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

From: Sowjanya Komatineni
Date: Mon Aug 12 2019 - 15:03:11 EST


On 8/12/19 11:19 AM, Dmitry Osipenko wrote:
12.08.2019 20:28, Sowjanya Komatineni ÐÐÑÐÑ:
On 8/12/19 9:25 AM, Dmitry Osipenko wrote:
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>
---
ÂÂÂ drivers/clk/tegra/clk-tegra210.c | 103 +++++++++++++++++++++++++++++++++++++--
ÂÂÂ drivers/clk/tegra/clk.cÂÂÂÂÂÂÂÂÂ |Â 64 ++++++++++++++++++++++++
ÂÂÂ drivers/clk/tegra/clk.hÂÂÂÂÂÂÂÂÂ |ÂÂ 3 ++
ÂÂÂ 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 @@
ÂÂÂ #include <linux/clkdev.h>
ÂÂÂ #include <linux/of.h>
ÂÂÂ #include <linux/of_address.h>
+#include <linux/syscore_ops.h>
ÂÂÂ #include <linux/delay.h>
ÂÂÂ #include <linux/export.h>
ÂÂÂ #include <linux/mutex.h>
ÂÂÂ #include <linux/clk/tegra.h>
ÂÂÂ #include <dt-bindings/clock/tegra210-car.h>
ÂÂÂ #include <dt-bindings/reset/tegra210-car.h>
-#include <linux/iopoll.h>
ÂÂÂ #include <linux/sizes.h>
ÂÂÂ #include <soc/tegra/pmc.h>
ÂÂÂ @@ -220,11 +220,15 @@
ÂÂÂ #define CLK_M_DIVISOR_SHIFT 2
ÂÂÂ #define CLK_M_DIVISOR_MASK 0x3
ÂÂÂ +#define CLK_MASK_ARMÂÂÂ 0x44
+#define MISC_CLK_ENBÂÂÂ 0x48
+
ÂÂÂ #define RST_DFLL_DVCO 0x2f4
ÂÂÂ #define DVFS_DFLL_RESET_SHIFT 0
ÂÂÂ Â #define CLK_RST_CONTROLLER_RST_DEV_Y_SET 0x2a8
ÂÂÂ #define CLK_RST_CONTROLLER_RST_DEV_Y_CLR 0x2ac
+#define CPU_SOFTRST_CTRL 0x380
ÂÂÂ Â #define LVL2_CLK_GATE_OVRA 0xf8
ÂÂÂ #define LVL2_CLK_GATE_OVRC 0x3a0
@@ -2825,6 +2829,7 @@ static int tegra210_enable_pllu(void)
ÂÂÂÂÂÂÂ struct tegra_clk_pll_freq_table *fentry;
ÂÂÂÂÂÂÂ struct tegra_clk_pll pllu;
ÂÂÂÂÂÂÂ u32 reg;
+ÂÂÂ int ret;
ÂÂÂ ÂÂÂÂÂ for (fentry = pll_u_freq_table; fentry->input_rate; fentry++) {
ÂÂÂÂÂÂÂÂÂÂÂ if (fentry->input_rate == pll_ref_freq)
@@ -2853,9 +2858,14 @@ static int tegra210_enable_pllu(void)
ÂÂÂÂÂÂÂ reg |= PLL_ENABLE;
ÂÂÂÂÂÂÂ writel(reg, clk_base + PLLU_BASE);
ÂÂÂ -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) {
ÂÂÂÂÂÂÂÂÂÂÂ pr_err("Timed out waiting for PLL_U to lock\n");
ÂÂÂÂÂÂÂÂÂÂÂ return -ETIMEDOUT;
ÂÂÂÂÂÂÂ }
@@ -3288,6 +3298,84 @@ static void tegra210_disable_cpu_clock(u32 cpu)
ÂÂÂ }
ÂÂÂ 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)?

[snip]
yes all reserved bits of clk_enb register is 0. This should not be set to 1.

As I will be changing to variable name to valid_mask instead of reserved mask, will also
change values to valid mask so it can be used directly to write to clk_enb for enabling all
peripherals clks.

It looks to me that the tegra_clk_periph_force_on() could be made local to the
clk-tegra210.c and then the raw clk_enb values could be written directly instead of having
the clk_enb[] array, probably that will be a bit cleaner

All CLK_OUT_ENB* registers are already defined in clk driver and also periph_regs includes all of these to use.

To write value to enable all clocks directly without array, it need total 7 individual register writes for Tegra210. Also when suspend/resume is implemented for other prior tegras, they need to do same in tegra clock driver.

Reason I had this in clock driver is, this can be used by all tegra clock drivers and just can pass valid clocks values.

But doing individual register write with direct hard code values in corresponding tegra clock driver is preferred still, will update so in next revision and will move all the CLK_OUT_ENB* register defines to tegra/clk.h

Currently RST_DEVICES & CLK_OUT_ENB are all in tegra/clk.c

.