clk: qoriq: Don't allow CPU clocks higher than starting value

Commit Message

Crystal Wood Oct. 17, 2016, 6:42 p.m. UTC

The boot-time frequency of a CPU is considered its rated maximum, as we
have no other source of such information.  However, this was previously
only used for chips with 80% restrictions on secondary PLLs.  This
usually wasn't a problem because most chips/configs boot with a divider
of /1, with other dividers being used only for dynamic frequency
reduction.  However, at least one config (LS1021A at less than 1 GHz)
uses a different divider for top speed.  This was causing cpufreq to set
a frequency beyond the chip's rated speed.

This is fixed by applying a 100%-of-initial-speed limit to all CPU PLLs,
similar to the existing 80% limit that only applied to some.

Signed-off-by: Scott Wood <[e-mail]>
Cc: [e-mail]
---
 drivers/clk/clk-qoriq.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

Comments

Stephen Boyd Nov. 2, 2016, 12:27 a.m. UTC | #1

On 10/17, Scott Wood wrote:
> The boot-time frequency of a CPU is considered its rated maximum, as we
> have no other source of such information.  However, this was previously
> only used for chips with 80% restrictions on secondary PLLs.  This
> usually wasn't a problem because most chips/configs boot with a divider
> of /1, with other dividers being used only for dynamic frequency
> reduction.  However, at least one config (LS1021A at less than 1 GHz)
> uses a different divider for top speed.  This was causing cpufreq to set
> a frequency beyond the chip's rated speed.
> 
> This is fixed by applying a 100%-of-initial-speed limit to all CPU PLLs,
> similar to the existing 80% limit that only applied to some.
> 
> Signed-off-by: Scott Wood <[e-mail]>
> Cc: [e-mail]
> ---

All silence, so I applied to clk-fixes because presumably this is
some sort of badness we need to fix quickly.

Patch

diff --git a/drivers/clk/clk-qoriq.c b/drivers/clk/clk-qoriq.c
index 20b1055..80ae2a5 100644
--- a/drivers/clk/clk-qoriq.c
+++ b/drivers/clk/clk-qoriq.c
@@ -700,6 +700,7 @@  static struct clk * __init create_mux_common(struct clockgen *cg,
 					     struct mux_hwclock *hwc,
 					     const struct clk_ops *ops,
 					     unsigned long min_rate,
+					     unsigned long max_rate,
 					     unsigned long pct80_rate,
 					     const char *fmt, int idx)
 {
@@ -728,6 +729,8 @@  static struct clk * __init create_mux_common(struct clockgen *cg,
 			continue;
 		if (rate < min_rate)
 			continue;
+		if (rate > max_rate)
+			continue;
 
 		parent_names[j] = div->name;
 		hwc->parent_to_clksel[j] = i;
@@ -759,7 +762,7 @@  static struct clk * __init create_one_cmux(struct clockgen *cg, int idx)
 	struct mux_hwclock *hwc;
 	const struct clockgen_pll_div *div;
 	unsigned long plat_rate, min_rate;
-	u64 pct80_rate;
+	u64 max_rate, pct80_rate;
 	u32 clksel;
 
 	hwc = kzalloc(sizeof(*hwc), GFP_KERNEL);
@@ -787,8 +790,8 @@  static struct clk * __init create_one_cmux(struct clockgen *cg, int idx)
 		return NULL;
 	}
 
-	pct80_rate = clk_get_rate(div->clk);
-	pct80_rate *= 8;
+	max_rate = clk_get_rate(div->clk);
+	pct80_rate = max_rate * 8;
 	do_div(pct80_rate, 10);
 
 	plat_rate = clk_get_rate(cg->pll[PLATFORM_PLL].div[PLL_DIV1].clk);
@@ -798,7 +801,7 @@  static struct clk * __init create_one_cmux(struct clockgen *cg, int idx)
 	else
 		min_rate = plat_rate / 2;
 
-	return create_mux_common(cg, hwc, &cmux_ops, min_rate,
+	return create_mux_common(cg, hwc, &cmux_ops, min_rate, max_rate,
 				 pct80_rate, "cg-cmux%d", idx);
 }
 
@@ -813,7 +816,7 @@  static struct clk * __init create_one_hwaccel(struct clockgen *cg, int idx)
 	hwc->reg = cg->regs + 0x20 * idx + 0x10;
 	hwc->info = cg->info.hwaccel[idx];
 
-	return create_mux_common(cg, hwc, &hwaccel_ops, 0, 0,
+	return create_mux_common(cg, hwc, &hwaccel_ops, 0, ULONG_MAX, 0,
 				 "cg-hwaccel%d", idx);
 }