Re: [PATCH v2] MIPS: ralink: fix cpu clock of mt7621 and add dt clk devices

[NeilBrown <neil@brown.name>]

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On Thu, Mar 21 2019, Chuanhong Guo wrote:

> For a long time the mt7621 uses a fixed cpu clock which causes a problem
> if the cpu frequency is not 880MHz.
>
> This patch fixes the cpu clock calculation and adds the cpu/bus clkdev
> which will be used in dts.
>
> Signed-off-by: Weijie Gao <hackpascal@gmail.com>
>
> Ported from OpenWrt:
> c7ca224299 ramips: fix cpu clock of mt7621 and add dt clk devices
>
> Signed-off-by: Chuanhong Guo <gch981213@gmail.com>

Thanks for posting this.
I've been using this patch on my mt7621 board (gnubee NAS) for a while
and it is much better than having to specify the clock speed in the DTS
file.
  Tested-by: NeilBrown <neil@brown.name>

Thanks,
NeilBrown


> ---
>
> Change since v1:
>  Correctly fix the following checkpatch.pl warning:
>  WARNING: Missing a blank line after declarations
>  #137: FILE: arch/mips/ralink/mt7621.c:146:
>  +	u32 xtal_clk, cpu_clk, bus_clk;
>  +	const static u32 prediv_tbl[] = {0, 1, 2, 2};
>
>  arch/mips/include/asm/mach-ralink/mt7621.h |  20 ++++
>  arch/mips/ralink/mt7621.c                  | 102 ++++++++++++++-------
>  arch/mips/ralink/timer-gic.c               |   4 +-
>  3 files changed, 93 insertions(+), 33 deletions(-)
>
> diff --git a/arch/mips/include/asm/mach-ralink/mt7621.h b/arch/mips/include/asm/mach-ralink/mt7621.h
> index a672e06fa5fd..b8a8834164c8 100644
> --- a/arch/mips/include/asm/mach-ralink/mt7621.h
> +++ b/arch/mips/include/asm/mach-ralink/mt7621.h
> @@ -19,6 +19,10 @@
>  #define SYSC_REG_CHIP_REV		0x0c
>  #define SYSC_REG_SYSTEM_CONFIG0		0x10
>  #define SYSC_REG_SYSTEM_CONFIG1		0x14
> +#define SYSC_REG_CLKCFG0		0x2c
> +#define SYSC_REG_CUR_CLK_STS		0x44
> +
> +#define MEMC_REG_CPU_PLL		0x648
>  
>  #define CHIP_REV_PKG_MASK		0x1
>  #define CHIP_REV_PKG_SHIFT		16
> @@ -26,6 +30,22 @@
>  #define CHIP_REV_VER_SHIFT		8
>  #define CHIP_REV_ECO_MASK		0xf
>  
> +#define XTAL_MODE_SEL_MASK		0x7
> +#define XTAL_MODE_SEL_SHIFT		6
> +
> +#define CPU_CLK_SEL_MASK		0x3
> +#define CPU_CLK_SEL_SHIFT		30
> +
> +#define CUR_CPU_FDIV_MASK		0x1f
> +#define CUR_CPU_FDIV_SHIFT		8
> +#define CUR_CPU_FFRAC_MASK		0x1f
> +#define CUR_CPU_FFRAC_SHIFT		0
> +
> +#define CPU_PLL_PREDIV_MASK		0x3
> +#define CPU_PLL_PREDIV_SHIFT		12
> +#define CPU_PLL_FBDIV_MASK		0x7f
> +#define CPU_PLL_FBDIV_SHIFT		4
> +
>  #define MT7621_DRAM_BASE                0x0
