Date:   Mon, 2 Dec 2019 22:09:26 +0100
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Linux-OMAP <linux-omap@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        Adam Ford <aford173@...il.com>,
        André Roth <neolynx@...il.com>,
        Nishanth Menon <nm@...com>, Tero Kristo <t-kristo@...com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>,
        Andreas Kemnade <andreas@...nade.info>
Subject: Re: [PATCH] ARM: OMAP2+: Fix warnings with broken omap2_set_init_voltage()

Hi Tony,

> Am 25.09.2019 um 01:32 schrieb Tony Lindgren <tony@...mide.com>:
> 
> This code is currently unable to find the dts opp tables as ti-cpufreq
> needs to set them up first based on speed binning.
> 
> We stopped initializing the opp tables with platform code years ago for
> device tree based booting with commit 92d51856d740 ("ARM: OMAP3+: do not
> register non-dt OPP tables for device tree boot"), and all of mach-omap2
> is now booting using device tree.
> 
> We currently get the following errors on init:
> 
> omap2_set_init_voltage: unable to find boot up OPP for vdd_mpu
> omap2_set_init_voltage: unable to set vdd_mpu
> omap2_set_init_voltage: unable to find boot up OPP for vdd_core
> omap2_set_init_voltage: unable to set vdd_core
> omap2_set_init_voltage: unable to find boot up OPP for vdd_iva
> omap2_set_init_voltage: unable to set vdd_iva
> 
> Let's just drop the unused code. Nowadays ti-cpufreq should be used to
> to initialize things properly.
> 
> Cc: Adam Ford <aford173@...il.com>
> Cc: André Roth <neolynx@...il.com>
> Cc: "H. Nikolaus Schaller" <hns@...delico.com>
> Cc: Nishanth Menon <nm@...com>
> Cc: Tero Kristo <t-kristo@...com>
> Signed-off-by: Tony Lindgren <tony@...mide.com>
> ---
> 
> Guys, please check and ack if we can really do this to get rid of some
> pointless dmesg -l3 errors without affecting the ongoing cpufreq and
> voltage work.

unfortunately we did not yet test in combination with the 1GHz OPP
patches for omap3630 (queued for v5.5-rc1) and it appears that this
patch breaks the 1GHz OPP.

The symptom is that it works fine on a dm3730 with 800MHz rating
but results in spurious kernel panics, stack corruption, virtual memory
failures, OneNAND DMA timeouts etc. on a dm3730 with 1GHz speed grade.

We can also re-add the "turbo-mode" tags in the omap36xx.dtsi (or
remove the 1GHz OPP) and can then boot with 800MHz max. clock. But
enabling boost (echo 1 >/sys/devices/system/cpu/cpufreq/boost) makes
the problem and its symptoms appear almost immediately.

After some scratching our heads we found that v5.3.7 is still good and
v5.3.8 is bad. A bisect of our tree (which includes the 1GHz OPP) did
point to this patch whichwas apparently already backported to v5.3.8 and
v5.4.

So I assume that the code removed here enabled or initialized something
we need for safe 1GHz transitions. Maybe the ABB-LDO. Or it looks up the
vdd regulator and initializes it earlier than without this code. Maybe
it also (pre-)initializes some clk which could now be left uninitialized
too long?

Note that seeing the log message indicates that voltdm_scale() and
dev_pm_opp_get_voltage() are not called, but all functions before could
be with side-effects.

v5.5-rc1 will likely fail right from the beginning (only on 1GHz rated
omap36xx) because it makes the combination of this patch and 1GHz OPP
public (linux-next should already fail but it appears that nobody has
tested).

Any ideas how to fix? Before I try to do a revert and then add goto exit;
after each function call and see which ones are essential for 1GHz.

