GMAC_PLLCLK_DIV
writel(0, dwmac->apb_base + GMAC_PLLCLK_DIV);
writel(reg, dwmac->apb_base + GMAC_PLLCLK_DIV);
writel(0, dwmac->apb_base + GMAC_PLLCLK_DIV);
writel(reg, dwmac->apb_base + GMAC_PLLCLK_DIV);