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clk: imx: correct AV PLL rate formula 

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>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
This commit is contained in:
Anson Huang 2016-06-08 22:33:31 +08:00 committed by Shawn Guo
parent 1a695a905c
commit ba7f4f557e
1 changed files with 6 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
drivers/clk/imx/clk-pllv3.c
View File

@ -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,