BR,
Nikolaus


> 
> ---
> arch/arm/mach-omap2/pm.c | 100 ---------------------------------------
> 1 file changed, 100 deletions(-)
> 
> diff --git a/arch/arm/mach-omap2/pm.c b/arch/arm/mach-omap2/pm.c
> --- a/arch/arm/mach-omap2/pm.c
> +++ b/arch/arm/mach-omap2/pm.c
> @@ -74,83 +74,6 @@ int omap_pm_clkdms_setup(struct clockdomain *clkdm, void *unused)
> 	return 0;
> }
> 
> -/*
> - * This API is to be called during init to set the various voltage
> - * domains to the voltage as per the opp table. Typically we boot up
> - * at the nominal voltage. So this function finds out the rate of
> - * the clock associated with the voltage domain, finds out the correct
> - * opp entry and sets the voltage domain to the voltage specified
> - * in the opp entry
> - */
> -static int __init omap2_set_init_voltage(char *vdd_name, char *clk_name,
> -					 const char *oh_name)
> -{
> -	struct voltagedomain *voltdm;
> -	struct clk *clk;
> -	struct dev_pm_opp *opp;
> -	unsigned long freq, bootup_volt;
> -	struct device *dev;
> -
> -	if (!vdd_name || !clk_name || !oh_name) {
> -		pr_err("%s: invalid parameters\n", __func__);
> -		goto exit;
> -	}
> -
> -	if (!strncmp(oh_name, "mpu", 3))
> -		/* 
> -		 * All current OMAPs share voltage rail and clock
> -		 * source, so CPU0 is used to represent the MPU-SS.
> -		 */
> -		dev = get_cpu_device(0);
> -	else
> -		dev = omap_device_get_by_hwmod_name(oh_name);
> -
> -	if (IS_ERR(dev)) {
> -		pr_err("%s: Unable to get dev pointer for hwmod %s\n",
> -			__func__, oh_name);
> -		goto exit;
> -	}
> -
> -	voltdm = voltdm_lookup(vdd_name);
> -	if (!voltdm) {
> -		pr_err("%s: unable to get vdd pointer for vdd_%s\n",
> -			__func__, vdd_name);
> -		goto exit;
> -	}
> -
> -	clk =  clk_get(NULL, clk_name);
> -	if (IS_ERR(clk)) {
> -		pr_err("%s: unable to get clk %s\n", __func__, clk_name);
> -		goto exit;
> -	}
> -
> -	freq = clk_get_rate(clk);
> -	clk_put(clk);
> -
> -	opp = dev_pm_opp_find_freq_ceil(dev, &freq);
> -	if (IS_ERR(opp)) {
> -		pr_err("%s: unable to find boot up OPP for vdd_%s\n",
> -			__func__, vdd_name);
> -		goto exit;
> -	}
> -
> -	bootup_volt = dev_pm_opp_get_voltage(opp);
> -	dev_pm_opp_put(opp);
> -
> -	if (!bootup_volt) {
> -		pr_err("%s: unable to find voltage corresponding to the bootup OPP for vdd_%s\n",
> -		       __func__, vdd_name);
> -		goto exit;
> -	}
> -
> -	voltdm_scale(voltdm, bootup_volt);
> -	return 0;
> -
> -exit:
> -	pr_err("%s: unable to set vdd_%s\n", __func__, vdd_name);
> -	return -EINVAL;
> -}
> -
> #ifdef CONFIG_SUSPEND
> static int omap_pm_enter(suspend_state_t suspend_state)
> {
> @@ -208,25 +131,6 @@ void omap_common_suspend_init(void *pm_suspend)
> }
> #endif /* CONFIG_SUSPEND */
> 
> -static void __init omap3_init_voltages(void)
> -{
> -	if (!soc_is_omap34xx())
> -		return;
> -
> -	omap2_set_init_voltage("mpu_iva", "dpll1_ck", "mpu");
> -	omap2_set_init_voltage("core", "l3_ick", "l3_main");
> -}
> -
> -static void __init omap4_init_voltages(void)
> -{
> -	if (!soc_is_omap44xx())
> -		return;
> -
> -	omap2_set_init_voltage("mpu", "dpll_mpu_ck", "mpu");
> -	omap2_set_init_voltage("core", "l3_div_ck", "l3_main_1");
> -	omap2_set_init_voltage("iva", "dpll_iva_m5x2_ck", "iva");
> -}
> -
> int __maybe_unused omap_pm_nop_init(void)
> {
> 	return 0;
> @@ -246,10 +150,6 @@ int __init omap2_common_pm_late_init(void)
> 	omap4_twl_init();
> 	omap_voltage_late_init();
> 
> -	/* Initialize the voltages */
> -	omap3_init_voltages();
> -	omap4_init_voltages();
> -
> 	/* Smartreflex device init */
> 	omap_devinit_smartreflex();
> 
> -- 
> 2.23.0

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