Message-ID: <348e9382-9978-0c01-1493-4226c1cd70a3@nvidia.com>
Date:   Mon, 2 Dec 2019 16:07:53 -0800
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <mperttunen@...dia.com>,
        <gregkh@...uxfoundation.org>, <sboyd@...nel.org>,
        <tglx@...utronix.de>, <robh+dt@...nel.org>, <mark.rutland@....com>
CC:     <allison@...utok.net>, <pdeschrijver@...dia.com>,
        <pgaikwad@...dia.com>, <mturquette@...libre.com>,
        <horms+renesas@...ge.net.au>, <Jisheng.Zhang@...aptics.com>,
        <krzk@...nel.org>, <arnd@...db.de>, <spujar@...dia.com>,
        <josephl@...dia.com>, <vidyas@...dia.com>,
        <daniel.lezcano@...aro.org>, <mmaddireddy@...dia.com>,
        <markz@...dia.com>, <devicetree@...r.kernel.org>,
        <linux-clk@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 02/11] soc: tegra: Add Tegra PMC clock registrations
 into PMC driver


On 12/2/19 3:14 PM, Sowjanya Komatineni wrote:
>
> On 12/2/19 3:10 PM, Sowjanya Komatineni wrote:
>>
>> On 12/2/19 2:58 PM, Sowjanya Komatineni wrote:
>>>
>>> On 12/2/19 1:50 PM, Dmitry Osipenko wrote:
>>>> 02.12.2019 23:09, Sowjanya Komatineni пишет:
>>>>> On 11/28/19 5:25 AM, Dmitry Osipenko wrote:
>>>>>> 28.11.2019 01:57, Sowjanya Komatineni пишет:
>>>>>>> On 11/27/19 7:14 AM, Dmitry Osipenko wrote:
>>>>>>>> 27.11.2019 07:59, Sowjanya Komatineni пишет:
>>>>>>>>> Tegra210 and prior Tegra PMC has clk_out_1, clk_out_2, 
>>>>>>>>> clk_out_3 with
>>>>>>>>> mux and gate for each of these clocks.
>>>>>>>>>
>>>>>>>>> Currently these PMC clocks are registered by Tegra clock 
>>>>>>>>> driver using
>>>>>>>>> clk_register_mux and clk_register_gate by passing PMC base 
>>>>>>>>> address
>>>>>>>>> and register offsets and PMC programming for these clocks happens
>>>>>>>>> through direct PMC access by the clock driver.
>>>>>>>>>
>>>>>>>>> With this, when PMC is in secure mode any direct PMC access 
>>>>>>>>> from the
>>>>>>>>> non-secure world does not go through and these clocks will not be
>>>>>>>>> functional.
>>>>>>>>>
>>>>>>>>> This patch adds these clocks registration with PMC as a clock 
>>>>>>>>> provider
>>>>>>>>> for these clocks. clk_ops callback implementations for these 
>>>>>>>>> clocks
>>>>>>>>> uses tegra_pmc_readl and tegra_pmc_writel which supports PMC
>>>>>>>>> programming
>>>>>>>>> in secure mode and non-secure mode.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
>>>>>>>>> ---
>>>>>>>>>     drivers/soc/tegra/pmc.c | 330
>>>>>>>>> ++++++++++++++++++++++++++++++++++++++++++++++++
>>>>>>>>>     1 file changed, 330 insertions(+)
>>>>>>>>>
>>>>>>>>> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
>>>>>>>>> index ea0e11a09c12..a353f6d0a832 100644
>>>>>>>>> --- a/drivers/soc/tegra/pmc.c
>>>>>>>>> +++ b/drivers/soc/tegra/pmc.c
>>>>>>>>> @@ -13,6 +13,9 @@
>>>>>>>>>       #include <linux/arm-smccc.h>
>>>>>>>>>     #include <linux/clk.h>
>>>>>>>>> +#include <linux/clk-provider.h>
>>>>>>>>> +#include <linux/clkdev.h>
>>>>>>>>> +#include <linux/clk/clk-conf.h>
>>>>>>>>>     #include <linux/clk/tegra.h>
>>>>>>>>>     #include <linux/debugfs.h>
>>>>>>>>>     #include <linux/delay.h>
>>>>>>>>> @@ -48,6 +51,7 @@
