Re: [PATCH V5 11/18] clk: tegra210: Add support for Tegra210 clocks

Sowjanya Komatineni
2019-07-13T05:54:19Z

On 6/29/19 8:10 AM, Dmitry Osipenko wrote:
> 28.06.2019 5:12, Sowjanya Komatineni пишет:
>> This patch adds system suspend and resume support for Tegra210
>> clocks.
>>
>> All the CAR controller settings are lost on suspend when core power
>> goes off.
>>
>> This patch has implementation for saving and restoring all the PLLs
>> and clocks context during system suspend and resume to have the
>> clocks back to same state for normal operation.
>>
>> Acked-by: Thierry Reding <treding@nvidia.com>
>> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
>> ---
>> drivers/clk/tegra/clk-tegra210.c | 115 ++++++++++++++++++++++++++++++++++++++-
>> drivers/clk/tegra/clk.c | 14 +++++
>> drivers/clk/tegra/clk.h | 1 +
>> 3 files changed, 127 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/clk/tegra/clk-tegra210.c b/drivers/clk/tegra/clk-tegra210.c
>> index 1c08c53482a5..1b839544e086 100644
>> --- a/drivers/clk/tegra/clk-tegra210.c
>> +++ b/drivers/clk/tegra/clk-tegra210.c
>> @@ -9,10 +9,12 @@
>> #include <linux/clkdev.h>
>> #include <linux/of.h>
>> #include <linux/of_address.h>
>> +#include <linux/of_platform.h>
>> #include <linux/delay.h>
>> #include <linux/export.h>
>> #include <linux/mutex.h>
>> #include <linux/clk/tegra.h>
>> +#include <linux/syscore_ops.h>
>> #include <dt-bindings/clock/tegra210-car.h>
>> #include <dt-bindings/reset/tegra210-car.h>
>> #include <linux/iopoll.h>
>> @@ -20,6 +22,7 @@
>> #include <soc/tegra/pmc.h>
>>
>> #include "clk.h"
>> +#include "clk-dfll.h"
>> #include "clk-id.h"
>>
>> /*
>> @@ -225,6 +228,7 @@
>>
>> #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
>> @@ -2820,6 +2824,7 @@ 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)
>> @@ -2847,10 +2852,10 @@ static int tegra210_enable_pllu(void)
>> fence_udelay(1, clk_base);
>> reg |= PLL_ENABLE;
>> writel(reg, clk_base + PLLU_BASE);
>> + fence_udelay(1, clk_base);
>>
>> - readl_relaxed_poll_timeout_atomic(clk_base + PLLU_BASE, reg,
>> - reg & PLL_BASE_LOCK, 2, 1000);
>> - if (!(reg & PLL_BASE_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;
>> }
>> @@ -3283,6 +3288,103 @@ static void tegra210_disable_cpu_clock(u32 cpu)
>> }
>>
>> #ifdef CONFIG_PM_SLEEP
>> +static u32 cpu_softrst_ctx[3];
>> +static struct platform_device *dfll_pdev;
>> +#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 int tegra210_clk_suspend(void)
>> +{
>> + unsigned int i;
>> + struct device_node *node;
>> +
>> + tegra_cclkg_burst_policy_save_context();
>> +
>> + if (!dfll_pdev) {
>> + node = of_find_compatible_node(NULL, NULL,
>> + "nvidia,tegra210-dfll");
>> + if (node)
>> + dfll_pdev = of_find_device_by_node(node);
>> +
>> + of_node_put(node);
>> + if (!dfll_pdev)
>> + pr_err("dfll node not found. no suspend for dfll\n");
>> + }
>> +
>> + if (dfll_pdev)
>> + tegra_dfll_suspend(dfll_pdev);
>> +
>> + /* Enable PLLP_OUT_CPU after dfll suspend */
>> + tegra_clk_set_pllp_out_cpu(true);
>> +
>> + tegra_sclk_cclklp_burst_policy_save_context();
>> +
>> + clk_save_context();
>> +
>> + for (i = 0; i < ARRAY_SIZE(cpu_softrst_ctx); i++)
>> + cpu_softrst_ctx[i] = car_readl(CPU_SOFTRST_CTRL, i);
>> +
>> + return 0;
>> +}
>> +
>> +static void tegra210_clk_resume(void)
>> +{
>> + unsigned int i;
>> + struct clk_hw *parent;
>> + struct clk *clk;
>> +
>> + /*
>> + * clk_restore_context restores clocks as per the clock tree.