>  #define MT7621_DDR2_SIZE_MIN		32
>  #define MT7621_DDR2_SIZE_MAX		256
> diff --git a/arch/mips/ralink/mt7621.c b/arch/mips/ralink/mt7621.c
> index d2718de60b9b..6828eefb0a85 100644
> --- a/arch/mips/ralink/mt7621.c
> +++ b/arch/mips/ralink/mt7621.c
> @@ -9,22 +9,22 @@
>  
>  #include <linux/kernel.h>
>  #include <linux/init.h>
> +#include <linux/clk.h>
> +#include <linux/clkdev.h>
> +#include <linux/clk-provider.h>
> +#include <dt-bindings/clock/mt7621-clk.h>
>  
>  #include <asm/mipsregs.h>
>  #include <asm/smp-ops.h>
>  #include <asm/mips-cps.h>
>  #include <asm/mach-ralink/ralink_regs.h>
>  #include <asm/mach-ralink/mt7621.h>
> +#include <asm/time.h>
>  
>  #include <pinmux.h>
>  
>  #include "common.h"
>  
> -#define SYSC_REG_SYSCFG		0x10
> -#define SYSC_REG_CPLL_CLKCFG0	0x2c
> -#define SYSC_REG_CUR_CLK_STS	0x44
> -#define CPU_CLK_SEL		(BIT(30) | BIT(31))
> -
>  #define MT7621_GPIO_MODE_UART1		1
>  #define MT7621_GPIO_MODE_I2C		2
>  #define MT7621_GPIO_MODE_UART3_MASK	0x3
> @@ -110,49 +110,89 @@ static struct rt2880_pmx_group mt7621_pinmux_data[] = {
>  	{ 0 }
>  };
>  
> +static struct clk *clks[MT7621_CLK_MAX];
> +static struct clk_onecell_data clk_data = {
> +	.clks = clks,
> +	.clk_num = ARRAY_SIZE(clks),
> +};
> +
>  phys_addr_t mips_cpc_default_phys_base(void)
>  {
>  	panic("Cannot detect cpc address");
>  }
>  
> +static struct clk *__init mt7621_add_sys_clkdev(
> +	const char *id, unsigned long rate)
> +{
> +	struct clk *clk;
> +	int err;
> +
> +	clk = clk_register_fixed_rate(NULL, id, NULL, 0, rate);
> +	if (IS_ERR(clk))
> +		panic("failed to allocate %s clock structure", id);
> +
> +	err = clk_register_clkdev(clk, id, NULL);
> +	if (err)
> +		panic("unable to register %s clock device", id);
> +
> +	return clk;
> +}
> +
>  void __init ralink_clk_init(void)
>  {
> -	int cpu_fdiv = 0;
> -	int cpu_ffrac = 0;
> -	int fbdiv = 0;
> -	u32 clk_sts, syscfg;
> -	u8 clk_sel = 0, xtal_mode;
> -	u32 cpu_clk;
> +	const static u32 prediv_tbl[] = {0, 1, 2, 2};
> +	u32 syscfg, xtal_sel, clkcfg, clk_sel, curclk, ffiv, ffrac;
> +	u32 pll, prediv, fbdiv;
> +	u32 xtal_clk, cpu_clk, bus_clk;
> +
> +	syscfg = rt_sysc_r32(SYSC_REG_SYSTEM_CONFIG0);
> +	xtal_sel = (syscfg >> XTAL_MODE_SEL_SHIFT) & XTAL_MODE_SEL_MASK;
>  
> -	if ((rt_sysc_r32(SYSC_REG_CPLL_CLKCFG0) & CPU_CLK_SEL) != 0)
> -		clk_sel = 1;
> +	clkcfg = rt_sysc_r32(SYSC_REG_CLKCFG0);
> +	clk_sel = (clkcfg >> CPU_CLK_SEL_SHIFT) & CPU_CLK_SEL_MASK;
> +
> +	curclk = rt_sysc_r32(SYSC_REG_CUR_CLK_STS);
