Re: [PATCH V3 11/17] clk: tegra210: support for Tegra210 clocks suspend and resume

From: Thierry Reding
Date: Tue Jun 18 2019 - 08:21:15 EST

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In reply to: Sowjanya Komatineni: "[PATCH V3 11/17] clk: tegra210: support for Tegra210 clocks suspend and resume"
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On Tue, Jun 18, 2019 at 12:46:25AM -0700, Sowjanya Komatineni wrote:
> 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
> system back to operating state.
>
> Signed-off-by: Sowjanya Komatineni <skomatineni@xxxxxxxxxx>
> ---
> drivers/clk/tegra/clk-tegra210.c | 218 +++++++++++++++++++++++++++++++++++++--
> 1 file changed, 211 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/clk/tegra/clk-tegra210.c b/drivers/clk/tegra/clk-tegra210.c
> index e1ba62d2b1a0..c34d92e871f4 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"
>
> /*
> @@ -36,6 +39,8 @@
> #define CLK_SOURCE_LA 0x1f8
> #define CLK_SOURCE_SDMMC2 0x154
> #define CLK_SOURCE_SDMMC4 0x164
> +#define CLK_OUT_ENB_Y 0x298
> +#define CLK_ENB_PLLP_OUT_CPU BIT(31)
>
> #define PLLC_BASE 0x80
> #define PLLC_OUT 0x84
> @@ -225,6 +230,7 @@
>
> #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 +2826,7 @@ 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)
> @@ -2836,7 +2843,7 @@ static int tegra210_enable_pllu(void)
> reg = readl_relaxed(clk_base + pllu.params->ext_misc_reg[0]);
> reg &= ~BIT(pllu.params->iddq_bit_idx);
> writel_relaxed(reg, clk_base + pllu.params->ext_misc_reg[0]);
> - udelay(5);
> + fence_udelay(5, clk_base);
>
> reg = readl_relaxed(clk_base + PLLU_BASE);
> reg &= ~GENMASK(20, 0);
> @@ -2844,13 +2851,13 @@ static int tegra210_enable_pllu(void)
> reg |= fentry->n << 8;
> reg |= fentry->p << 16;
> writel(reg, clk_base + PLLU_BASE);
> - udelay(1);
> + fence_udelay(1, clk_base);

These udelay() -> fence_udelay() seem like they should be a separate
patch.

> 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;
> }
> @@ -2890,12 +2897,12 @@ static int tegra210_init_pllu(void)
> reg = readl_relaxed(clk_base + XUSB_PLL_CFG0);
> reg &= ~XUSB_PLL_CFG0_PLLU_LOCK_DLY_MASK;
> writel_relaxed(reg, clk_base + XUSB_PLL_CFG0);
> - udelay(1);
> + fence_udelay(1, clk_base);
>
> reg = readl_relaxed(clk_base + PLLU_HW_PWRDN_CFG0);
> reg |= PLLU_HW_PWRDN_CFG0_SEQ_ENABLE;
> writel_relaxed(reg, clk_base + PLLU_HW_PWRDN_CFG0);
> - udelay(1);
> + fence_udelay(1, clk_base);
>
> reg = readl_relaxed(clk_base + PLLU_BASE);
> reg &= ~PLLU_BASE_CLKENABLE_USB;
> @@ -3282,6 +3289,188 @@ static void tegra210_disable_cpu_clock(u32 cpu)
> }
>
> #ifdef CONFIG_PM_SLEEP
> +static u32 cpu_softrst_ctx[3];
> +static struct platform_device *dfll_pdev;
> +static u32 *periph_clk_src_ctx;
> +struct periph_source_bank {

Blank line between the above two.

> + u32 start;
> + u32 end;
> +};
> +
> +static struct periph_source_bank periph_srcs[] = {
> + [0] = {
> + .start = 0x100,
> + .end = 0x198,
> + },
> + [1] = {
> + .start = 0x1a0,
> + .end = 0x1f8,
> + },
> + [2] = {
> + .start = 0x3b4,
> + .end = 0x42c,
> + },
> + [3] = {
> + .start = 0x49c,
> + .end = 0x4b4,
> + },
> + [4] = {
> + .start = 0x560,
> + .end = 0x564,
> + },
> + [5] = {
> + .start = 0x600,
> + .end = 0x678,
> + },
> + [6] = {
> + .start = 0x694,
> + .end = 0x6a0,
> + },
> + [7] = {
> + .start = 0x6b8,
> + .end = 0x718,
> + },
> +};
> +
> +/* This array lists the valid clocks for each periph clk bank */
> +static u32 periph_clks_on[] = {
> + 0xdcd7dff9,
> + 0x87d1f3e7,
> + 0xf3fed3fa,
> + 0xffc18cfb,
> + 0x793fb7ff,
> + 0x3fe66fff,
> + 0xfc1fc7ff,
> +};

Hm... this is a bunch of magic. Perhaps replace this by a list of the
clock IDs? That's perhaps a little more verbose, but if we ever need to
tweak the list of IDs in that periph_clks_on array, that'll be quite the
challenge.

Also, is this list a "guess" or are these all guaranteed to be always
on? What if some of these ended up getting disabled as part of suspend
already (by their users). If we force them on, won't their references
become unbalanced if the driver later enables them again on resume?

