Re: [PATCH v8 14/21] clk: tegra210: Add suspend and resume support

[Dmitry Osipenko]

11.08.2019 22:15, Sowjanya Komatineni ÐÐÑÐÑ:
> 
> On 8/11/19 10:39 AM, Dmitry Osipenko wrote:
>> 09.08.2019 21:40, Sowjanya Komatineni ÐÐÑÐÑ:
>>> On 8/9/19 11:18 AM, Dmitry Osipenko wrote:
>>>> 09.08.2019 19:19, Sowjanya Komatineni ÐÐÑÐÑ:
>>>>> On 8/9/19 6:56 AM, Dmitry Osipenko wrote:
>>>>>> 09.08.2019 2:46, Sowjanya Komatineni ÐÐÑÐÑ:
>>>>>>> This patch adds support for clk: tegra210: suspend-resume.
>>>>>>>
>>>>>>> All the CAR controller settings are lost on suspend when core
>>>>>>> power goes off.
>>>>>>>
>>>>>>> This patch has implementation for saving and restoring all PLLs
>>>>>>> and clocks context during system suspend and resume to have the
>>>>>>> clocks back to same state for normal operation.
>>>>>>>
>>>>>>> Clock driver suspend and resume are registered as syscore_ops as clocks
>>>>>>> restore need to happen before the other drivers resume to have all their
>>>>>>> clocks back to the same state as before suspend.
>>>>>>>
>>>>>>> Signed-off-by: Sowjanya Komatineni <skomatineni@xxxxxxxxxx>
>>>>>>> ---
>>>>>>> ÂÂ drivers/clk/tegra/clk-tegra210.c | 103 +++++++++++++++++++++++++++++++++++++--
>>>>>>> ÂÂ drivers/clk/tegra/clk.cÂÂÂÂÂÂÂÂÂ |Â 64 ++++++++++++++++++++++++
>>>>>>> ÂÂ drivers/clk/tegra/clk.hÂÂÂÂÂÂÂÂÂ |ÂÂ 3 ++
>>>>>>> ÂÂ 3 files changed, 166 insertions(+), 4 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/clk/tegra/clk-tegra210.c b/drivers/clk/tegra/clk-tegra210.c
>>>>>>> index 998bf60b219a..8dd6f4f4debb 100644
>>>>>>> --- a/drivers/clk/tegra/clk-tegra210.c
>>>>>>> +++ b/drivers/clk/tegra/clk-tegra210.c
>>>>>>> @@ -9,13 +9,13 @@
>>>>>>> ÂÂ #include <linux/clkdev.h>
>>>>>>> ÂÂ #include <linux/of.h>
>>>>>>> ÂÂ #include <linux/of_address.h>
>>>>>>> +#include <linux/syscore_ops.h>
>>>>>>> ÂÂ #include <linux/delay.h>
>>>>>>> ÂÂ #include <linux/export.h>
>>>>>>> ÂÂ #include <linux/mutex.h>
>>>>>>> ÂÂ #include <linux/clk/tegra.h>
>>>>>>> ÂÂ #include <dt-bindings/clock/tegra210-car.h>
>>>>>>> ÂÂ #include <dt-bindings/reset/tegra210-car.h>
>>>>>>> -#include <linux/iopoll.h>
>>>>>>> ÂÂ #include <linux/sizes.h>
>>>>>>> ÂÂ #include <soc/tegra/pmc.h>
>>>>>>> ÂÂ @@ -220,11 +220,15 @@
>>>>>>> ÂÂ #define CLK_M_DIVISOR_SHIFT 2
>>>>>>> ÂÂ #define CLK_M_DIVISOR_MASK 0x3
>>>>>>> ÂÂ +#define CLK_MASK_ARMÂÂÂ 0x44
>>>>>>> +#define MISC_CLK_ENBÂÂÂ 0x48
>>>>>>> +
>>>>>>> ÂÂ #define RST_DFLL_DVCO 0x2f4
>>>>>>> ÂÂ #define DVFS_DFLL_RESET_SHIFT 0
>>>>>>> ÂÂ Â #define CLK_RST_CONTROLLER_RST_DEV_Y_SET 0x2a8
>>>>>>> ÂÂ #define CLK_RST_CONTROLLER_RST_DEV_Y_CLR 0x2ac
>>>>>>> +#define CPU_SOFTRST_CTRL 0x380
>>>>>>> ÂÂ Â #define LVL2_CLK_GATE_OVRA 0xf8
>>>>>>> ÂÂ #define LVL2_CLK_GATE_OVRC 0x3a0
>>>>>>> @@ -2825,6 +2829,7 @@ static int tegra210_enable_pllu(void)
>>>>>>> ÂÂÂÂÂÂ struct tegra_clk_pll_freq_table *fentry;
