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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Oleksij Rempel , kernel@pengutronix.de, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH net-next v2 1/1] net: macb: fix negative max_mtu size for sama5d3 Date: Fri, 17 Jun 2022 09:16:07 +0200 Message-Id: <20220617071607.3782772-1-o.rempel@pengutronix.de> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: ore@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org JML register on probe will return zero . This register is configured later on macb_init_hw() which is called on open. Since we have zero, after header and FCS length subtraction we will get negative max_mtu size. This issue was affecting DSA drivers with MTU support (for example KSZ9477). Signed-off-by: Oleksij Rempel --- changes v2: - properly describe fail reason - simplify max_mtu logic drivers/net/ethernet/cadence/macb_main.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c index d89098f4ede8..d0ea8dbfa213 100644 --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c @@ -4913,8 +4913,8 @@ static int macb_probe(struct platform_device *pdev) /* MTU range: 68 - 1500 or 10240 */ dev->min_mtu = GEM_MTU_MIN_SIZE; - if (bp->caps & MACB_CAPS_JUMBO) - dev->max_mtu = gem_readl(bp, JML) - ETH_HLEN - ETH_FCS_LEN; + if ((bp->caps & MACB_CAPS_JUMBO) && bp->jumbo_max_len) + dev->max_mtu = bp->jumbo_max_len - ETH_HLEN - ETH_FCS_LEN; else dev->max_mtu = ETH_DATA_LEN; -- 2.30.2