> +	ffiv = (curclk >> CUR_CPU_FDIV_SHIFT) & CUR_CPU_FDIV_MASK;
> +	ffrac = (curclk >> CUR_CPU_FFRAC_SHIFT) & CUR_CPU_FFRAC_MASK;
> +
> +	if (xtal_sel <= 2)
> +		xtal_clk = 20 * 1000 * 1000;
> +	else if (xtal_sel <= 5)
> +		xtal_clk = 40 * 1000 * 1000;
> +	else
> +		xtal_clk = 25 * 1000 * 1000;
>  
>  	switch (clk_sel) {
>  	case 0:
> -		clk_sts = rt_sysc_r32(SYSC_REG_CUR_CLK_STS);
> -		cpu_fdiv = ((clk_sts >> 8) & 0x1F);
> -		cpu_ffrac = (clk_sts & 0x1F);
> -		cpu_clk = (500 * cpu_ffrac / cpu_fdiv) * 1000 * 1000;
> +		cpu_clk = 500 * 1000 * 1000;
>  		break;
> -
>  	case 1:
> -		fbdiv = ((rt_sysc_r32(0x648) >> 4) & 0x7F) + 1;
> -		syscfg = rt_sysc_r32(SYSC_REG_SYSCFG);
> -		xtal_mode = (syscfg >> 6) & 0x7;
> -		if (xtal_mode >= 6) {
> -			/* 25Mhz Xtal */
> -			cpu_clk = 25 * fbdiv * 1000 * 1000;
> -		} else if (xtal_mode >= 3) {
> -			/* 40Mhz Xtal */
> -			cpu_clk = 40 * fbdiv * 1000 * 1000;
> -		} else {
> -			/* 20Mhz Xtal */
> -			cpu_clk = 20 * fbdiv * 1000 * 1000;
> -		}
> +		pll = rt_memc_r32(MEMC_REG_CPU_PLL);
> +		fbdiv = (pll >> CPU_PLL_FBDIV_SHIFT) & CPU_PLL_FBDIV_MASK;
> +		prediv = (pll >> CPU_PLL_PREDIV_SHIFT) & CPU_PLL_PREDIV_MASK;
> +		cpu_clk = ((fbdiv + 1) * xtal_clk) >> prediv_tbl[prediv];
>  		break;
> +	default:
> +		cpu_clk = xtal_clk;
>  	}
> +
> +	cpu_clk = cpu_clk / ffiv * ffrac;
> +	bus_clk = cpu_clk / 4;
> +
> +	clks[MT7621_CLK_CPU] = mt7621_add_sys_clkdev("cpu", cpu_clk);
> +	clks[MT7621_CLK_BUS] = mt7621_add_sys_clkdev("bus", bus_clk);
> +
> +	pr_info("CPU Clock: %dMHz\n", cpu_clk / 1000000);
> +	mips_hpt_frequency = cpu_clk / 2;
>  }
>  
> +static void __init mt7621_clocks_init_dt(struct device_node *np)
> +{
> +	of_clk_add_provider(np, of_clk_src_onecell_get, &clk_data);
> +}
> +
> +CLK_OF_DECLARE(mt7621_clk, "mediatek,mt7621-pll", mt7621_clocks_init_dt);
> +
>  void __init ralink_of_remap(void)
>  {
>  	rt_sysc_membase = plat_of_remap_node("mtk,mt7621-sysc");
> diff --git a/arch/mips/ralink/timer-gic.c b/arch/mips/ralink/timer-gic.c
> index b5f07d21fcf2..4fed842ae8eb 100644
> --- a/arch/mips/ralink/timer-gic.c
> +++ b/arch/mips/ralink/timer-gic.c
> @@ -11,14 +11,14 @@
>  
>  #include <linux/of.h>
>  #include <linux/clk-provider.h>
> -#include <linux/clocksource.h>
> +#include <asm/time.h>
>  
>  #include "common.h"
>  
>  void __init plat_time_init(void)
>  {
>  	ralink_of_remap();
> -
> +	ralink_clk_init();
>  	of_clk_init(NULL);
>  	timer_probe();
>  }
> -- 
> 2.21.0

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