>>>>>>>>>     #include <dt-bindings/pinctrl/pinctrl-tegra-io-pad.h>
>>>>>>>>>     #include <dt-bindings/gpio/tegra186-gpio.h>
>>>>>>>>>     #include <dt-bindings/gpio/tegra194-gpio.h>
>>>>>>>>> +#include <dt-bindings/soc/tegra-pmc.h>
>>>>>>>>>       #define PMC_CNTRL            0x0
>>>>>>>>>     #define  PMC_CNTRL_INTR_POLARITY    BIT(17) /* inverts INTR
>>>>>>>>> polarity */
>>>>>>>>> @@ -100,6 +104,7 @@
>>>>>>>>>     #define PMC_WAKE2_STATUS        0x168
>>>>>>>>>     #define PMC_SW_WAKE2_STATUS        0x16c
>>>>>>>>>     +#define PMC_CLK_OUT_CNTRL        0x1a8
>>>>>>>>>     #define PMC_SENSOR_CTRL            0x1b0
>>>>>>>>>     #define  PMC_SENSOR_CTRL_SCRATCH_WRITE BIT(2)
>>>>>>>>>     #define  PMC_SENSOR_CTRL_ENABLE_RST    BIT(1)
>>>>>>>>> @@ -155,6 +160,91 @@
>>>>>>>>>     #define  TEGRA_SMC_PMC_READ    0xaa
>>>>>>>>>     #define  TEGRA_SMC_PMC_WRITE    0xbb
>>>>>>>>>     +struct pmc_clk_mux {
>>>>>>>>> +    struct clk_hw    hw;
>>>>>>>>> +    unsigned long    offs;
>>>>>>>>> +    u32        mask;
>>>>>>>>> +    u32        shift;
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +#define to_pmc_clk_mux(_hw) container_of(_hw, struct 
>>>>>>>>> pmc_clk_mux, hw)
>>>>>>>>> +
>>>>>>>>> +struct pmc_clk_gate {
>>>>>>>>> +    struct clk_hw    hw;
>>>>>>>>> +    unsigned long    offs;
>>>>>>>>> +    u32        shift;
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +#define to_pmc_clk_gate(_hw) container_of(_hw, struct
>>>>>>>>> pmc_clk_gate, hw)
>>>>>>>>> +
>>>>>>>>> +struct pmc_clk_init_data {
>>>>>>>>> +    char *mux_name;
>>>>>>>>> +    char *gate_name;
>>>>>>>>> +    const char **parents;
>>>>>>>>> +    int num_parents;
>>>>>>>>> +    int mux_id;
>>>>>>>>> +    int gate_id;
>>>>>>>>> +    char *dev_name;
>>>>>>>>> +    u8 mux_shift;
>>>>>>>>> +    u8 gate_shift;
>>>>>>>>> +    u8 init_parent_index;
>>>>>>>>> +    int init_state;
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +static const char *clk_out1_parents[] = { "clk_m", "clk_m_div2",
>>>>>>>>> +    "clk_m_div4", "extern1",
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +static const char *clk_out2_parents[] = { "clk_m", "clk_m_div2",
>>>>>>>>> +    "clk_m_div4", "extern2",
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +static const char *clk_out3_parents[] = { "clk_m", "clk_m_div2",
>>>>>>>>> +    "clk_m_div4", "extern3",
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +static struct pmc_clk_init_data tegra_pmc_clks_data[] = {
>>>>>>>>> +    {
>>>>>>>>> +        .mux_name = "clk_out_1_mux",
>>>>>>>>> +        .gate_name = "clk_out_1",
>>>>>>>>> +        .parents = clk_out1_parents,
>>>>>>>>> +        .num_parents = ARRAY_SIZE(clk_out1_parents),
>>>>>>>>> +        .mux_id = TEGRA_PMC_CLK_OUT_1_MUX,
>>>>>>>>> +        .gate_id = TEGRA_PMC_CLK_OUT_1,
>>>>>>>>> +        .dev_name = "extern1",
>>>>>>>>> +        .mux_shift = 6,
>>>>>>>>> +        .gate_shift = 2,
>>>>>>>>> +        .init_parent_index = 3,
>>>>>>>>> +        .init_state = 1,
>>>>>>>>> +    },
>>>>>>>>> +    {
>>>>>>>>> +        .mux_name = "clk_out_2_mux",
>>>>>>>>> +        .gate_name = "clk_out_2",
>>>>>>>>> +        .parents = clk_out2_parents,
