On Fri, Feb 24, 2017 at 9:23 AM, Benjamin Herrenschmidt
[off-list ref] wrote:

 static int ast_get_dram_info(struct drm_device *dev)
 {
+       struct device_node *np = dev->pdev->dev.of_node;
        struct ast_private *ast = dev->dev_private;
-       uint32_t data, data2;
-       uint32_t denum, num, div, ref_pll;
+       uint32_t mcr_cfg, mcr_scu_mpll, mcr_scu_strap;
+       uint32_t denum, num, div, ref_pll, dsel;

-       if (ast->DisableP2A)
-       {
+       switch (ast->config_mode) {
+       case ast_use_dt:
+               /*
+                * If some properties are missing, use reasonable
+                * defaults for AST2400
+                */
+               if (of_property_read_u32(np, "ast,mcr-configuration", &mcr_cfg))
+                       mcr_cfg = 0x00000577;
+               if (of_property_read_u32(np, "ast,ast,mcr-scu-mpll",
+                                        &mcr_scu_mpll))
+                       mcr_scu_mpll = 0x000050C0;
+               if (of_property_read_u32(np, "ast,ast,mcr-scu-strap",

Are these properties supposed to repeat the prefix "ast,ast"?

We've chosen aspeed as the vendor prefix for Aspeed stuff.

+                                        &mcr_scu_strap))
+                       mcr_scu_strap = 0;
+               break;
+       case ast_use_p2a:
+               ast_write32(ast, 0xf004, 0x1e6e0000);
+               ast_write32(ast, 0xf000, 0x1);
+               mcr_cfg = ast_read32(ast, 0x10004);
+               mcr_scu_mpll = ast_read32(ast, 0x10120);
+               mcr_scu_strap = ast_read32(ast, 0x10170);
+               break;
+       case ast_use_defaults:
+       default:
                ast->dram_bus_width = 16;
                ast->dram_type = AST_DRAM_1Gx16;
                ast->mclk = 396;
+               return 0;
        }
-       else
-       {
-               ast_write32(ast, 0xf004, 0x1e6e0000);
-               ast_write32(ast, 0xf000, 0x1);
-               data = ast_read32(ast, 0x10004);

-               if (data & 0x40)
-                       ast->dram_bus_width = 16;
-               else
-                       ast->dram_bus_width = 32;
-
-               if (ast->chip == AST2300 || ast->chip == AST2400) {
-                       switch (data & 0x03) {
-                       case 0:
-                               ast->dram_type = AST_DRAM_512Mx16;
-                               break;
-                       default:
-                       case 1:
-                               ast->dram_type = AST_DRAM_1Gx16;
-                               break;
-                       case 2:
-                               ast->dram_type = AST_DRAM_2Gx16;
-                               break;
-                       case 3:
-                               ast->dram_type = AST_DRAM_4Gx16;
-                               break;
-                       }
-               } else {
-                       switch (data & 0x0c) {
-                       case 0:
-                       case 4:
-                               ast->dram_type = AST_DRAM_512Mx16;
-                               break;
-                       case 8:
-                               if (data & 0x40)
-                                       ast->dram_type = AST_DRAM_1Gx16;
-                               else
-                                       ast->dram_type = AST_DRAM_512Mx32;
-                               break;
-                       case 0xc:
-                               ast->dram_type = AST_DRAM_1Gx32;
-                               break;
-                       }
-               }
+       if (mcr_cfg & 0x40)
+               ast->dram_bus_width = 16;
+       else
+               ast->dram_bus_width = 32;

-               data = ast_read32(ast, 0x10120);
-               data2 = ast_read32(ast, 0x10170);
-               if (data2 & 0x2000)
-                       ref_pll = 14318;
-               else
-                       ref_pll = 12000;
-
-               denum = data & 0x1f;
-               num = (data & 0x3fe0) >> 5;
-               data = (data & 0xc000) >> 14;
-               switch (data) {
-               case 3:
-                       div = 0x4;
+       if (ast->chip == AST2300 || ast->chip == AST2400) {
+               switch (mcr_cfg & 0x03) {
+               case 0:
+                       ast->dram_type = AST_DRAM_512Mx16;
                        break;
-               case 2:
+               default:
                case 1:
-                       div = 0x2;
+                       ast->dram_type = AST_DRAM_1Gx16;
                        break;
-               default:
-                       div = 0x1;
+               case 2:
+                       ast->dram_type = AST_DRAM_2Gx16;
+                       break;
+               case 3:
+                       ast->dram_type = AST_DRAM_4Gx16;
                        break;
                }
-               ast->mclk = ref_pll * (num + 2) / (denum + 2) * (div * 1000);
+       } else {
+               switch (mcr_cfg & 0x0c) {
+               case 0:
+               case 4:
+                       ast->dram_type = AST_DRAM_512Mx16;
+                       break;
+               case 8:
+                       if (mcr_cfg & 0x40)
+                               ast->dram_type = AST_DRAM_1Gx16;
+                       else
+                               ast->dram_type = AST_DRAM_512Mx32;
+                       break;
+               case 0xc:
+                       ast->dram_type = AST_DRAM_1Gx32;
+                       break;
+               }
+       }
+
+       if (mcr_scu_strap & 0x2000)

This bit confused me. Bit 13 of the strap (SCU70) is the SPI mode.

+               ref_pll = 14318;
+       else
+               ref_pll = 12000;
+
+       denum = mcr_scu_mpll & 0x1f;
+       num = (mcr_scu_mpll & 0x3fe0) >> 5;
+       dsel = (mcr_scu_mpll & 0xc000) >> 14;

These calculations don't make sense for the ast2400 or ast2500.

+       switch (dsel) {
+       case 3:
+               div = 0x4;
+               break;
+       case 2:
+       case 1:
+               div = 0x2;
+               break;
+       default:
+               div = 0x1;
+               break;
        }
+       ast->mclk = ref_pll * (num + 2) / (denum + 2) * (div * 1000);
        return 0;
 }