[Qemu-devel] [PATCH 1/3] aspeed/scu: introduce clock frequencies

["Cédric Le Goater" <clg@kaod.org>]

All Aspeed SoC clocks are driven by an input source clock which can
have different frequencies : 24MHz or 25MHz, and also, on the Aspeed
AST2400 SoC, 48MHz. The H-PLL (CPU) clock is defined from a
calculation using parameters in the H-PLL Parameter register or from a
predefined set of frequencies if the setting is strapped by hardware
(Aspeed AST2400 SoC). The other clocks of the SoC are then defined
from the H-PLL using dividers.

We introduce first the APB clock because it drives the timer.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
---
 include/hw/misc/aspeed_scu.h |  70 ++++++++++++++++++++++++++--
 hw/misc/aspeed_scu.c         | 106 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 172 insertions(+), 4 deletions(-)

diff --git a/include/hw/misc/aspeed_scu.h b/include/hw/misc/aspeed_scu.h
index d70cc0aeca61..f662c38188f4 100644
--- a/include/hw/misc/aspeed_scu.h
+++ b/include/hw/misc/aspeed_scu.h
@@ -30,6 +30,10 @@ typedef struct AspeedSCUState {
     uint32_t hw_strap1;
     uint32_t hw_strap2;
     uint32_t hw_prot_key;
+
+    uint32_t clkin;
+    uint32_t hpll;
+    uint32_t apb_freq;
 } AspeedSCUState;
 
 #define AST2400_A0_SILICON_REV   0x02000303U
@@ -58,7 +62,64 @@ extern bool is_supported_silicon_rev(uint32_t silicon_rev);
  *       1. 2012/12/29 Ryan Chen Create
  */
 
-/* Hardware Strapping Register definition (for Aspeed AST2400 SOC)
+/* SCU08   Clock Selection Register
+ *
+ *  31     Enable Video Engine clock dynamic slow down
+ *  30:28  Video Engine clock slow down setting
+ *  27     2D Engine GCLK clock source selection
+ *  26     2D Engine GCLK clock throttling enable
+ *  25:23  APB PCLK divider selection
+ *  22:20  LPC Host LHCLK divider selection
+ *  19     LPC Host LHCLK clock generation/output enable control
+ *  18:16  MAC AHB bus clock divider selection
+ *  15     SD/SDIO clock running enable
+ *  14:12  SD/SDIO divider selection
+ *  11     Reserved
+ *  10:8   Video port output clock delay control bit
+ *  7      ARM CPU/AHB clock slow down enable
+ *  6:4    ARM CPU/AHB clock slow down setting
+ *  3:2    ECLK clock source selection
+ *  1      CPU/AHB clock slow down idle timer
+ *  0      CPU/AHB clock dynamic slow down enable (defined in bit[6:4])
+ */
+#define SCU_CLK_GET_PCLK_DIV(x)                    (((x) >> 23) & 0x7)
+
+/* SCU24   H-PLL Parameter Register (for Aspeed AST2400 SOC)
+ *
+ *  18     H-PLL parameter selection
+ *           0: Select H-PLL by strapping resistors
+ *           1: Select H-PLL by the programmed registers (SCU24[17:0])
+ *  17     Enable H-PLL bypass mode
+ *  16     Turn off H-PLL
+ *  10:5   H-PLL Numerator
+ *  4      H-PLL Output Divider
+ *  3:0    H-PLL Denumerator
+ *
+ *  (Output frequency) = 24MHz * (2-OD) * [(Numerator+2) / (Denumerator+1)]
+ */
+
+#define SCU_AST2400_H_PLL_PROGRAMMED               (0x1 << 18)
+#define SCU_AST2400_H_PLL_BYPASS_EN                (0x1 << 17)
+#define SCU_AST2400_H_PLL_OFF                      (0x1 << 16)
+
+/* SCU24   H-PLL Parameter Register (for Aspeed AST2500 SOC)
+ *
+ *  21     Enable H-PLL reset
+ *  20     Enable H-PLL bypass mode
+ *  19     Turn off H-PLL
+ *  18:13  H-PLL Post Divider
+ *  12:5   H-PLL Numerator (M)
+ *  4:0    H-PLL Denumerator (N)
+ *
+ *  (Output frequency) = CLKIN(24MHz) * [(M+1) / (N+1)] / (P+1)
+ *
+ * The default frequency is 792Mhz when CLKIN = 24MHz
+ */
+
+#define SCU_H_PLL_BYPASS_EN                        (0x1 << 20)
+#define SCU_H_PLL_OFF                              (0x1 << 19)
+
+/* SCU70  Hardware Strapping Register definition (for Aspeed AST2400 SOC)
  *
  * 31:29  Software defined strapping registers
  * 28:27  DRAM size setting (for VGA driver use)
@@ -107,12 +168,13 @@ extern bool is_supported_silicon_rev(uint32_t silicon_rev);
 #define SCU_AST2400_HW_STRAP_GET_CLK_SOURCE(x)     (((((x) >> 23) & 0x1) << 1) \
                                                     | (((x) >> 18) & 0x1))
 #define SCU_AST2400_HW_STRAP_CLK_SOURCE_MASK       ((0x1 << 23) | (0x1 << 18))
-#define     AST2400_CLK_25M_IN                         (0x1 << 23)
+#define SCU_HW_STRAP_CLK_25M_IN                    (0x1 << 23)
 #define     AST2400_CLK_24M_IN                         0
 #define     AST2400_CLK_48M_IN                         1
 #define     AST2400_CLK_25M_IN_24M_USB_CKI             2
 #define     AST2400_CLK_25M_IN_48M_USB_CKI             3
 