>>>>>>>>> +        .num_parents = ARRAY_SIZE(clk_out2_parents),
>>>>>>>>> +        .mux_id = TEGRA_PMC_CLK_OUT_2_MUX,
>>>>>>>>> +        .gate_id = TEGRA_PMC_CLK_OUT_2,
>>>>>>>>> +        .dev_name = "extern2",
>>>>>>>>> +        .mux_shift = 14,
>>>>>>>>> +        .gate_shift = 10,
>>>>>>>>> +        .init_parent_index = 0,
>>>>>>>>> +        .init_state = 0,
>>>>>>>>> +    },
>>>>>>>>> +    {
>>>>>>>>> +        .mux_name = "clk_out_3_mux",
>>>>>>>>> +        .gate_name = "clk_out_3",
>>>>>>>>> +        .parents = clk_out3_parents,
>>>>>>>>> +        .num_parents = ARRAY_SIZE(clk_out3_parents),
>>>>>>>>> +        .mux_id = TEGRA_PMC_CLK_OUT_3_MUX,
>>>>>>>>> +        .gate_id = TEGRA_PMC_CLK_OUT_3,
>>>>>>>>> +        .dev_name = "extern3",
>>>>>>>>> +        .mux_shift = 22,
>>>>>>>>> +        .gate_shift = 18,
>>>>>>>>> +        .init_parent_index = 0,
>>>>>>>>> +        .init_state = 0,
>>>>>>>>> +    },
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>>     struct tegra_powergate {
>>>>>>>>>         struct generic_pm_domain genpd;
>>>>>>>>>         struct tegra_pmc *pmc;
>>>>>>>>> @@ -254,6 +344,9 @@ struct tegra_pmc_soc {
>>>>>>>>>          */
>>>>>>>>>         const struct tegra_wake_event *wake_events;
>>>>>>>>>         unsigned int num_wake_events;
>>>>>>>>> +
>>>>>>>>> +    struct pmc_clk_init_data *pmc_clks_data;
>>>>>>>>> +    unsigned int num_pmc_clks;
>>>>>>>>>     };
>>>>>>>>>       static const char * const tegra186_reset_sources[] = {
>>>>>>>>> @@ -2163,6 +2256,228 @@ static int tegra_pmc_clk_notify_cb(struct
>>>>>>>>> notifier_block *nb,
>>>>>>>>>         return NOTIFY_OK;
>>>>>>>>>     }
>>>>>>>>>     +static void pmc_clk_fence_udelay(u32 offset)
>>>>>>>>> +{
>>>>>>>>> +    tegra_pmc_readl(pmc, offset);
>>>>>>>>> +    /* pmc clk propagation delay 2 us */
>>>>>>>>> +    udelay(2);
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static u8 pmc_clk_mux_get_parent(struct clk_hw *hw)
>>>>>>>>> +{
>>>>>>>>> +    struct pmc_clk_mux *mux = to_pmc_clk_mux(hw);
>>>>>>>>> +    int num_parents = clk_hw_get_num_parents(hw);
>>>>>>>>> +    u32 val;
>>>>>>>>> +
>>>>>>>>> +    val = tegra_pmc_readl(pmc, mux->offs) >> mux->shift;
>>>>>>>>> +    val &= mux->mask;
>>>>>>>>> +
>>>>>>>>> +    if (val >= num_parents)
>>>>>>>>> +        return -EINVAL;
>>>>>>>>> +
>>>>>>>>> +    return val;
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static int pmc_clk_mux_set_parent(struct clk_hw *hw, u8 index)
>>>>>>>>> +{
>>>>>>>>> +    struct pmc_clk_mux *mux = to_pmc_clk_mux(hw);
>>>>>>>>> +    u32 val;
>>>>>>>>> +
>>>>>>>>> +    val = tegra_pmc_readl(pmc, mux->offs);
>>>>>>>>> +    val &= ~(mux->mask << mux->shift);
>>>>>>>>> +    val |= index << mux->shift;
>>>>>>>>> +    tegra_pmc_writel(pmc, val, mux->offs);
>>>>>>>>> +    pmc_clk_fence_udelay(mux->offs);
>>>>>>>>> +
>>>>>>>>> +    return 0;
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static const struct clk_ops pmc_clk_mux_ops = {
>>>>>>>>> +    .get_parent = pmc_clk_mux_get_parent,
>>>>>>>>> +    .set_parent = pmc_clk_mux_set_parent,
>>>>>>>>> +    .determine_rate = __clk_mux_determine_rate,
