linux-kernel - Re: [PATCH v6 6/6] cpufreq: ti-cpufreq: Update efuse/rev offsets in AM62 family

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Message-ID: <809b9eaa-a539-4309-95a3-c9fc9c39288b@ti.com>
Date: Wed, 25 Sep 2024 11:12:52 -0500
From: Andrew Davis <afd@...com>
To: Dhruva Gole <d-gole@...com>, Nishanth Menon <nm@...com>,
        Vignesh
 Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>, Rob Herring
	<robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
	<conor+dt@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar
	<viresh.kumar@...aro.org>
CC: <linux-arm-kernel@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
        Bryan Brattlof
	<bb@...com>
Subject: Re: [PATCH v6 6/6] cpufreq: ti-cpufreq: Update efuse/rev offsets in
 AM62 family

On 9/25/24 9:54 AM, Dhruva Gole wrote:
> With the Silicon revision being taken directly from socinfo, there's no
> longer any need for reading any SOC register for revision from this driver.
> Hence, we do not require any rev_offset for AM62 family of devices.
> The efuse offset should be 0x0 for AM625 as well, as the syscon
> register being used from DT refers to the efuse_offset directly.
> 
> However, to maintain the backward compatibility with old devicetree, also
> add condition to handle the case where we have the wrong offset and add
> the older efuse_offset value there such that we don't end up reading the
> wrong register offset.
> 
> Signed-off-by: Dhruva Gole <d-gole@...com>
> ---
>   drivers/cpufreq/ti-cpufreq.c | 23 +++++++++++++++++------
>   1 file changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/cpufreq/ti-cpufreq.c b/drivers/cpufreq/ti-cpufreq.c
> index ba621ce1cdda694c98867422dbb7f10c0df2afef..8a97b95b4c44a76b12cab76ddc0f9a5b8ae73f84 100644
> --- a/drivers/cpufreq/ti-cpufreq.c
> +++ b/drivers/cpufreq/ti-cpufreq.c
> @@ -313,10 +313,9 @@ static const struct soc_device_attribute k3_cpufreq_soc[] = {
>   
>   static struct ti_cpufreq_soc_data am625_soc_data = {
>   	.efuse_xlate = am625_efuse_xlate,
> -	.efuse_offset = 0x0018,
> +	.efuse_offset = 0x0,
>   	.efuse_mask = 0x07c0,
>   	.efuse_shift = 0x6,
> -	.rev_offset = 0x0014,
>   	.multi_regulator = false,
>   };
>   
> @@ -325,7 +324,6 @@ static struct ti_cpufreq_soc_data am62a7_soc_data = {
>   	.efuse_offset = 0x0,
>   	.efuse_mask = 0x07c0,
>   	.efuse_shift = 0x6,
> -	.rev_offset = 0x0014,
>   	.multi_regulator = false,
>   };
>   
> @@ -334,7 +332,6 @@ static struct ti_cpufreq_soc_data am62p5_soc_data = {
>   	.efuse_offset = 0x0,
>   	.efuse_mask = 0x07c0,
>   	.efuse_shift = 0x6,
> -	.rev_offset = 0x0014,
>   	.multi_regulator = false,
>   };
>   
> @@ -349,11 +346,25 @@ static int ti_cpufreq_get_efuse(struct ti_cpufreq_data *opp_data,
>   				u32 *efuse_value)
>   {
>   	struct device *dev = opp_data->cpu_dev;
> +	struct device_node *np = opp_data->opp_node;
>   	u32 efuse;
>   	int ret;
>   
> -	ret = regmap_read(opp_data->syscon, opp_data->soc_data->efuse_offset,
> -			  &efuse);
> +	/*
> +	 * The following check is used as a way to check if this is an older devicetree

"check is used as a way to check" sound redundant, maybe just:

This checks for old AM625 Devicetrees where the syscon was a phandle
to the wkup_conf parent, this required a hard-coded offset to
the efuse register.

> +	 * being used where the entire wkup_conf node was marked as "syscon",
> +	 * "simple-mfd".
> +	 * Since this bug only affects AM625, make sure it enters this condition
> +	 * only for that SoC.
> +	 */
> +	if (of_device_is_compatible(np, "simple-mfd") &&
> +	    of_device_is_compatible(np, "ti,am625")) {

Kinda hacky, but keeping backwards compat often is hacky..

Does `of_device_is_compatible(np, "ti,am625")` actually work here? I'm assuming you
tested with an old DT to make sure this path ever got taken. Maybe put a warning
here that an old DT is in use and the user should update at some point.

Andrew

> +		ret = regmap_read(opp_data->syscon, opp_data->soc_data->efuse_offset + 0x0018,
> +				  &efuse);
> +	} else {
> +		ret = regmap_read(opp_data->syscon, opp_data->soc_data->efuse_offset,
> +				  &efuse);
> +	}
>   	if (opp_data->soc_data->quirks & TI_QUIRK_SYSCON_MAY_BE_MISSING && ret == -EIO) {
>   		/* not a syscon register! */
>   		void __iomem *regs = ioremap(OMAP3_SYSCON_BASE +
>