can: mcp251xfd: mcp251xfd_tx_obj_from_skb(): don't copy data for RTR CAN frames in...

In Classical CAN there are RTR frames. RTR frames have the RTR bit set, may
have a dlc != 0, but contain no data.

This patch optimizes the TX-path to not copy any data for RTR frames.

Link: https://lore.kernel.org/r/20210114153448.1506901-5-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
index 92816be..e6d98e1 100644 (file)
--- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
+++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
@@ -2304,7 +2304,7 @@ mcp251xfd_tx_obj_from_skb(const struct mcp251xfd_priv *priv,
        union mcp251xfd_tx_obj_load_buf *load_buf;
        u8 dlc;
        u32 id, flags;
-       int pad_len, len;
+       int len_sanitized = 0, len;
 
        if (cfd->can_id & CAN_EFF_FLAG) {
                u32 sid, eid;
@@ -2331,6 +2331,8 @@ mcp251xfd_tx_obj_from_skb(const struct mcp251xfd_priv *priv,
 
        if (cfd->can_id & CAN_RTR_FLAG)
                flags |= MCP251XFD_OBJ_FLAGS_RTR;
+       else
+               len_sanitized = canfd_sanitize_len(cfd->len);
 
        /* CANFD */
        if (can_is_canfd_skb(skb)) {
@@ -2356,14 +2358,18 @@ mcp251xfd_tx_obj_from_skb(const struct mcp251xfd_priv *priv,
        memcpy(hw_tx_obj->data, cfd->data, cfd->len);
 
        /* Clear unused data at end of CAN frame */
-       pad_len = can_fd_dlc2len(dlc) - cfd->len;
-       if (MCP251XFD_SANITIZE_CAN && pad_len)
-               memset(hw_tx_obj->data + cfd->len, 0x0, pad_len);
+       if (MCP251XFD_SANITIZE_CAN && len_sanitized) {
+               int pad_len;
+
+               pad_len = len_sanitized - cfd->len;
+               if (pad_len)
+                       memset(hw_tx_obj->data + cfd->len, 0x0, pad_len);
+       }
 
        /* Number of bytes to be written into the RAM of the controller */
        len = sizeof(hw_tx_obj->id) + sizeof(hw_tx_obj->flags);
        if (MCP251XFD_SANITIZE_CAN)
-               len += round_up(can_fd_dlc2len(dlc), sizeof(u32));
+               len += round_up(len_sanitized, sizeof(u32));
        else
                len += round_up(cfd->len, sizeof(u32));