> +
> +static struct platform_device *dfll_pdev;

I think you already predeclared this one above.

> +#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 * __init tegra210_init_suspend_ctx(void)
> +{
> + int i, size = 0;

Can both be unsigned int.

> +
> + for (i = 0; i < ARRAY_SIZE(periph_srcs); i++)
> + size += periph_srcs[i].end - periph_srcs[i].start + 4;
> +
> + periph_clk_src_ctx = kmalloc(size, GFP_KERNEL);
> +
> + return periph_clk_src_ctx;

It's somewhat wasteful to return a global variable since you can access
it anyway. Perhaps it'd be more useful to make the function return a
boolean?

> +}
> +
> +static int tegra210_clk_suspend(void)
> +{
> + int i;

unsigned int.

> + unsigned long off;
> + struct device_node *node;
> + u32 *clk_rst_ctx = periph_clk_src_ctx;
> + u32 val;
> +
> + 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");
> + }

Wouldn't it make sense to run this only once, perhaps as part of
tegra210_init_suspend_ctx()?

> +
> + if (dfll_pdev)
> + tegra_dfll_suspend(dfll_pdev);
> +
> + /* Enable PLLP_OUT_CPU after dfll suspend */
> + val = car_readl(CLK_OUT_ENB_Y, 0);
> + val |= CLK_ENB_PLLP_OUT_CPU;
> + car_writel(val, CLK_OUT_ENB_Y, 0);
> +
> + tegra_clk_periph_suspend(clk_base);
> +
> + for (i = 0; i < ARRAY_SIZE(periph_srcs); i++)
> + for (off = periph_srcs[i].start; off <= periph_srcs[i].end;
> + off += 4)
> + *clk_rst_ctx++ = car_readl(off, 0);
> +
> + tegra_sclk_cclklp_burst_policy_save_context();
> +
> + for (i = 0; i < ARRAY_SIZE(cpu_softrst_ctx); i++)
> + cpu_softrst_ctx[i] = car_readl(CPU_SOFTRST_CTRL, i);
> +
> + clk_save_context();
> +
> + return 0;
> +}
> +
> +static void tegra210_clk_resume(void)
> +{
> + int i;
> + unsigned long off;
> + u32 val;
> + u32 *clk_rst_ctx = periph_clk_src_ctx;
> + struct clk_hw *parent;
> + struct clk *clk;
> +
> + for (i = 0; i < ARRAY_SIZE(cpu_softrst_ctx); i++)
> + car_writel(cpu_softrst_ctx[i], CPU_SOFTRST_CTRL, i);
> +
> + tegra_clk_osc_resume(clk_base);
> +
> + /*
> + * restore all the plls before configuring clocks and resetting
> + * the devices.
> + */
> + tegra210_init_pllu();
> + tegra_sclk_cpulp_burst_policy_restore_context();
> + clk_restore_context();
> +
> + /* enable all clocks before configuring clock sources */
> + tegra_clk_periph_force_on(periph_clks_on, ARRAY_SIZE(periph_clks_on),
> + clk_base);
> + /* wait for all writes to happen to have all the clocks enabled */
> + wmb();
> + fence_udelay(2, clk_base);
> +
> + /* restore all the devices clock sources */
> + for (i = 0; i < ARRAY_SIZE(periph_srcs); i++)
> + for (off = periph_srcs[i].start; off <= periph_srcs[i].end;
> + off += 4)
> + car_writel(*clk_rst_ctx++, off, 0);
> +
> + /* propagate and restore resets, restore clock state */
> + fence_udelay(5, clk_base);
> + tegra_clk_periph_resume(clk_base);
> +
> + /*
> + * 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 */
> + val = car_readl(CLK_OUT_ENB_Y, 0);
> + val &= ~CLK_ENB_PLLP_OUT_CPU;
> + car_writel(val, CLK_OUT_ENB_Y, 0);
> +}

I'm surprised by the amount of work that we need to do here. I had hoped
that the clock framework's save/restore infrastructure would be enough.
I suppose you do call clk_restore_context() somewhere in there, so maybe
this really is as good as it gets.

Thierry

> +
> static void tegra210_cpu_clock_suspend(void)
> {
> /* switch coresite to clk_m, save off original source */
> @@ -3295,8 +3484,20 @@ static void tegra210_cpu_clock_resume(void)
> writel(tegra210_cpu_clk_sctx.clk_csite_src,
> clk_base + CLK_SOURCE_CSITE);
> }
> +#else
> +#define tegra210_clk_suspend NULL
> +#define tegra210_clk_resume NULL
> +static inline u32 *tegra210_init_suspend_ctx(void)
> +{
> + return NULL;
> +}
> #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,
> @@ -3580,5 +3781,8 @@ static void __init tegra210_clock_init(struct device_node *np)
> tegra210_mbist_clk_init();
>
> tegra_cpu_car_ops = &tegra210_cpu_car_ops;
> +
> + if (tegra210_init_suspend_ctx())
> + register_syscore_ops(&tegra_clk_syscore_ops);
> }
> CLK_OF_DECLARE(tegra210, "nvidia,tegra210-car", tegra210_clock_init);
> --
> 2.7.4
>

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