sunxi: dram: Drop DDR2 support and assume only single rank DDR3 memory

All the known Allwinner A10/A13/A20 devices are using just single rank
DDR3 memory. So don't pretend that we support DDR2 or more than one
rank, because nobody could ever test these configurations for real and
they are likely broken. Support for these features can be added back
in the case if such hardware actually exists.

As part of this code cleanup, also replace division by 1024 with
division by 1000 for the refresh timing calculations. This allows
to use the original non-skewed tRFC timing table from the DRR3 spec
and make code less confusing.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

diff --git a/arch/arm/cpu/armv7/sunxi/dram.c b/arch/arm/cpu/armv7/sunxi/dram.c
index be6750d..0bbb10d 100644 (file)
--- a/arch/arm/cpu/armv7/sunxi/dram.c
+++ b/arch/arm/cpu/armv7/sunxi/dram.c
@@ -434,20 +434,18 @@ static void dramc_clock_output_en(u32 on)
 #endif
 }
 
-static const u16 tRFC_table[2][6] = {
-       /*       256Mb    512Mb    1Gb      2Gb      4Gb      8Gb      */
-       /* DDR2  75ns     105ns    127.5ns  195ns    327.5ns  invalid  */
-       {        77,      108,     131,     200,     336,     336 },
-       /* DDR3  invalid  90ns     110ns    160ns    300ns    350ns    */
-       {        93,      93,      113,     164,     308,     359 }
+/* tRFC in nanoseconds for different densities (from the DDR3 spec) */
+static const u16 tRFC_DDR3_table[6] = {
+       /* 256Mb    512Mb    1Gb      2Gb      4Gb      8Gb */
+          90,      90,      110,     160,     300,     350
 };
 
-static void dramc_set_autorefresh_cycle(u32 clk, u32 type, u32 density)
+static void dramc_set_autorefresh_cycle(u32 clk, u32 density)
 {
        struct sunxi_dram_reg *dram = (struct sunxi_dram_reg *)SUNXI_DRAMC_BASE;
        u32 tRFC, tREFI;
 
-       tRFC = (tRFC_table[type][density] * clk + 1023) >> 10;
+       tRFC = (tRFC_DDR3_table[density] * clk + 999) / 1000;
        tREFI = (7987 * clk) >> 10;     /* <= 7.8us */
 
        writel(DRAM_DRR_TREFI(tREFI) | DRAM_DRR_TRFC(tRFC), &dram->drr);
@@ -570,6 +568,13 @@ unsigned long dramc_init(struct dram_para *para)
        if (!para)
                return 0;
 
+       /*
+        * only single rank DDR3 is supported by this code even though the
+        * hardware can theoretically support DDR2 and up to two ranks
+        */
+       if (para->type != DRAM_MEMORY_TYPE_DDR3 || para->rank_num != 1)
+               return 0;
+
        /* setup DRAM relative clock */
        mctl_setup_dram_clock(para->clock, para->mbus_clock);
 
@@ -590,9 +595,7 @@ unsigned long dramc_init(struct dram_para *para)
        mctl_enable_dll0(para->tpr3);
 
        /* configure external DRAM */
-       reg_val = 0x0;
-       if (para->type == DRAM_MEMORY_TYPE_DDR3)
-               reg_val |= DRAM_DCR_TYPE_DDR3;
+       reg_val = DRAM_DCR_TYPE_DDR3;
        reg_val |= DRAM_DCR_IO_WIDTH(para->io_width >> 3);
 
        if (para->density == 256)
@@ -632,25 +635,19 @@ unsigned long dramc_init(struct dram_para *para)
        mctl_enable_dllx(para->tpr3);
 
        /* set refresh period */
-       dramc_set_autorefresh_cycle(para->clock, para->type - 2, density);
+       dramc_set_autorefresh_cycle(para->clock, density);
 
        /* set timing parameters */
        writel(para->tpr0, &dram->tpr0);
        writel(para->tpr1, &dram->tpr1);
        writel(para->tpr2, &dram->tpr2);
 
-       if (para->type == DRAM_MEMORY_TYPE_DDR3) {
-               reg_val = DRAM_MR_BURST_LENGTH(0x0);
+       reg_val = DRAM_MR_BURST_LENGTH(0x0);
 #if (defined(CONFIG_SUN5I) || defined(CONFIG_SUN7I))
-               reg_val |= DRAM_MR_POWER_DOWN;
+       reg_val |= DRAM_MR_POWER_DOWN;
 #endif
-               reg_val |= DRAM_MR_CAS_LAT(para->cas - 4);
-               reg_val |= DRAM_MR_WRITE_RECOVERY(0x5);
-       } else if (para->type == DRAM_MEMORY_TYPE_DDR2) {
-               reg_val = DRAM_MR_BURST_LENGTH(0x2);
-               reg_val |= DRAM_MR_CAS_LAT(para->cas);
-               reg_val |= DRAM_MR_WRITE_RECOVERY(0x5);
-       }
+       reg_val |= DRAM_MR_CAS_LAT(para->cas - 4);
+       reg_val |= DRAM_MR_WRITE_RECOVERY(0x5);
        writel(reg_val, &dram->mr);
 
        writel(para->emr1, &dram->emr);