+#define SCU_HW_STRAP_CLK_48M_IN                    (0x1 << 18)
 #define SCU_HW_STRAP_2ND_BOOT_WDT                  (0x1 << 17)
 #define SCU_HW_STRAP_SUPER_IO_CONFIG               (0x1 << 16)
 #define SCU_HW_STRAP_VGA_CLASS_CODE                (0x1 << 15)
@@ -160,8 +222,8 @@ extern bool is_supported_silicon_rev(uint32_t silicon_rev);
 #define     AST2400_DIS_BOOT                           3
 
 /*
- * Hardware strapping register definition (for Aspeed AST2500 SoC and
- * higher)
+ * SCU70  Hardware strapping register definition (for Aspeed AST2500
+ *        SoC and higher)
  *
  * 31     Enable SPI Flash Strap Auto Fetch Mode
  * 30     Enable GPIO Strap Mode
diff --git a/hw/misc/aspeed_scu.c b/hw/misc/aspeed_scu.c
index 59315010db9a..a17d50edd78d 100644
--- a/hw/misc/aspeed_scu.c
+++ b/hw/misc/aspeed_scu.c
@@ -168,6 +168,27 @@ static uint32_t aspeed_scu_get_random(void)
     return num;
 }
 
+static void aspeed_scu_set_apb_freq(AspeedSCUState *s)
+{
+    uint32_t apb_divider;
+
+    switch (s->silicon_rev) {
+    case AST2400_A0_SILICON_REV:
+    case AST2400_A1_SILICON_REV:
+        apb_divider = 2;
+        break;
+    case AST2500_A0_SILICON_REV:
+    case AST2500_A1_SILICON_REV:
+        apb_divider = 4;
+        break;
+    default:
+        g_assert_not_reached();
+    }
+
+    s->apb_freq = s->hpll / (SCU_CLK_GET_PCLK_DIV(s->regs[CLK_SEL]) + 1)
+        / apb_divider;
+}
+
 static uint64_t aspeed_scu_read(void *opaque, hwaddr offset, unsigned size)
 {
     AspeedSCUState *s = ASPEED_SCU(opaque);
@@ -222,6 +243,10 @@ static void aspeed_scu_write(void *opaque, hwaddr offset, uint64_t data,
     case PROT_KEY:
         s->regs[reg] = (data == ASPEED_SCU_PROT_KEY) ? 1 : 0;
         return;
+    case CLK_SEL:
+        s->regs[reg] = data;
+        aspeed_scu_set_apb_freq(s);
+        break;
 
     case FREQ_CNTR_EVAL:
     case VGA_SCRATCH1 ... VGA_SCRATCH8:
@@ -247,19 +272,93 @@ static const MemoryRegionOps aspeed_scu_ops = {
     .valid.unaligned = false,
 };
 
