cpu/allwinner/a10: Add helper to configure CPU clock

Change-Id: I5a3bb3220aeefdd6822a7dbecf210ff77095dad6
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/4685
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/cpu/allwinner/a10/clock.c

@@ -8,6 +8,10 @@
 #include "clock.h"
 
 #include <arch/io.h>
+#include <console/console.h>
+#include <delay.h>
+#include <lib.h>
+#include <stdlib.h>
 
 static struct a10_ccm *const ccm = (void *)A1X_CCM_BASE;
 
@@ -121,3 +125,154 @@ void a1x_gate_dram_clock_output(void)
 {
 	clrbits_le32(&ccm->dram_clk_cfg, DRAM_CTRL_DCLK_OUT);
 }
+
+/*
+ * Linker doesn't garbage collect and the function below adds about half
+ * kilobyte to the bootblock, and log2_ceil is not available in the bootblock.
+ */
+#ifndef __BOOT_BLOCK__
+
+#define PLL1_CFG(N, K, M, P_EXP)	\
+	((1 << 31 | 0 << 30 | 8 << 26 | 0 << 25 | 16 << 20 | 2 << 13) | \
+	(P_EXP) << 16 |  (N) << 8 | \
+	(K - 1) << 4 | 0 << 3 | 0 << 2 | (M -1) << 0)
+
+static const struct {
+	u32 pll1_cfg;
+	u16 freq_mhz;
+} pll1_table[] = {
+	/* PLL1 output = (24MHz * N * K) / (M * P) */
+	{ PLL1_CFG(16, 1, 1, 0),  384 },
+	{ PLL1_CFG(16, 2, 1, 0),  768 },
+	{ PLL1_CFG(20, 2, 1, 0),  960 },
+	{ PLL1_CFG(21, 2, 1, 0), 1008 },
+	{ PLL1_CFG(22, 2, 1, 0), 1056 },
+	{ PLL1_CFG(23, 2, 1, 0), 1104 },
+	{ PLL1_CFG(24, 2, 1, 0), 1152 },
+	{ PLL1_CFG(25, 2, 1, 0), 1200 },
+	{ PLL1_CFG(26, 2, 1, 0), 1248 },
+	{ PLL1_CFG(27, 2, 1, 0), 1296 },
+	{ PLL1_CFG(28, 2, 1, 0), 1344 },
+	{ PLL1_CFG(29, 2, 1, 0), 1392 },
+	{ PLL1_CFG(30, 2, 1, 0), 1440 },
+	{ PLL1_CFG(31, 2, 1, 0), 1488 },
+	{ PLL1_CFG(20, 4, 1, 0), 1944 },
+};
+
+static inline u32 div_ceil(u32 a, u32 b)
+{
+	return (a + b - 1) / b;
+}
+
+static void cpu_clk_src_switch(u32 clksel_bits)
+{
+	u32 reg32;
+
+	reg32 = read32(&ccm->cpu_ahb_apb0_cfg);
+	reg32 &= ~CPU_CLK_SRC_MASK;
+	reg32 |= clksel_bits & CPU_CLK_SRC_MASK;
+	write32(reg32, &ccm->cpu_ahb_apb0_cfg);
+}
+
+static void change_sys_divisors(u8 axi, u8 ahb_exp, u8 apb0_exp)
+{
+	u32 reg32;
+
+	reg32 = read32(&ccm->cpu_ahb_apb0_cfg);
+	/* Not a typo: We want to keep only the CLK_SRC bits */
+	reg32 &= CPU_CLK_SRC_MASK;
+	reg32 |= ((axi - 1) << 0) & AXI_DIV_MASK;
+	reg32 |= (ahb_exp << 4) & AHB_DIV_MASK;
+	reg32 |= (apb0_exp << 8) & APB0_DIV_MASK;
+	write32(reg32, &ccm->cpu_ahb_apb0_cfg);
+}
+
+static void spin_delay(u32 loops)
+{
+	volatile u32 x = loops;
+	while (x--);
+}
+
+/**
+ * \brief Configure the CPU clock and PLL1
+ *
+ * To run at full speed, the CPU uses PLL1 as the clock source. AXI, AHB, and
+ * APB0 are derived from the CPU clock, and need to be kept within certain
+ * limits. This function configures PLL1 as close as possible to the desired
