[PATCH/RFC v3 2/3] ARM: shmobile: sh73a0: add support for adjusting CPU frequency
Guennadi Liakhovetski
g.liakhovetski at gmx.de
Thu Feb 28 07:21:59 EST 2013
On SH73A0 the output of PLL0 is supplied to two dividers, feeding clock to
the CPU core and SGX. Lower CPU frequencies allow the use of lower supply
voltages and thus reduce power consumption.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski at gmx.de>
---
v3:
1. Changed the order of reducing the clock frequency. It turned out, that
sh73a0 behaves differently when switching for the first time from a
disabled Z-clock divisor (pass-through from PLL0) to a higher or to a
lower output frequency. Switching to 1/2 of the input frequency worked
always, whereas switching to 1/3 didn't work for the first time, even
though exactly the same code is used. The reason is probably, that 1/2
division is achieved by writing 0 to the divisor field, which is also the
default value, and 1/3 is set by writing 1. The problem can be fixed by
first enabling the divisor, and then setting the division factor.
2. To make the above safer we now always reset the divisor field to 0,
when disabling the divisor and going to the full PLL0 rate for the
Z-clock.
arch/arm/mach-shmobile/clock-sh73a0.c | 95 ++++++++++++++++++++++++++++++++-
1 files changed, 93 insertions(+), 2 deletions(-)
diff --git a/arch/arm/mach-shmobile/clock-sh73a0.c b/arch/arm/mach-shmobile/clock-sh73a0.c
index 34b5c5a..1108d77 100644
--- a/arch/arm/mach-shmobile/clock-sh73a0.c
+++ b/arch/arm/mach-shmobile/clock-sh73a0.c
@@ -276,6 +276,11 @@ enum { DIV4_I, DIV4_ZG, DIV4_M3, DIV4_B, DIV4_M1, DIV4_M2,
static struct clk div4_clks[DIV4_NR] = {
[DIV4_I] = DIV4(FRQCRA, 20, 0xdff, CLK_ENABLE_ON_INIT),
+ /*
+ * ZG clock is dividing PLL0 frequency to supply SGX. Make sure not to
+ * exceed maximum frequencies of 201.5MHz for VDD_DVFS=1.175 and
+ * 239.2MHz for VDD_DVFS=1.315V.
+ */
[DIV4_ZG] = SH_CLK_DIV4(&pll0_clk, FRQCRA, 16, 0xd7f, CLK_ENABLE_ON_INIT),
[DIV4_M3] = DIV4(FRQCRA, 12, 0x1dff, CLK_ENABLE_ON_INIT),
[DIV4_B] = DIV4(FRQCRA, 8, 0xdff, CLK_ENABLE_ON_INIT),
@@ -288,6 +293,85 @@ static struct clk div4_clks[DIV4_NR] = {
[DIV4_HP] = DIV4(FRQCRB, 4, 0xdff, 0),
};
+static int (*div4_set_rate)(struct clk *clk, unsigned long rate);
+static unsigned long (*div4_recalc)(struct clk *clk);
+static long (*div4_round_rate)(struct clk *clk, unsigned long rate);
+
+static int zclk_set_rate(struct clk *clk, unsigned long rate)
+{
+ int ret;
+
+ if (!clk->parent || !__clk_get(clk->parent))
+ return -ENODEV;
+
+ if (readl(FRQCRB) & (1 << 31))
+ return -EBUSY;
+
+ if (rate == clk_get_rate(clk->parent)) {
+ /* 1:1 - switch off divider */
+ __raw_writel(__raw_readl(FRQCRB) & ~(1 << 28), FRQCRB);
+ /* nullify the divider to prepare for the next time */
+ ret = div4_set_rate(clk, rate / 2);
+ if (!ret)
+ ret = frqcr_kick();
+ if (ret > 0)
+ ret = 0;
+ } else {
+ /* Enable the divider */
+ __raw_writel(__raw_readl(FRQCRB) | (1 << 28), FRQCRB);
+
+ ret = frqcr_kick();
+ if (ret >= 0)
+ /*
+ * set the divider - call the DIV4 method, it will kick
+ * FRQCRB too
+ */
+ ret = div4_set_rate(clk, rate);
+ if (ret < 0)
+ goto esetrate;
+ }
+
+esetrate:
+ __clk_put(clk->parent);
+ return ret;
+}
+
+static long zclk_round_rate(struct clk *clk, unsigned long rate)
+{
+ unsigned long div_freq = div4_round_rate(clk, rate),
+ parent_freq = clk_get_rate(clk->parent);
+
+ if (rate > div_freq && abs(parent_freq - rate) < rate - div_freq)
+ return parent_freq;
+
+ return div_freq;
+}
+
+static unsigned long zclk_recalc(struct clk *clk)
+{
+ /*
+ * Must recalculate frequencies in case PLL0 has been changed, even if
+ * the divisor is unused ATM!
