--- zzzz-none-000/linux-4.19.183/arch/arm64/mm/init.c	2021-03-24 10:07:39.000000000 +0000
+++ bcm63-7530ax-756/linux-4.19.183/arch/arm64/mm/init.c	2023-06-28 08:54:18.000000000 +0000
@@ -224,7 +224,14 @@
 static phys_addr_t __init max_zone_dma_phys(void)
 {
 	phys_addr_t offset = memblock_start_of_DRAM() & GENMASK_ULL(63, 32);
+#if defined(CONFIG_BCM_KF_ARM64_BCM963XX) && defined(CONFIG_BCM94908) && defined(CONFIG_BCM_HND_EAP)
+	/* Using ZONE_DMA to work around a 4908 Ethernet packet transmission
+	 * performance issue when packet buffer is located at address
+	 * larger than 1GB. */
+	return min(offset + (1ULL << 30), memblock_end_of_DRAM());
+#else
 	return min(offset + (1ULL << 32), memblock_end_of_DRAM());
+#endif
 }
 
 #ifdef CONFIG_NUMA