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Wed, 12 Aug 2026 09:38:37 -0700 (PDT) From: Alex Elder To: maxime.chevallier@bootlin.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: sashiko-bot@kernel.org, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com, linux-stm32@st-md-mailman.stormreply.com, netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH net-next v2 2/2] net: stmmac: convert DMA address to lower 32 before assignment Date: Wed, 12 Aug 2026 11:38:31 -0500 Message-ID: <20260812163832.271742-3-elder@riscstar.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260812163832.271742-1-elder@riscstar.com> References: <20260812163832.271742-1-elder@riscstar.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In jumbo_frm() (implemented in both "chain_mode.c" and "ring_mode.c"), there are places where a DMA descriptor is converted to little-endian byte order in assignment. The DMA descriptor could be a 64-bit value, which makes the 32-bit byte swapping operation seem a little sketchy. Explicitly extract the low-order 32 bits of the dma_addr_t value being converted into a u32 so it's crystal clear that we're doing the right thing. Suggested-by: Maxime Chevallier Signed-off-by: Alex Elder --- drivers/net/ethernet/stmicro/stmmac/chain_mode.c | 6 +++--- drivers/net/ethernet/stmicro/stmmac/ring_mode.c | 12 ++++++------ 2 files changed, 9 insertions(+), 9 deletions(-) diff --git a/drivers/net/ethernet/stmicro/stmmac/chain_mode.c b/drivers/net/ethernet/stmicro/stmmac/chain_mode.c index ec25193d287bb..66025e2509e91 100644 --- a/drivers/net/ethernet/stmicro/stmmac/chain_mode.c +++ b/drivers/net/ethernet/stmicro/stmmac/chain_mode.c @@ -37,7 +37,7 @@ static int jumbo_frm(struct stmmac_tx_queue *tx_q, struct sk_buff *skb, des2 = dma_map_single(priv->device, skb->data, buf_len, DMA_TO_DEVICE); - desc->des2 = cpu_to_le32(des2); + desc->des2 = cpu_to_le32(lower_32_bits(des2)); if (dma_mapping_error(priv->device, des2)) return -1; tx_q->tx_skbuff_dma[entry].buf = des2; @@ -55,7 +55,7 @@ static int jumbo_frm(struct stmmac_tx_queue *tx_q, struct sk_buff *skb, des2 = dma_map_single(priv->device, (skb->data + bmax * i), bmax, DMA_TO_DEVICE); - desc->des2 = cpu_to_le32(des2); + desc->des2 = cpu_to_le32(lower_32_bits(des2)); if (dma_mapping_error(priv->device, des2)) return -1; tx_q->tx_skbuff_dma[entry].buf = des2; @@ -68,7 +68,7 @@ static int jumbo_frm(struct stmmac_tx_queue *tx_q, struct sk_buff *skb, des2 = dma_map_single(priv->device, (skb->data + bmax * i), len, DMA_TO_DEVICE); - desc->des2 = cpu_to_le32(des2); + desc->des2 = cpu_to_le32(lower_32_bits(des2)); if (dma_mapping_error(priv->device, des2)) return -1; tx_q->tx_skbuff_dma[entry].buf = des2; diff --git a/drivers/net/ethernet/stmicro/stmmac/ring_mode.c b/drivers/net/ethernet/stmicro/stmmac/ring_mode.c index 664d8cfb58cdc..f7949419eb9fd 100644 --- a/drivers/net/ethernet/stmicro/stmmac/ring_mode.c +++ b/drivers/net/ethernet/stmicro/stmmac/ring_mode.c @@ -40,7 +40,7 @@ static int jumbo_frm(struct stmmac_tx_queue *tx_q, struct sk_buff *skb, des2 = dma_map_single(priv->device, skb->data, bmax, DMA_TO_DEVICE); - desc->des2 = cpu_to_le32(des2); + desc->des2 = cpu_to_le32(lower_32_bits(des2)); if (dma_mapping_error(priv->device, des2)) return -1; @@ -48,7 +48,7 @@ static int jumbo_frm(struct stmmac_tx_queue *tx_q, struct sk_buff *skb, tx_q->tx_skbuff_dma[entry].len = bmax; tx_q->tx_skbuff_dma[entry].is_jumbo = true; - desc->des3 = cpu_to_le32(des2 + BUF_SIZE_4KiB); + desc->des3 = cpu_to_le32(lower_32_bits(des2) + BUF_SIZE_4KiB); stmmac_prepare_tx_desc(priv, desc, 1, bmax, csum, STMMAC_RING_MODE, 0, false, skb->len); tx_q->tx_skbuff[entry] = NULL; @@ -61,27 +61,27 @@ static int jumbo_frm(struct stmmac_tx_queue *tx_q, struct sk_buff *skb, des2 = dma_map_single(priv->device, skb->data + bmax, len, DMA_TO_DEVICE); - desc->des2 = cpu_to_le32(des2); + desc->des2 = cpu_to_le32(lower_32_bits(des2)); if (dma_mapping_error(priv->device, des2)) return -1; tx_q->tx_skbuff_dma[entry].buf = des2; tx_q->tx_skbuff_dma[entry].len = len; tx_q->tx_skbuff_dma[entry].is_jumbo = true; - desc->des3 = cpu_to_le32(des2 + BUF_SIZE_4KiB); + desc->des3 = cpu_to_le32(lower_32_bits(des2) + BUF_SIZE_4KiB); stmmac_prepare_tx_desc(priv, desc, 0, len, csum, STMMAC_RING_MODE, 1, !skb_is_nonlinear(skb), skb->len); } else { des2 = dma_map_single(priv->device, skb->data, nopaged_len, DMA_TO_DEVICE); - desc->des2 = cpu_to_le32(des2); + desc->des2 = cpu_to_le32(lower_32_bits(des2)); if (dma_mapping_error(priv->device, des2)) return -1; tx_q->tx_skbuff_dma[entry].buf = des2; tx_q->tx_skbuff_dma[entry].len = nopaged_len; tx_q->tx_skbuff_dma[entry].is_jumbo = true; - desc->des3 = cpu_to_le32(des2 + BUF_SIZE_4KiB); + desc->des3 = cpu_to_le32(lower_32_bits(des2) + BUF_SIZE_4KiB); stmmac_prepare_tx_desc(priv, desc, 1, nopaged_len, csum, STMMAC_RING_MODE, 0, !skb_is_nonlinear(skb), skb->len); -- 2.53.0