+ */
+ unsigned long div_freq = div4_recalc(clk);
+
+ if (__raw_readl(FRQCRB) & (1 << 28))
+ return div_freq;
+
+ return clk_get_rate(clk->parent);
+}
+
+static void zclk_extend(void)
+{
+ /* We extend the DIV4 clock with a 1:1 pass-through case */
+ div4_set_rate = div4_clks[DIV4_Z].ops->set_rate;
+ div4_round_rate = div4_clks[DIV4_Z].ops->round_rate;
+ div4_recalc = div4_clks[DIV4_Z].ops->recalc;
+ div4_clks[DIV4_Z].ops->set_rate = zclk_set_rate;
+ div4_clks[DIV4_Z].ops->round_rate = zclk_round_rate;
+ div4_clks[DIV4_Z].ops->recalc = zclk_recalc;
+}
+
enum { DIV6_VCK1, DIV6_VCK2, DIV6_VCK3, DIV6_ZB1,
DIV6_FLCTL, DIV6_SDHI0, DIV6_SDHI1, DIV6_SDHI2,
DIV6_FSIA, DIV6_FSIB, DIV6_SUB,
@@ -485,7 +569,7 @@ static struct clk *late_main_clks[] = {
};
enum { MSTP001,
- MSTP129, MSTP128, MSTP127, MSTP126, MSTP125, MSTP118, MSTP116, MSTP100,
+ MSTP129, MSTP128, MSTP127, MSTP126, MSTP125, MSTP118, MSTP116, MSTP112, MSTP100,
MSTP219, MSTP218, MSTP217,
MSTP207, MSTP206, MSTP204, MSTP203, MSTP202, MSTP201, MSTP200,
MSTP331, MSTP329, MSTP328, MSTP325, MSTP323, MSTP322,
@@ -506,6 +590,7 @@ static struct clk mstp_clks[MSTP_NR] = {
[MSTP125] = MSTP(&div6_clks[DIV6_SUB], SMSTPCR1, 25, 0), /* TMU0 */
[MSTP118] = MSTP(&div4_clks[DIV4_B], SMSTPCR1, 18, 0), /* DSITX0 */
[MSTP116] = MSTP(&div4_clks[DIV4_HP], SMSTPCR1, 16, 0), /* IIC0 */
+ [MSTP112] = MSTP(&div4_clks[DIV4_ZG], SMSTPCR1, 12, 0), /* SGX */
[MSTP100] = MSTP(&div4_clks[DIV4_B], SMSTPCR1, 0, 0), /* LCDC0 */
[MSTP219] = MSTP(&div6_clks[DIV6_SUB], SMSTPCR2, 19, 0), /* SCIFA7 */
[MSTP218] = MSTP(&div4_clks[DIV4_HP], SMSTPCR2, 18, 0), /* SY-DMAC */
@@ -547,6 +632,9 @@ static struct clk_lookup lookups[] = {
/* main clocks */
CLKDEV_CON_ID("r_clk", &r_clk),
+ /* DIV4 clocks */
+ CLKDEV_DEV_ID("cpu0", &div4_clks[DIV4_Z]), /* cpufreq-cpu0 */
+
/* DIV6 clocks */
CLKDEV_CON_ID("vck1_clk", &div6_clks[DIV6_VCK1]),
CLKDEV_CON_ID("vck2_clk", &div6_clks[DIV6_VCK2]),
@@ -638,8 +726,11 @@ void __init sh73a0_clock_init(void)
for (k = 0; !ret && (k < ARRAY_SIZE(main_clks)); k++)
ret = clk_register(main_clks[k]);
- if (!ret)
+ if (!ret) {
ret = sh_clk_div4_register(div4_clks, DIV4_NR, &div4_table);
+ if (!ret)
+ zclk_extend();
+ }
if (!ret)
ret = sh_clk_div6_reparent_register(div6_clks, DIV6_NR);
--
1.7.2.5
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