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clk: mxs: Fix invalid 32-bit access to frac registers 

According to i.MX23 and i.MX28 reference manual [1],[2] the fractional
clock control register is 32-bit wide, but is separated in 4 parts.
So write instructions must not apply to more than 1 part at once.

The clk init for the i.MX28 violates this restriction and all the other
accesses on that register suggest that there isn't such a restriction.

This patch restricts the access to this register to byte instructions and
extends the comment in the init functions.

Btw the imx23 init now uses a R-M-W sequence just like imx28 init
to avoid any clock glitches.

The changes has been tested with a i.MX23 and a i.MX28 board.

[1] - http://cache.freescale.com/files/dsp/doc/ref_manual/IMX23RM.pdf
[2] - http://cache.freescale.com/files/dsp/doc/ref_manual/MCIMX28RM.pdf

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Michael Turquette <mturquette@linaro.org>
hifive-unleashed-5.1
Stefan Wahren 2015-01-30 19:20:10 +00:00 committed by Michael Turquette
parent 6793a30a06
commit 039e597075
3 changed files with 31 additions and 18 deletions
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11
drivers/clk/mxs/clk-imx23.c
View File

@ -46,11 +46,13 @@ static void __iomem *digctrl;
#define BP_CLKSEQ_BYPASS_SAIF 0
#define BP_CLKSEQ_BYPASS_SSP 5
#define BP_SAIF_DIV_FRAC_EN 16
#define BP_FRAC_IOFRAC 24
#define FRAC_IO 3
static void __init clk_misc_init(void)
{
u32 val;
u8 frac;
/* Gate off cpu clock in WFI for power saving */
writel_relaxed(1 << BP_CPU_INTERRUPT_WAIT, CPU + SET);
@ -72,9 +74,12 @@ static void __init clk_misc_init(void)
/*
* 480 MHz seems too high to be ssp clock source directly,
* so set frac to get a 288 MHz ref_io.
* According to reference manual we must access frac bytewise.
*/
writel_relaxed(0x3f << BP_FRAC_IOFRAC, FRAC + CLR);
writel_relaxed(30 << BP_FRAC_IOFRAC, FRAC + SET);
frac = readb_relaxed(FRAC + FRAC_IO);
frac &= ~0x3f;
frac |= 30;
writeb_relaxed(frac, FRAC + FRAC_IO);
}
static const char *sel_pll[] __initconst = { "pll", "ref_xtal", };

19
drivers/clk/mxs/clk-imx28.c
View File

@ -53,8 +53,9 @@ static void __iomem *clkctrl;
#define BP_ENET_SLEEP 31
#define BP_CLKSEQ_BYPASS_SAIF0 0
#define BP_CLKSEQ_BYPASS_SSP0 3
#define BP_FRAC0_IO1FRAC 16
#define BP_FRAC0_IO0FRAC 24
#define FRAC0_IO1 2
#define FRAC0_IO0 3
static void __iomem *digctrl;
#define DIGCTRL digctrl
@ -85,6 +86,7 @@ int mxs_saif_clkmux_select(unsigned int clkmux)
static void __init clk_misc_init(void)
{
u32 val;
u8 frac;
/* Gate off cpu clock in WFI for power saving */
writel_relaxed(1 << BP_CPU_INTERRUPT_WAIT, CPU + SET);
@ -118,11 +120,16 @@ static void __init clk_misc_init(void)
/*
* 480 MHz seems too high to be ssp clock source directly,
* so set frac0 to get a 288 MHz ref_io0 and ref_io1.
* According to reference manual we must access frac0 bytewise.
*/
val = readl_relaxed(FRAC0);
val &= ~((0x3f << BP_FRAC0_IO0FRAC) | (0x3f << BP_FRAC0_IO1FRAC));
val |= (30 << BP_FRAC0_IO0FRAC) | (30 << BP_FRAC0_IO1FRAC);
writel_relaxed(val, FRAC0);
frac = readb_relaxed(FRAC0 + FRAC0_IO0);
frac &= ~0x3f;
frac |= 30;
writeb_relaxed(frac, FRAC0 + FRAC0_IO0);
frac = readb_relaxed(FRAC0 + FRAC0_IO1);
frac &= ~0x3f;
frac |= 30;
writeb_relaxed(frac, FRAC0 + FRAC0_IO1);
}
static const char *sel_cpu[] __initconst = { "ref_cpu", "ref_xtal", };

19
drivers/clk/mxs/clk-ref.c
View File

@ -16,6 +16,8 @@
#include <linux/slab.h>
#include "clk.h"
#define BF_CLKGATE BIT(7)
/**
* struct clk_ref - mxs reference clock
* @hw: clk_hw for the reference clock
@ -39,7 +41,7 @@ static int clk_ref_enable(struct clk_hw *hw)
{
struct clk_ref *ref = to_clk_ref(hw);
writel_relaxed(1 << ((ref->idx + 1) * 8 - 1), ref->reg + CLR);
writeb_relaxed(BF_CLKGATE, ref->reg + ref->idx + CLR);
return 0;
}
@ -48,7 +50,7 @@ static void clk_ref_disable(struct clk_hw *hw)
{
struct clk_ref *ref = to_clk_ref(hw);
writel_relaxed(1 << ((ref->idx + 1) * 8 - 1), ref->reg + SET);
writeb_relaxed(BF_CLKGATE, ref->reg + ref->idx + SET);
}
static unsigned long clk_ref_recalc_rate(struct clk_hw *hw,
@ -56,7 +58,7 @@ static unsigned long clk_ref_recalc_rate(struct clk_hw *hw,
{
struct clk_ref *ref = to_clk_ref(hw);
u64 tmp = parent_rate;
u8 frac = (readl_relaxed(ref->reg) >> (ref->idx * 8)) & 0x3f;
u8 frac = readb_relaxed(ref->reg + ref->idx) & 0x3f;
tmp *= 18;
do_div(tmp, frac);
@ -93,8 +95,7 @@ static int clk_ref_set_rate(struct clk_hw *hw, unsigned long rate,
struct clk_ref *ref = to_clk_ref(hw);
unsigned long flags;
u64 tmp = parent_rate;
u32 val;
u8 frac, shift = ref->idx * 8;
u8 frac, val;
tmp = tmp * 18 + rate / 2;
do_div(tmp, rate);
@ -107,10 +108,10 @@ static int clk_ref_set_rate(struct clk_hw *hw, unsigned long rate,
spin_lock_irqsave(&mxs_lock, flags);
val = readl_relaxed(ref->reg);
val &= ~(0x3f << shift);
val |= frac << shift;
writel_relaxed(val, ref->reg);
val = readb_relaxed(ref->reg + ref->idx);
val &= ~0x3f;
val |= frac;
writeb_relaxed(val, ref->reg + ref->idx);
spin_unlock_irqrestore(&mxs_lock, flags);