>>>>>>> ÂÂÂÂÂÂ struct tegra_clk_pll pllu;
>>>>>>> ÂÂÂÂÂÂ u32 reg;
>>>>>>> +ÂÂÂ int ret;
>>>>>>> ÂÂ ÂÂÂÂÂ for (fentry = pll_u_freq_table; fentry->input_rate; fentry++) {
>>>>>>> ÂÂÂÂÂÂÂÂÂÂ if (fentry->input_rate == pll_ref_freq)
>>>>>>> @@ -2853,9 +2858,14 @@ static int tegra210_enable_pllu(void)
>>>>>>> ÂÂÂÂÂÂ reg |= PLL_ENABLE;
>>>>>>> ÂÂÂÂÂÂ writel(reg, clk_base + PLLU_BASE);
>>>>>>> ÂÂ -ÂÂÂ readl_relaxed_poll_timeout_atomic(clk_base + PLLU_BASE, reg,
>>>>>>> -ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ reg & PLL_BASE_LOCK, 2, 1000);
>>>>>>> -ÂÂÂ if (!(reg & PLL_BASE_LOCK)) {
>>>>>>> +ÂÂÂ /*
>>>>>>> +ÂÂÂÂ * During clocks resume, same PLLU init and enable sequence get
>>>>>>> +ÂÂÂÂ * executed. So, readx_poll_timeout_atomic can't be used here as it
>>>>>>> +ÂÂÂÂ * uses ktime_get() and timekeeping resume doesn't happen by that
>>>>>>> +ÂÂÂÂ * time. So, using tegra210_wait_for_mask for PLL LOCK.
>>>>>>> +ÂÂÂÂ */
>>>>>>> +ÂÂÂ ret = tegra210_wait_for_mask(&pllu, PLLU_BASE, PLL_BASE_LOCK);
>>>>>>> +ÂÂÂ if (ret) {
>>>>>>> ÂÂÂÂÂÂÂÂÂÂ pr_err("Timed out waiting for PLL_U to lock\n");
>>>>>>> ÂÂÂÂÂÂÂÂÂÂ return -ETIMEDOUT;
>>>>>>> ÂÂÂÂÂÂ }
>>>>>>> @@ -3288,6 +3298,84 @@ static void tegra210_disable_cpu_clock(u32 cpu)
>>>>>>> ÂÂ }
>>>>>>> ÂÂ Â #ifdef CONFIG_PM_SLEEP
>>>>>>> +/*
>>>>>>> + * This array lists mask values for each peripheral clk bank
>>>>>>> + * to mask out reserved bits during the clocks state restore
>>>>>>> + * on SC7 resume to prevent accidental writes to these reserved
>>>>>>> + * bits.
>>>>>>> + */
>>>>>>> +static u32 periph_clk_rsvd_mask[TEGRA210_CAR_BANK_COUNT] = {
>>>>>> Should be more natural to have a "valid_mask" instead of "rsvd_mask".
>>>>>>
>>>>>> What's actually wrong with touching of the reserved bits? They must be NO-OP.. or the
>>>>>> reserved bits are actually some kind of "secret" bits? If those bits have some use-case
>>>>>> outside of Silicon HW (like FPGA simulation), then this doesn't matter for upstream
>>>>>> and you
>>>>>> have to keep the workaround locally in the downstream kernel or whatever.
>>>>> Will rename as valid_mask.
>>>>>
>>>>> some bits in these registers are undefined and is not good to write to these bits as they
>>>>> can cause pslverr.
>>>> Okay, it should be explained in the comment.
>>>>
>>>> Is it possible to disable trapping of changing the undefined bits?
>>> No its internal to design
>> Okay.
>>
>> Also, what about to move the valid_mask into struct tegra_clk_periph_regs?
> 
> No, we cannot move to tegra_clk_periph_regs as its in tegra/clk.c and is common for all tegra.
> 
> Reserved bits are different on tegra chips so should come from Tegra chip specific clock
> driver like
> 
> clk-tegra210 for Tegra210.

Could you please check whether the reserved bits are RAZ (read as zero)?

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