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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/29/24 06:40, ende.tan@starfivetech.com wrote: > From: Tan En De > > Minimize access to the RX descriptor by collecting all the flags in a > local variable and then updating the descriptor at once. > > Signed-off-by: Tan En De > --- > v3: > - Use local variable to batch set the descriptor flags. > - This reduces the number of accesses to the descriptor. > v2: https://patchwork.kernel.org/project/netdevbpf/patch/20240821060307.46350-1-ende.tan@starfivetech.com/ > - Avoid introducing a new function just to set the interrupt-on-completion > bit, as it is wasteful to do so. > - Delegate the responsibility of calling dma_wmb() from main driver code > to set_rx_owner() callbacks (i.e. let callbacks to manage the low-level > ordering/barrier rather than cluttering up the main driver code). > v1: https://patchwork.kernel.org/project/netdevbpf/patch/20240814092438.3129-1-ende.tan@starfivetech.com/ > --- > drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c | 6 ++++-- > drivers/net/ethernet/stmicro/stmmac/dwxgmac2_descs.c | 6 ++++-- > 2 files changed, 8 insertions(+), 4 deletions(-) > > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c > index 1c5802e0d7f4..dfcbe7036988 100644 > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c > @@ -186,10 +186,12 @@ static void dwmac4_set_tx_owner(struct dma_desc *p) > > static void dwmac4_set_rx_owner(struct dma_desc *p, int disable_rx_ic) > { > - p->des3 |= cpu_to_le32(RDES3_OWN | RDES3_BUFFER1_VALID_ADDR); > + u32 flags = cpu_to_le32(RDES3_OWN | RDES3_BUFFER1_VALID_ADDR); > > if (!disable_rx_ic) > - p->des3 |= cpu_to_le32(RDES3_INT_ON_COMPLETION_EN); > + flags |= cpu_to_le32(RDES3_INT_ON_COMPLETION_EN); > + > + p->des3 |= flags; You could just batch the endian conversion too: u32 flags = DES3_OWN | RDES3_BUFFER1_VALID_ADDR; if (!disable_rx_ic) flags |= RDES3_INT_ON_COMPLETION_EN; p->desc3 |= cpu_to_le32(flags); > } > > static int dwmac4_get_tx_ls(struct dma_desc *p) > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_descs.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_descs.c > index fc82862a612c..0c7ea939f787 100644 > --- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_descs.c > +++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_descs.c > @@ -56,10 +56,12 @@ static void dwxgmac2_set_tx_owner(struct dma_desc *p) > > static void dwxgmac2_set_rx_owner(struct dma_desc *p, int disable_rx_ic) > { > - p->des3 |= cpu_to_le32(XGMAC_RDES3_OWN); > + u32 flags = cpu_to_le32(XGMAC_RDES3_OWN); > > if (!disable_rx_ic) > - p->des3 |= cpu_to_le32(XGMAC_RDES3_IOC); > + flags |= cpu_to_le32(XGMAC_RDES3_IOC); > + > + p->des3 |= flags; And likewise here, and that would likely squash the sparse warning, since you would not be assigning an 'u32' field to a __le32 field anymore. -- Florian