On 23/12/2025 at 11:56, Arun Muthusamy wrote:
> From: Daniel Hellstrom <daniel@gaisler.com>
>
> Optimizes DMA transfers in the GRCAN driver by reorganizing
> data handling to use 32-bit accesses instead of individual
> byte accesses.
>
> Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>
> Signed-off-by: Arun Muthusamy <arun.muthusamy@gaisler.com>
> ---
> drivers/net/can/grcan.c | 22 +++++++++++-----------
> 1 file changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/can/grcan.c b/drivers/net/can/grcan.c
> index cac85fbe6acf..8a6c59473cf4 100644
> --- a/drivers/net/can/grcan.c
> +++ b/drivers/net/can/grcan.c
> @@ -1218,7 +1218,7 @@ static int grcan_receive(struct net_device *dev, int budget)
> struct sk_buff *skb;
> u32 wr, rd, startrd;
> u32 *slot;
> - u32 i, rtr, eff, j, shift;
> + u32 rtr, eff;
> int work_done = 0;
>
> rd = grcan_read_reg(®s->rxrd);
> @@ -1254,10 +1254,10 @@ static int grcan_receive(struct net_device *dev, int budget)
> if (rtr) {
> cf->can_id |= CAN_RTR_FLAG;
> } else {
> - for (i = 0; i < cf->len; i++) {
> - j = GRCAN_MSG_DATA_SLOT_INDEX(i);
> - shift = GRCAN_MSG_DATA_SHIFT(i);
> - cf->data[i] = (u8)(slot[j] >> shift);
> + if (cf->can_dlc > 0) {
> + memcpy(cf->data, &slot[2], sizeof(u32));
> + if (cf->can_dlc > 4)
> + memcpy(cf->data + 4, &slot[3], sizeof(u32));
> }
Nitpick: you may instead do:
if (cf->can_dlc > 0)
memcpy(cf->data, &slot[2], sizeof(u32));
if (cf->can_dlc > 4)
memcpy(cf->data + 4, &slot[3], sizeof(u32));
and let the compiler take care of the optimization for you ;)
>
> stats->rx_bytes += cf->len;
> @@ -1397,8 +1397,7 @@ static netdev_tx_t grcan_start_xmit(struct sk_buff *skb,
> u32 id, txwr, txrd, space, txctrl;
> int slotindex;
> u32 *slot;
> - u32 i, rtr, eff, dlc, tmp, err;
> - int j, shift;
> + u32 rtr, eff, dlc, tmp, err;
> unsigned long flags;
> u32 oneshotmode = priv->can.ctrlmode & CAN_CTRLMODE_ONE_SHOT;
>
> @@ -1451,10 +1450,11 @@ static netdev_tx_t grcan_start_xmit(struct sk_buff *skb,
> slot[1] = ((dlc << GRCAN_MSG_DLC_BIT) & GRCAN_MSG_DLC);
> slot[2] = 0;
> slot[3] = 0;
> - for (i = 0; i < dlc; i++) {
> - j = GRCAN_MSG_DATA_SLOT_INDEX(i);
> - shift = GRCAN_MSG_DATA_SHIFT(i);
> - slot[j] |= cf->data[i] << shift;
> + if (dlc > 0) {
> + memcpy(&slot[2], cf->data, sizeof(u32));
> + slot[2] = *(u32 *)(cf->data);
Why do you have both the memcpy() and the "slot[2] =" assignment?
> + if (dlc > 4)
> + memcpy(&slot[3], cf->data + 4, sizeof(u32));
> }
>
> /* Checking that channel has not been disabled. These cases
Don't forget also to remove the unused macros.
Yours sincerely,
Vincent Mailhol