>> + *
>> + * dfllCPU_out is first in the clock tree to get restored and it
>> + * involves programming DFLL controller along with restoring CPUG
>> + * clock burst policy.
>> + *
>> + * DFLL programming needs dfll_ref and dfll_soc peripheral clocks
>> + * to be restores which are part ofthe peripheral clocks.
>> + * So, peripheral clocks restore should happen prior to dfll clock
>> + * restore.
>> + */
>> +
>> + tegra_clk_osc_resume(clk_base);
>> + for (i = 0; i < ARRAY_SIZE(cpu_softrst_ctx); i++)
>> + car_writel(cpu_softrst_ctx[i], CPU_SOFTRST_CTRL, i);
>> +
>> + /* restore all plls and peripheral clocks */
>> + tegra210_init_pllu();
>> + clk_restore_context();
>> +
>> + fence_udelay(5, clk_base);
>> +
>> + /* resume SCLK and CPULP clocks */
>> + tegra_sclk_cpulp_burst_policy_restore_context();
>> +
>> + /*
>> + * restore CPUG clocks:
>> + * - enable DFLL in open loop mode
>> + * - switch CPUG to DFLL clock source
>> + * - close DFLL loop
>> + * - sync PLLX state
>> + */
>> + if (dfll_pdev)
>> + tegra_dfll_resume(dfll_pdev, false);
>> +
>> + tegra_cclkg_burst_policy_restore_context();
>> + fence_udelay(2, clk_base);
>> +
>> + if (dfll_pdev)
>> + tegra_dfll_resume(dfll_pdev, true);
>> +
>> + parent = clk_hw_get_parent(__clk_get_hw(clks[TEGRA210_CLK_CCLK_G]));
>> + clk = clks[TEGRA210_CLK_PLL_X];
>> + if (parent != __clk_get_hw(clk))
>> + tegra_clk_sync_state_pll(__clk_get_hw(clk));
>> +
>> + /* Disable PLL_OUT_CPU after DFLL resume */
>> + tegra_clk_set_pllp_out_cpu(false);
>> +}
>> +
>> static void tegra210_cpu_clock_suspend(void)
>> {
>> /* switch coresite to clk_m, save off original source */
>> @@ -3298,6 +3400,11 @@ static void tegra210_cpu_clock_resume(void)
>> }
>> #endif
>>
>> +static struct syscore_ops tegra_clk_syscore_ops = {
>> + .suspend = tegra210_clk_suspend,
>> + .resume = tegra210_clk_resume,
>> +};
>> +
>> static struct tegra_cpu_car_ops tegra210_cpu_car_ops = {
>> .wait_for_reset = tegra210_wait_cpu_in_reset,
>> .disable_clock = tegra210_disable_cpu_clock,
>> @@ -3583,5 +3690,7 @@ static void __init tegra210_clock_init(struct device_node *np)
>> tegra210_mbist_clk_init();
>>
>> tegra_cpu_car_ops = &tegra210_cpu_car_ops;
>> +
>> + register_syscore_ops(&tegra_clk_syscore_ops);
>> }
> Is it really worthwhile to use syscore_ops for suspend/resume given that drivers for
> won't resume before the CLK driver anyway? Are there any other options for CLK
> suspend/resume?
>
> I'm also not sure whether PM runtime API could be used at all in the context of
> syscore_ops ..
>
> Secondly, what about to use generic clk_save_context() / clk_restore_context()
> helpers for the suspend-resume? It looks to me that some other essential (and proper)
> platform driver (soc/tegra/? PMC?) should suspend-resume the clocks using the generic
> CLK Framework API.

Clock resume should happen very early to restore peripheral and cpu
clocks very early than peripheral drivers resume happens.

this patch series uses clk_save_context and clk_restore_context for
corresponding divider, pll, pllout.. save and restore context.

But as there is dependency on dfll resume and cpu and pllx clocks
restore, couldnt use clk_save_context and clk_restore_context for dfll.

So implemented recommended dfll resume sequence in main Tegra210 clock
driver along with invoking clk_save_context/clk_restore_context where
all other clocks save/restore happens as per clock tree traversal.