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +static struct clk *
>>>>>>>>> +tegra_pmc_clk_mux_register(const char *name, const char * const
>>>>>>>>> *parent_names,
>>>>>>>>> +               int num_parents, unsigned long flags,
>>>>>>>>> +               unsigned long offset, u32 shift, u32 mask)
>>>>>>>>> +{
>>>>>>>>> +    struct clk_init_data init;
>>>>>>>>> +    struct pmc_clk_mux *mux;
>>>>>>>>> +
>>>>>>>>> +    mux = kzalloc(sizeof(*mux), GFP_KERNEL);
>>>>>>>>> +    if (!mux)
>>>>>>>>> +        return ERR_PTR(-ENOMEM);
>>>>>>>>> +
>>>>>>>>> +    init.name = name;
>>>>>>>>> +    init.ops = &pmc_clk_mux_ops;
>>>>>>>>> +    init.parent_names = parent_names;
>>>>>>>>> +    init.num_parents = num_parents;
>>>>>>>>> +    init.flags = flags;
>>>>>>>>> +
>>>>>>>>> +    mux->hw.init = &init;
>>>>>>>>> +    mux->offs = offset;
>>>>>>>>> +    mux->mask = mask;
>>>>>>>>> +    mux->shift = shift;
>>>>>>>>> +
>>>>>>>>> +    return clk_register(NULL, &mux->hw);
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static int pmc_clk_is_enabled(struct clk_hw *hw)
>>>>>>>>> +{
>>>>>>>>> +    struct pmc_clk_gate *gate = to_pmc_clk_gate(hw);
>>>>>>>>> +
>>>>>>>>> +    return tegra_pmc_readl(pmc, gate->offs) & 
>>>>>>>>> BIT(gate->shift) ? 1
>>>>>>>>> : 0;
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static void pmc_clk_set_state(struct clk_hw *hw, int state)
>>>>>>>>> +{
>>>>>>>>> +    struct pmc_clk_gate *gate = to_pmc_clk_gate(hw);
>>>>>>>>> +    u32 val;
>>>>>>>>> +
>>>>>>>>> +    val = tegra_pmc_readl(pmc, gate->offs);
>>>>>>>>> +    val = state ? (val | BIT(gate->shift)) : (val &
>>>>>>>>> ~BIT(gate->shift));
>>>>>>>>> +    tegra_pmc_writel(pmc, val, gate->offs);
>>>>>>>>> +    pmc_clk_fence_udelay(gate->offs);
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static int pmc_clk_enable(struct clk_hw *hw)
>>>>>>>>> +{
>>>>>>>>> +    pmc_clk_set_state(hw, 1);
>>>>>>>>> +
>>>>>>>>> +    return 0;
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static void pmc_clk_disable(struct clk_hw *hw)
>>>>>>>>> +{
>>>>>>>>> +    pmc_clk_set_state(hw, 0);
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static const struct clk_ops pmc_clk_gate_ops = {
>>>>>>>>> +    .is_enabled = pmc_clk_is_enabled,
>>>>>>>>> +    .enable = pmc_clk_enable,
>>>>>>>>> +    .disable = pmc_clk_disable,
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +static struct clk *
>>>>>>>>> +tegra_pmc_clk_gate_register(const char *name, const char
>>>>>>>>> *parent_name,
>>>>>>>>> +                unsigned long flags, unsigned long offset,
>>>>>>>>> +                u32 shift)
>>>>>>>>> +{
>>>>>>>>> +    struct clk_init_data init;
>>>>>>>>> +    struct pmc_clk_gate *gate;
>>>>>>>>> +
>>>>>>>>> +    gate = kzalloc(sizeof(*gate), GFP_KERNEL);
>>>>>>>>> +    if (!gate)
>>>>>>>>> +        return ERR_PTR(-ENOMEM);
>>>>>>>>> +
>>>>>>>>> +    init.name = name;
>>>>>>>>> +    init.ops = &pmc_clk_gate_ops;
>>>>>>>>> +    init.parent_names = &parent_name;
>>>>>>>>> +    init.num_parents = 1;
>>>>>>>>> +    init.flags = flags;
>>>>>>>>> +
>>>>>>>>> +    gate->hw.init = &init;
>>>>>>>>> +    gate->offs = offset;
>>>>>>>>> +    gate->shift = shift;
>>>>>>>>> +
