linux-kernel - Re: [PATCH 2/2] clocksource: timer-imx-sysctr: support i.MX95

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Message-ID: <20240123095241.66nrgkkrdth6g32w@pengutronix.de>
Date: Tue, 23 Jan 2024 10:52:41 +0100
From: Marco Felsch <m.felsch@...gutronix.de>
To: "Peng Fan (OSS)" <peng.fan@....nxp.com>
Cc: daniel.lezcano@...aro.org, tglx@...utronix.de, robh+dt@...nel.org,
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
	shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
	linux-imx@....com, devicetree@...r.kernel.org,
	Peng Fan <peng.fan@....com>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] clocksource: timer-imx-sysctr: support i.MX95

Hi Peng,

On 24-01-22, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@....com>
> 
> To i.MX95 System counter module, we use Read register space to get
> the counter, not the Control register space to get the counter, because
> System Manager firmware not allow Linux to read Control register space.
> 
> Signed-off-by: Peng Fan <peng.fan@....com>
> ---
>  drivers/clocksource/timer-imx-sysctr.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/clocksource/timer-imx-sysctr.c b/drivers/clocksource/timer-imx-sysctr.c
> index 5a7a951c4efc..3d3bc16388ed 100644
> --- a/drivers/clocksource/timer-imx-sysctr.c
> +++ b/drivers/clocksource/timer-imx-sysctr.c
> @@ -8,9 +8,12 @@
>  #include "timer-of.h"
>  
>  #define CMP_OFFSET	0x10000
> +#define RD_OFFSET	0x20000
>  
>  #define CNTCV_LO	0x8
>  #define CNTCV_HI	0xc
> +#define CNTCV_LO_IMX95	(RD_OFFSET + 0x8)
> +#define CNTCV_HI_IMX95	(RD_OFFSET + 0xc)
>  #define CMPCV_LO	(CMP_OFFSET + 0x20)
>  #define CMPCV_HI	(CMP_OFFSET + 0x24)
>  #define CMPCR		(CMP_OFFSET + 0x2c)
> @@ -22,6 +25,8 @@
>  
>  static void __iomem *sys_ctr_base __ro_after_init;
>  static u32 cmpcr __ro_after_init;
> +static u32 cntcv_hi = CNTCV_HI;
> +static u32 cntcv_lo = CNTCV_LO;
>  
>  static void sysctr_timer_enable(bool enable)
>  {
> @@ -43,9 +48,9 @@ static inline u64 sysctr_read_counter(void)
>  	u32 cnt_hi, tmp_hi, cnt_lo;
>  
>  	do {
> -		cnt_hi = readl_relaxed(sys_ctr_base + CNTCV_HI);
> -		cnt_lo = readl_relaxed(sys_ctr_base + CNTCV_LO);
> -		tmp_hi = readl_relaxed(sys_ctr_base + CNTCV_HI);
> +		cnt_hi = readl_relaxed(sys_ctr_base + cntcv_hi);
> +		cnt_lo = readl_relaxed(sys_ctr_base + cntcv_lo);
> +		tmp_hi = readl_relaxed(sys_ctr_base + cntcv_hi);
>  	} while (tmp_hi != cnt_hi);
>  
>  	return  ((u64) cnt_hi << 32) | cnt_lo;
> @@ -139,6 +144,11 @@ static int __init sysctr_timer_init(struct device_node *np)
>  		to_sysctr.of_clk.rate /= SYS_CTR_CLK_DIV;
>  	}
>  
> +	if (of_device_is_compatible(np, "nxp,imx95-sysctr-timer")) {
> +		cntcv_hi = CNTCV_HI_IMX95;
> +		cntcv_lo = CNTCV_LO_IMX95;
> +	}

I'm not a fan of this, since TIMER_OF_DECLARE() can do the compat check.
So instead of using fallback bindings just use the correct binding
within the dts file. Also I'm not a fan of this clobal variable setting
albeit there is just one instance _yet_ we really should instead rework
this driver a bit and instead provide a i.MX95 specific
sysctr_read_counter() function. This is clearly a bit more work but IMO
a cleaner approach. Also afterwards once you add i.MX9x which is again a
bit different would gain from this work.

Regards,
  Marco

> +
>  	sys_ctr_base = timer_of_base(&to_sysctr);
>  	cmpcr = readl(sys_ctr_base + CMPCR);
>  	cmpcr &= ~SYS_CTR_EN;
> -- 
> 2.37.1
> 
> 
>