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Fri, 09 Aug 2019 11:18:17 -0700 (PDT) Subject: Re: [PATCH v8 14/21] clk: tegra210: Add suspend and resume support To: Sowjanya Komatineni , thierry.reding@gmail.com, jonathanh@nvidia.com, tglx@linutronix.de, jason@lakedaemon.net, marc.zyngier@arm.com, linus.walleij@linaro.org, stefan@agner.ch, mark.rutland@arm.com Cc: pdeschrijver@nvidia.com, pgaikwad@nvidia.com, sboyd@kernel.org, linux-clk@vger.kernel.org, linux-gpio@vger.kernel.org, jckuo@nvidia.com, josephl@nvidia.com, talho@nvidia.com, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, mperttunen@nvidia.com, spatra@nvidia.com, robh+dt@kernel.org, devicetree@vger.kernel.org, rjw@rjwysocki.net, viresh.kumar@linaro.org, linux-pm@vger.kernel.org References: <1565308020-31952-1-git-send-email-skomatineni@nvidia.com> <1565308020-31952-15-git-send-email-skomatineni@nvidia.com> <7d101ec9-c559-8b40-1764-6bf67a9c7a7a@nvidia.com> From: Dmitry Osipenko Message-ID: Date: Fri, 9 Aug 2019 21:18:15 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <7d101ec9-c559-8b40-1764-6bf67a9c7a7a@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org 09.08.2019 19:19, Sowjanya Komatineni пишет: > > On 8/9/19 6:56 AM, Dmitry Osipenko wrote: >> 09.08.2019 2:46, Sowjanya Komatineni пишет: >>> 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 >>> --- >>>   drivers/clk/tegra/clk-tegra210.c | 103 +++++++++++++++++++++++++++++++++++++-- >>>   drivers/clk/tegra/clk.c          |  64 ++++++++++++++++++++++++ >>>   drivers/clk/tegra/clk.h          |   3 ++ >>>   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 @@ >>>   #include >>>   #include >>>   #include >>> +#include >>>   #include >>>   #include >>>   #include >>>   #include >>>   #include >>>   #include >>> -#include >>>   #include >>>   #include >>>   @@ -220,11 +220,15 @@ >>>   #define CLK_M_DIVISOR_SHIFT 2 >>>   #define CLK_M_DIVISOR_MASK 0x3 >>>   +#define CLK_MASK_ARM    0x44 >>> +#define MISC_CLK_ENB    0x48 >>> + >>>   #define RST_DFLL_DVCO 0x2f4 >>>   #define DVFS_DFLL_RESET_SHIFT 0 >>>     #define CLK_RST_CONTROLLER_RST_DEV_Y_SET 0x2a8 >>>   #define CLK_RST_CONTROLLER_RST_DEV_Y_CLR 0x2ac >>> +#define CPU_SOFTRST_CTRL 0x380 >>>     #define LVL2_CLK_GATE_OVRA 0xf8 >>>   #define LVL2_CLK_GATE_OVRC 0x3a0 >>> @@ -2825,6 +2829,7 @@ static int tegra210_enable_pllu(void) >>>       struct tegra_clk_pll_freq_table *fentry; >>>       struct tegra_clk_pll pllu; >>>       u32 reg; >>> +    int ret; >>>         for (fentry = pll_u_freq_table; fentry->input_rate; fentry++) { >>>           if (fentry->input_rate == pll_ref_freq) >>> @@ -2853,9 +2858,14 @@ static int tegra210_enable_pllu(void) >>>       reg |= PLL_ENABLE; >>>       writel(reg, clk_base + PLLU_BASE); >>>   -    readl_relaxed_poll_timeout_atomic(clk_base + PLLU_BASE, reg, >>> -                      reg & PLL_BASE_LOCK, 2, 1000); >>> -    if (!(reg & PLL_BASE_LOCK)) { >>> +    /* >>> +     * During clocks resume, same PLLU init and enable sequence get >>> +     * executed. So, readx_poll_timeout_atomic can't be used here as it >>> +     * uses ktime_get() and timekeeping resume doesn't happen by that >>> +     * time. So, using tegra210_wait_for_mask for PLL LOCK. >>> +     */ >>> +    ret = tegra210_wait_for_mask(&pllu, PLLU_BASE, PLL_BASE_LOCK); >>> +    if (ret) { >>>           pr_err("Timed out waiting for PLL_U to lock\n"); >>>           return -ETIMEDOUT; >>>       } >>> @@ -3288,6 +3298,84 @@ static void tegra210_disable_cpu_clock(u32 cpu) >>>   } >>>     #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? >> >>> +    0x23282006, >>> +    0x782e0c18, >>> +    0x0c012c05, >>> +    0x003e7304, >>> +    0x86c04800, >>> +    0xc0199000, >>> +    0x03e03800, >>> +}; >>> + >>> +#define car_readl(_base, _off) readl_relaxed(clk_base + (_base) + ((_off) * 4)) >>> +#define car_writel(_val, _base, _off) \ >>> +        writel_relaxed(_val, clk_base + (_base) + ((_off) * 4)) >>> + >>> +static u32 spare_reg_ctx, misc_clk_enb_ctx, clk_msk_arm_ctx; >>> +static u32 cpu_softrst_ctx[3]; >>> + >>> +static int tegra210_clk_suspend(void) >>> +{ >>> +    unsigned int i; >>> + >>> +    clk_save_context(); >>> + >>> +    /* >>> +     * Save the bootloader configured clock registers SPARE_REG0, >>> +     * MISC_CLK_ENB, CLK_MASK_ARM, CPU_SOFTRST_CTRL. >>> +     */ >>> +    spare_reg_ctx = readl_relaxed(clk_base + SPARE_REG0); >>> +    misc_clk_enb_ctx = readl_relaxed(clk_base + MISC_CLK_ENB); >>> +    clk_msk_arm_ctx = readl_relaxed(clk_base + CLK_MASK_ARM); >>> + >>> +    for (i = 0; i < ARRAY_SIZE(cpu_softrst_ctx); i++) >>> +        cpu_softrst_ctx[i] = car_readl(CPU_SOFTRST_CTRL, i); >>> + >>> +    tegra_clk_periph_suspend(); >>> +    return 0; >>> +} >>> + >>> +static void tegra210_clk_resume(void) >>> +{ >>> +    unsigned int i; >>> + >>> +    tegra_clk_osc_resume(clk_base); >>> + >>> +    /* >>> +     * Restore the bootloader configured clock registers SPARE_REG0, >>> +     * MISC_CLK_ENB, CLK_MASK_ARM, CPU_SOFTRST_CTRL from saved context. >>> +     */ >>> +    writel_relaxed(spare_reg_ctx, clk_base + SPARE_REG0); >>> +    writel_relaxed(misc_clk_enb_ctx, clk_base + MISC_CLK_ENB); >>> +    writel_relaxed(clk_msk_arm_ctx, clk_base + CLK_MASK_ARM); >>> + >>> +    for (i = 0; i < ARRAY_SIZE(cpu_softrst_ctx); i++) >>> +        car_writel(cpu_softrst_ctx[i], CPU_SOFTRST_CTRL, i); >>> + >>> +    fence_udelay(5, clk_base); >>> + >>> +    /* enable all the clocks before changing the clock sources */ >>> +    tegra_clk_periph_force_on(periph_clk_rsvd_mask); >> Why clocks need to be enabled before changing the sources? > > To prevent glitchless frequency switch, Tegra clock programming recommended sequence is to > change MUX control or divisor or both with the clocks running. This should be explained in the comment. > Actual state of clocks before suspend are restored later after all PLL's and peripheral > clocks are restored. > >> >>> +    /* wait for all writes to happen to have all the clocks enabled */ >>> +    wmb(); >> fence_udelay() has exactly the same barrier at the very beginning of readl(), no need to >> duplicate it here. Actually, readl does the rmb() and it should be a more correct variant of fencing because it actually ensures that the write reached hardware. I suppose that something like fence_udelay should be used for the pinctrl as well. >>> +    fence_udelay(2, clk_base); >>> + >>> +    /* restore PLLs and all peripheral clock rates */ >>> +    tegra210_init_pllu(); >> Why USB PLL need to be restored at first? > USB PLL restore is independent to all other clocks restore. So this can be done either > before clk_restore_context or even after. Then why not to implement restore_context for PLLU? >>> +    clk_restore_context(); >>> + >>> +    /* restore all peripheral clocks enable and reset state */ >>> +    tegra_clk_periph_resume(); >>> +} >> [snip]