>>>>>>>>> +    return clk_register(NULL, &gate->hw);
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static void tegra_pmc_clock_register(struct tegra_pmc *pmc,
>>>>>>>>> +                     struct device_node *np)
>>>>>>>>> +{
>>>>>>>>> +    struct clk *clkmux, *clk, *parent;
>>>>>>>>> +    struct clk_onecell_data *clk_data;
>>>>>>>>> +    unsigned int num_clks;
>>>>>>>>> +    int i, ret;
>>>>>>>>> +
>>>>>>>>> +    /* each pmc clock output has a mux and a gate */
>>>>>>>>> +    num_clks = pmc->soc->num_pmc_clks * 2;
>>>>>>>>> +
>>>>>>>>> +    if (!num_clks)
>>>>>>>>> +        return;
>>>>>>>>> +
>>>>>>>>> +    clk_data = kmalloc(sizeof(*clk_data), GFP_KERNEL);
>>>>>>>>> +    if (!clk_data)
>>>>>>>>> +        return;
>>>>>>>>> +
>>>>>>>>> +    clk_data->clks = kcalloc(TEGRA_PMC_CLK_MAX,
>>>>>>>>> sizeof(*clk_data->clks),
>>>>>>>>> +                 GFP_KERNEL);
>>>>>>>>> +    if (!clk_data->clks)
>>>>>>>>> +        goto free_clkdata;
>>>>>>>>> +
>>>>>>>>> +    clk_data->clk_num = num_clks;
>>>>>>>>> +
>>>>>>>>> +    for (i = 0; i < pmc->soc->num_pmc_clks; i++) {
>>>>>>>>> +        struct pmc_clk_init_data *data;
>>>>>>>>> +
>>>>>>>>> +        data = pmc->soc->pmc_clks_data + i;
>>>>>>>>> +
>>>>>>>>> +        clkmux = tegra_pmc_clk_mux_register(data->mux_name,
>>>>>>>>> +                            data->parents,
>>>>>>>>> +                            data->num_parents,
>>>>>>>>> + CLK_SET_RATE_NO_REPARENT |
>>>>>>>>> +                            CLK_SET_RATE_PARENT,
>>>>>>>>> +                            PMC_CLK_OUT_CNTRL,
>>>>>>>>> +                            data->mux_shift, 3);
>>>>>>>>> +        if (IS_ERR(clkmux))
>>>>>>>>> +            goto free_clks;
>>>>>>>>> +
>>>>>>>>> +        clk_data->clks[data->mux_id] = clkmux;
>>>>>>>>> +
>>>>>>>>> +        clk = tegra_pmc_clk_gate_register(data->gate_name,
>>>>>>>>> +                          data->mux_name,
>>>>>>>>> +                          CLK_SET_RATE_PARENT,
>>>>>>>>> +                          PMC_CLK_OUT_CNTRL,
>>>>>>>>> +                          data->gate_shift);
>>>>>>>>> +        if (IS_ERR(clk))
>>>>>>>>> +            goto free_clks;
>>>>>>>>> +
>>>>>>>>> +        clk_data->clks[data->gate_id] = clk;
>>>>>>>>> +
>>>>>>>>> +        ret = clk_set_parent(clk, clkmux);
>>>>>>>>> +        if (ret < 0) {
>>>>>>>>> +            pr_err("failed to set parent of %s to %s\n",
>>>>>>>>> +                   __func__, __clk_get_name(clk),
>>>>>>>>> +                   __clk_get_name(clkmux));
>>>>>>>>> +        }
>>>>>>>>> +
>>>>>>>>> +        clk_register_clkdev(clk, data->dev_name, 
>>>>>>>>> data->gate_name);
>>>>>>>>> +
>>>>>>>>> +        /* configure initial clock parent and state */
>>>>>>>>> +        parent = clk_get_sys(data->gate_name,
>>>>>>>>> + data->parents[data->init_parent_index]);
>>>> Couldn't the default parent be defined using "assigned clock" in a
>>>> device-tree? Please see "Assigned clock parents and rates" in the doc.
>>>>
>>>> https://www.kernel.org/doc/Documentation/devicetree/bindings/clock/clock-bindings.txt 
>>>>
>>>>
>>>> Then you could simply use of_clk_set_defaults(pmc->dev->of_node, 
>>>> true).
