_CONFIG[TX_EN] to disable MAC transmit data path. It doesn't set PORT[TXDIS] to 1 to flush the TX BD ring. Therefore, it is not safe to reinitialize the TX BD ring at this point. To safely reinitialize the TX BD ring after a link-down event, we checked with the NETC IP team, a proper Ethernet MAC graceful stop is necessary. Therefore, add the Ethernet MAC graceful stop to the link-down event handler enetc4_pl_mac_link_down(). Note that this patch set is not applicable to ENETC v1 (LS1028A). ==================== Link: https://patch.msgid.link/20260324062121.2745033-1-wei.fang@nxp.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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