ASPEED_PECI_CLK_DIV1
(4 * ASPEED_PECI_CLK_DIV1(msg_timing) * ASPEED_PECI_CLK_DIV2(clk_div_exp))
diff = abs(rate - ASPEED_PECI_CLK_DIV1(i) * ASPEED_PECI_CLK_DIV2(j));