linux-kernel - Re: [PATCH v7 6/6] cpufreq: ti-cpufreq: Update efuse/rev offsets in AM62 family

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Message-ID: <20240927132711.mfxv4nitr5ygx4tf@throat>
Date: Fri, 27 Sep 2024 08:27:11 -0500
From: Nishanth Menon <nm@...com>
To: Dhruva Gole <d-gole@...com>
CC: 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>,
        <linux-arm-kernel@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
        Andrew Davis
	<afd@...com>, Bryan Brattlof <bb@...com>,
        Vishal Mahaveer <vishalm@...com>, Kevin Hilman <khilman@...libre.com>,
        Markus Schneider-Pargmann
	<msp@...libre.com>
Subject: Re: [PATCH v7 6/6] cpufreq: ti-cpufreq: Update efuse/rev offsets in
 AM62 family

On 14:04-20240926, Dhruva Gole wrote:
[...]

> +	/*
> +	 * 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.
> +	 * This node had the compatibles "syscon", "simple-mfd".
> +	 */
> +	if (of_device_is_compatible(np, "simple-mfd") &&
> +	    of_machine_is_compatible("ti,am625")) {
> +		dev_warn(dev,
> +			 "%s: An old devicetree is in use, please consider updating at some point!",
> +			 __func__);

No need to print.. just handle it seamlessly.

> +		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 +


All these hanky panky is because sycon does not report access fails when
syscon reg size is 1 word.

https://lore.kernel.org/linux-arm-kernel/20240903184710.1552067-1-nm@ti.com/
fixes that. With that applied, instead of using explicit property of the
syscon - which could change simple-mfd or simple-bus or what ever.. Let
us use the quirk for backward compatibility (introduced for similar
messy old code), consider the following (macro probably needs a better
naming):

diff --git a/drivers/cpufreq/ti-cpufreq.c b/drivers/cpufreq/ti-cpufreq.c
index ba621ce1cdda..f0d76fc02ff2 100644
--- a/drivers/cpufreq/ti-cpufreq.c
+++ b/drivers/cpufreq/ti-cpufreq.c
@@ -93,6 +93,8 @@ struct ti_cpufreq_soc_data {
 	bool multi_regulator;
 /* Backward compatibility hack: Might have missing syscon */
 #define TI_QUIRK_SYSCON_MAY_BE_MISSING	0x1
+/* Backward compatibility hack: new syscon size is 1 register wide */
+#define TI_QUIRK_SYSCON_NEW_SINGLE_REG	0x2
 	u8 quirks;
 };
 
@@ -318,6 +320,7 @@ static struct ti_cpufreq_soc_data am625_soc_data = {
 	.efuse_shift = 0x6,
 	.rev_offset = 0x0014,
 	.multi_regulator = false,
+	.quirks = TI_QUIRK_SYSCON_NEW_SINGLE_REG,
 };
 
 static struct ti_cpufreq_soc_data am62a7_soc_data = {
@@ -354,6 +357,10 @@ static int ti_cpufreq_get_efuse(struct ti_cpufreq_data *opp_data,
 
 	ret = regmap_read(opp_data->syscon, opp_data->soc_data->efuse_offset,
 			  &efuse);
+
+	if (opp_data->soc_data->quirks & TI_QUIRK_SYSCON_NEW_SINGLE_REG && ret == -EIO)
+		ret = regmap_read(opp_data->syscon, 0x0, &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 +

-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D