+static uint32_t aspeed_scu_get_clkin(AspeedSCUState *s)
+{
+    if (s->hw_strap1 & SCU_HW_STRAP_CLK_25M_IN) {
+        return 25000000;
+    } else if (s->hw_strap1 & SCU_HW_STRAP_CLK_48M_IN) {
+        return 48000000;
+    } else {
+        return 24000000;
+    }
+}
+
+/*
+ * Strapped frequencies for the AST2400 in MHz. They depend on the
+ * clkin frequency.
+ */
+static const uint32_t hpll_ast2400_freqs[][4] = {
+    { 384, 360, 336, 408 }, /* 24MHz or 48MHz */
+    { 400, 375, 350, 425 }, /* 25MHz */
+};
+
+static uint32_t aspeed_scu_calc_hpll_ast2400(AspeedSCUState *s)
+{
+    uint32_t hpll_reg = s->regs[HPLL_PARAM];
+    uint8_t freq_select;
+    bool clk_25m_in;
+
+    if (hpll_reg & SCU_AST2400_H_PLL_OFF) {
+        return 0;
+    }
+
+    if (hpll_reg & SCU_AST2400_H_PLL_PROGRAMMED) {
+        uint32_t multiplier = 1;
+
+        if (!(hpll_reg & SCU_AST2400_H_PLL_BYPASS_EN)) {
+            uint32_t n  = (hpll_reg >> 5) & 0x3f;
+            uint32_t od = (hpll_reg >> 4) & 0x1;
+            uint32_t d  = hpll_reg & 0xf;
+
+            multiplier = (2 - od) * ((n + 2) / (d + 1));
+        }
+
+        return s->clkin * multiplier;
+    }
+
+    /* HW strapping */
+    clk_25m_in = (s->hw_strap1 & SCU_HW_STRAP_CLK_25M_IN);
+    freq_select = SCU_AST2400_HW_STRAP_GET_H_PLL_CLK(s->hw_strap1);
+
+    return hpll_ast2400_freqs[clk_25m_in][freq_select] * 1000000;
+}
+
+static uint32_t aspeed_scu_calc_hpll_ast2500(AspeedSCUState *s)
+{
+    uint32_t hpll_reg   = s->regs[HPLL_PARAM];
+    uint32_t multiplier = 1;
+
+    if (hpll_reg & SCU_H_PLL_OFF) {
+        return 0;
+    }
+
+    if (!(hpll_reg & SCU_H_PLL_BYPASS_EN)) {
+        uint32_t p = (hpll_reg >> 13) & 0x3f;
+        uint32_t m = (hpll_reg >> 5) & 0xff;
+        uint32_t n = hpll_reg & 0x1f;
+
+        multiplier = ((m + 1) / (n + 1)) / (p + 1);
+    }
+
+    return s->clkin * multiplier;
+}
+
 static void aspeed_scu_reset(DeviceState *dev)
 {
     AspeedSCUState *s = ASPEED_SCU(dev);
     const uint32_t *reset;
+    uint32_t (*calc_hpll)(AspeedSCUState *s);
 
     switch (s->silicon_rev) {
     case AST2400_A0_SILICON_REV:
     case AST2400_A1_SILICON_REV:
         reset = ast2400_a0_resets;
+        calc_hpll = aspeed_scu_calc_hpll_ast2400;
         break;
     case AST2500_A0_SILICON_REV:
     case AST2500_A1_SILICON_REV:
         reset = ast2500_a1_resets;
+        calc_hpll = aspeed_scu_calc_hpll_ast2500;
         break;
     default:
         g_assert_not_reached();
@@ -270,6 +369,13 @@ static void aspeed_scu_reset(DeviceState *dev)
     s->regs[HW_STRAP1] = s->hw_strap1;
     s->regs[HW_STRAP2] = s->hw_strap2;
     s->regs[PROT_KEY] = s->hw_prot_key;
+
+    /*
+     * All registers are set. Now compute the frequencies of the main clocks
+     */
+    s->clkin = aspeed_scu_get_clkin(s);
+    s->hpll = calc_hpll(s);
+    aspeed_scu_set_apb_freq(s);
 }
 
 static uint32_t aspeed_silicon_revs[] = {
-- 
2.13.6