>>>
>>> Yes, of_clk_add_provider() does of_clk_set_defaults which sets based 
>>> on assigned parents and clock rates.
>>>
>>> This need device tree to specify assigned clock parent properties. 
>>> Will update device tree and remove init parent from the driver.
>>>
>> assigned-clock properties should be set in consumer node of these 
>> clocks and currently these clocks are not used yet.
>>
>> So will just remove init parent from driver and when these clocks are 
>> used device tree can be updated in corresponding consumer node with 
>> these properties.
>>
> How about default ON/OFF init state for the clocks? I see 
> assigned-clock properties for parent and rate only.
>
> But based on existing clock-tegra-pmc driver, I see clk_out_1 is 
> default enabled with extern1 parent for T30 thru T210 platforms.
>
> Peter/Thierry, What was the reason we enable clk_out_1 right from the 
> clock registration?
>
clk_out_1 is for audio and its not required to be enabled during the 
boot and audio driver can enable/disable it.

same with blink 32khz which is used for WIFI. WIFI driver can 
enable/disable during power up/down sequence and technically as per 
design we dont need to have it always on right from the boot.

So can remove out clocks init states from driver once thierry also agree 
on this.

>>>>
>>>>>>>>> +        if (!IS_ERR(parent)) {
>>>>>>>>> +            ret = clk_set_parent(clkmux, parent);
>>>>>>>>> +            if (ret < 0) {
>>>>>>>>> +                pr_err("failed to set parent of %s to %s\n",
>>>>>>>>> +                       __func__, __clk_get_name(clkmux),
>>>>>>>>> +                       __clk_get_name(parent));
>>>>>>>>> +                WARN_ON(1);
>>>>>>>>> +            }
>>>>>>>>> +        }
>>>>>>>>> +
>>>>>>>>> +        if (data->init_state) {
>>>>>>>>> +            if (clk_prepare_enable(clk)) {
>>>>>>>>> +                pr_err("failed to enable %s\n", __func__,
>>>>>>>>> +                       __clk_get_name(clk));
>>>>>>>>> +                WARN_ON(1);
>>>>>> Alternatively you could write it like this:
>>>>>>
>>>>>>      err = clk_prepare_enable(clk);
>>>>>>
>>>>>>      WARN_ON(err, "failed to enable %s: %d\n",
>>>>>>          __clk_get_name(clk), err);
>>>>>>
>>>>>>>> Should be a bit better to move the WARN_ON to the end of errors
>>>>>>>> handling
>>>>>>>> in order to catch all possible errors:
>>>>>>>>
>>>>>>>> @@ -2510,6 +2510,7 @@ static void tegra_pmc_clock_register(struct
>>>>>>>> tegra_pmc *pmc,
>>>>>>>>            return;
>>>>>>>>
>>>>>>>>     free_clks:
>>>>>>>> +       WARN_ON(1);
>>>>>>>>            kfree(clk_data->clks);
>>>>>>>>     free_clkdata:
>>>>>>>>            kfree(clk_data);
>>>>>>> Reason I had WARN_ON right during clk_set_parent failure is to 
>>>>>>> have the
>>>>>>> loop continue for subsequence pmc clocks registration instead of
>>>>>>> terminating all pmc clocks registration.
>>>>>> Ah, okay. Nevertheless this WARN_ON in the end shouldn't be the 
>>>>>> least
>>>>>> (IMO).
>>>>> Hi Dmitry, Just want to be clear on the above comment. Are you
>>>>> suggesting to add additional WARN_ON at the end?
>>>> Yes, it was my suggestion.
>>>>
>>>>> Thought WARN_ON right during corresponding clock failure with warn
>>>>> message showing clock names will be clear and also other clocks still
>>>>> should be registered.
>>>>>
>>>>> To add additional WARN_ON at the end need to track status of each 
>>>>> clock
>>>>> and use that to as warn condition.
>>>> You could add a warning/error message to every point of failure.
>>>>
>>>> Primarily, it is important not to miss a error. Secondarily, it is
>>>> important to make diagnostic message meaningful.
>>>>
>>>> Realistically, I doubt that this chunk of code will ever fail once 
>>>> it is
>>>> known to work well. So it will be nice to have a more detailed
>>>> diagnostics (just in a case), but it shouldn't be a must.
>>>
>>> OK, Will add additional WARN message "failed registering PMC clocks" 
>>> at the end.
>>>

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