ddr: altera: Add ECC DRAM scrubbing support for Arria10

The SDRAM must first be rewritten by zeroes if ECC is used to initialize
the ECC metadata. Make the CPU overwrite the DRAM with zeroes in such a
case. This scrubbing implementation turns the caches on temporarily, then
overwrites the whole RAM with zeroes, flushes the caches and turns them
off again. This provides satisfactory performance.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <chin.liang.see@intel.com>
Cc: Dinh Nguyen <dinguyen@kernel.org>

drivers/ddr/altera/sdram_arria10.c

@@ -215,6 +215,30 @@ static int ddr_setup(void)
 	return 0;
 }
 
+static int sdram_is_ecc_enabled(void)
+{
+	return !!(readl(&socfpga_ecc_hmc_base->eccctrl) &
+		  ALT_ECC_HMC_OCP_ECCCTL_ECC_EN_SET_MSK);
+}
+
+/* Initialize SDRAM ECC bits to avoid false DBE */
+static void sdram_init_ecc_bits(u32 size)
+{
+	icache_enable();
+
+	memset(0, 0, 0x8000);
+	gd->arch.tlb_addr = 0x4000;
+	gd->arch.tlb_size = PGTABLE_SIZE;
+
+	dcache_enable();
+
+	printf("DDRCAL: Scrubbing ECC RAM (%i MiB).\n", size >> 20);
+	memset((void *)0x8000, 0, size - 0x8000);
+	flush_dcache_all();
+	printf("DDRCAL: Scrubbing ECC RAM done.\n");
+	dcache_disable();
+}
+
 /* Function to startup the SDRAM*/
 static int sdram_startup(void)
 {
@@ -711,5 +735,8 @@ int ddr_calibration_sequence(void)
 	if (of_sdram_firewall_setup(gd->fdt_blob))
 		puts("FW: Error Configuring Firewall\n");
 
+	if (sdram_is_ecc_enabled())
+		sdram_init_ecc_bits(gd->ram_size);
+
 	return 0;
 }