qed: allow the callee of qed_mcp_nvm_read() to sleep

qed_mcp_nvm_read has a loop where it calls qed_mcp_nvm_rd_cmd with the
argument b_can_sleep=false. And it sleeps once every 0x1000 bytes
read.

Simplify this by letting qed_mcp_nvm_rd_cmd itself sleep
(b_can_sleep=true). It will have slept at least once when successful
(in the "Wait for the MFW response" loop). So the extra sleep once every
0x1000 bytes becomes superfluous. Delete it.

On my test system with voluntary preemption, this lowers the latency
caused by 'ethtool -d' from 53 ms to 10 ms.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Link: https://patch.msgid.link/20240930201307.330692-4-mschmidt@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/qlogic/qed/qed_mcp.c

@@ -3079,20 +3079,13 @@ int qed_mcp_nvm_read(struct qed_dev *cdev, u32 addr, u8 *p_buf, u32 len)
 					 DRV_MB_PARAM_NVM_LEN_OFFSET),
 					&resp, &resp_param,
 					&read_len,
-					(u32 *)(p_buf + offset), false);
+					(u32 *)(p_buf + offset), true);
 
 		if (rc || (resp != FW_MSG_CODE_NVM_OK)) {
 			DP_NOTICE(cdev, "MCP command rc = %d\n", rc);
 			break;
 		}
 
-		/* This can be a lengthy process, and it's possible scheduler
-		 * isn't preemptible. Sleep a bit to prevent CPU hogging.
-		 */
-		if (bytes_left % 0x1000 <
-		    (bytes_left - read_len) % 0x1000)
-			usleep_range(1000, 2000);
-
 		offset += read_len;
 		bytes_left -= read_len;
 	}