diff mbox

[02/11] clk: imx: correct AV PLL rate formula

Message ID 1465396420-27064-2-git-send-email-aisheng.dong@nxp.com (mailing list archive)
State Not Applicable, archived
Headers show

Commit Message

Aisheng Dong June 8, 2016, 2:33 p.m. UTC 
From: Anson Huang <b20788@freescale.com>

The audio/video PLL's rate calculation is as below in RM:

Fref * (DIV_SELECT + NUM / DENOM), in origin clk-pllv3's
code, below code is used:

(parent_rate * div) + ((parent_rate / mfd) * mfn

as it does NOT consider the float data using div, so below
formula should be used as a decent method:

(parent_rate * div) + ((parent_rate * mfn) / mfd)

and we also need to consider parent_rate * mfd may overflow
a 32 bit value, 64 bit value should be used.

After updating this formula, the dram PLL's rate is
1066MHz, which is correct, while the old formula gets
1056MHz.

[Aisheng: fix clk_pllv3_av_round_rate too]

Signed-off-by: Anson Huang <b20788@freescale.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
---
 drivers/clk/imx/clk-pllv3.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Shawn Guo June 12, 2016, 11:30 a.m. UTC | #1 
On Wed, Jun 08, 2016 at 10:33:31PM +0800, Dong Aisheng wrote:
> From: Anson Huang <b20788@freescale.com>
> 
> The audio/video PLL's rate calculation is as below in RM:
> 
> Fref * (DIV_SELECT + NUM / DENOM), in origin clk-pllv3's
> code, below code is used:
> 
> (parent_rate * div) + ((parent_rate / mfd) * mfn
> 
> as it does NOT consider the float data using div, so below
> formula should be used as a decent method:
> 
> (parent_rate * div) + ((parent_rate * mfn) / mfd)
> 
> and we also need to consider parent_rate * mfd may overflow
> a 32 bit value, 64 bit value should be used.
> 
> After updating this formula, the dram PLL's rate is
> 1066MHz, which is correct, while the old formula gets
> 1056MHz.
> 
> [Aisheng: fix clk_pllv3_av_round_rate too]
> 
> Signed-off-by: Anson Huang <b20788@freescale.com>
> Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>

Applied, thanks.
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diff mbox

Patch

diff --git a/drivers/clk/imx/clk-pllv3.c b/drivers/clk/imx/clk-pllv3.c
index 44d294a336f0..eea2b1b3791e 100644
--- a/drivers/clk/imx/clk-pllv3.c
+++ b/drivers/clk/imx/clk-pllv3.c
@@ -218,8 +218,12 @@  static unsigned long clk_pllv3_av_recalc_rate(struct clk_hw *hw,
 	u32 mfn = readl_relaxed(pll->base + PLL_NUM_OFFSET);
 	u32 mfd = readl_relaxed(pll->base + PLL_DENOM_OFFSET);
 	u32 div = readl_relaxed(pll->base) & pll->div_mask;
+	u64 temp64 = (u64)parent_rate;
 
-	return (parent_rate * div) + ((parent_rate / mfd) * mfn);
+	temp64 *= mfn;
+	do_div(temp64, mfd);
+
+	return (parent_rate * div) + (u32)temp64;
 }
 
 static long clk_pllv3_av_round_rate(struct clk_hw *hw, unsigned long rate,
@@ -243,7 +247,7 @@  static long clk_pllv3_av_round_rate(struct clk_hw *hw, unsigned long rate,
 	do_div(temp64, parent_rate);
 	mfn = temp64;
 
-	return parent_rate * div + parent_rate / mfd * mfn;
+	return parent_rate * div + parent_rate * mfn / mfd;
 }
 
 static int clk_pllv3_av_set_rate(struct clk_hw *hw, unsigned long rate,