+ * frequency, based on a set of known working configurations for PLL1. It then
+ * calculates and applies the appropriate divisors for the AXI/AHB/APB0 clocks,
+ * before finally switching the CPU to run from the new clock.
+ * No further configuration of the CPU clock or divisors is needed. after
+ * calling this function.
+ *
+ * @param[in] cpu_clk_mhz Desired CPU clock, in MHz
+ */
+void a1x_set_cpu_clock(u16 cpu_clk_mhz)
+{
+	int i = 0;
+	u8 axi, ahb, ahb_exp, apb0, apb0_exp;
+	u32 actual_mhz;
+
+	/*
+	 * Rated clock for PLL1 is 2000 MHz, but there is no combination of
+	 * parameters that yields that exact frequency. 1944 MHz is the highest.
+	 */
+	if (cpu_clk_mhz > 1944) {
+		printk(BIOS_CRIT, "BUG! maximum PLL1 clock is 1944 MHz,"
+				  "but asked to clock CPU at %d MHz\n",
+				  cpu_clk_mhz);
+		cpu_clk_mhz = 1944;
+	}
+	/* Find target frequency */
+	while (pll1_table[i].freq_mhz < cpu_clk_mhz)
+		i++;
+
+	actual_mhz = pll1_table[i].freq_mhz;
+
+	if (cpu_clk_mhz != actual_mhz) {
+		printk(BIOS_WARNING, "Parameters for %d MHz not available, "
+				     "setting CPU clock at %d MHz\n",
+				     cpu_clk_mhz, actual_mhz);
+	}
+
+	/*
+	 * Calculate system clock divisors:
+	 * The minimum clock divisor for APB0 is 2, which guarantees that AHB0
+	 * will always be in spec, as long as AHB is in spec, although the max
+	 * AHB0 clock we can get is 125 MHz
+	 */
+	axi = div_ceil(actual_mhz, 450);	/* Max 450 MHz */
+	ahb = div_ceil(actual_mhz/axi, 250);	/* Max 250 MHz */
+	apb0 = 2;				/* Max 150 MHz */
+
+	ahb_exp = log2_ceil(ahb);
+	ahb = 1 << ahb_exp;
+	apb0_exp = 1;
+
+	printk(BIOS_INFO, "CPU: %d MHz, AXI %d Mhz, AHB: %d MHz APB0: %d MHz\n",
+			  actual_mhz,
+			  actual_mhz / axi,
+			  actual_mhz / (axi * ahb),
+			  actual_mhz / (axi * ahb * apb0));
+
+	/* Keep the CPU off PLL1 while we change PLL parameters */
+	cpu_clk_src_switch(CPU_CLK_SRC_OSC24M);
+	/*
+	 * We can't use udelay() here. udelay() relies on timer 0, but timers
+	 * have the habit of not ticking when the CPU is clocked from the main
+	 * oscillator.
+	 */
+	spin_delay(8);
+
+	change_sys_divisors(axi, ahb_exp, apb0_exp);
+
+	/* Configure PLL1 at the desired frequency */
+	write32(pll1_table[i].pll1_cfg, &ccm->pll1_cfg);
+	spin_delay(8);
+
+	cpu_clk_src_switch(CPU_CLK_SRC_PLL1);
+	/* Here, we're running from PLL, so timers will tick */
+	udelay(1);
+}
+
+#endif  /* __BOOT_BLOCK__ */

src/cpu/allwinner/a10/clock.h

@@ -256,4 +256,7 @@ void a1x_pll5_enable_dram_clock_output(void);
 void a1x_ungate_dram_clock_output(void);
 void a1x_gate_dram_clock_output(void);
 
+/* Not available in bootblock */
+void a1x_set_cpu_clock(u16 cpu_clk_mhz);
+
 #endif				/* CPU_ALLWINNER_A10_CLOCK_H */