soc/intel/common/block/pcie/rtd3: Add optional _OFF and _ON skip control

- Optional feature to provide mechanism to skip _OFF and _On execution.
- It is used for the device to skip _OFF and _ON during device driver
  reload.
- OFSK is used to skip _OFF Method at the end of device driver removal.
- ONSK is used to skip _ON Method at the beginning of driver loading.
- General flow use case:
  1. Device driver is removed by 'rmmod' command.
  2. Device _RST is called. _RST perform reset.
  3. Device increments OFSK in _RST to skip the following _OFF invoked by
     OSPM.
  4. OSPM invokes _OFF at the end of driver removal.
  5. _OFF sees OFSK and skips current execution and decrements OFSK so that
     _OFF will be executed normally next time.
  6. _OFF increments ONSK to skip the following _ON invoked by OSPM.
  7. Device driver is reloaded by 'insmod/modprobe' command.
  8. OSPM invokes _ON at the beginning of driver loading.
  9. _ON sees ONSK and skip current execution and decrements ONSK so that
     _ON will be executed normally next time.

- In normal case:
When suspend, OSPM invokes _OFF. Since OFSK is zero, the device goes
to deeper state as expected.

When resume, OSPM invokes _ON. Sinc ONSK is zero, the device goes
to active state as expected.

- Generated changes:

        PowerResource (RTD3, 0x00, 0x0000)
            Name (ONSK, Zero)
            Name (OFSK, Zero)
            ...

            Method (_ON, 0, Serialized)  // _ON_: Power On
            {
                If ((ONSK == Zero))
                {
                    ...
                }
                Else
                {
                    ONSK--
                }
                        }

            Method (_OFF, 0, Serialized)  // _OFF: Power Off
            {
               If ((OFSK == Zero))
                {
                    ...
                }
                Else
                {
                    OFSK--
                    ONSK++
                }
            }

Test:
Enable and verify OFSK and ONSK Name objects and the if-condition logic
inside _OFF and _ON methods is added.

Signed-off-by: Cliff Huang <cliff.huang@intel.com>
Change-Id: Ic32d151d65107bfc220258c383a575e40a496b6f
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61353
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/soc/intel/common/block/pcie/rtd3/chip.h

@@ -76,6 +76,12 @@ struct soc_intel_common_block_pcie_rtd3_config {
 	 *-----------------------------------------------------------------------------------*
 	 */
 	enum acpi_pcie_rp_pm_emit ext_pm_support;
+
+	/*
+	 * Add support to skip _OFF and _ON execution when needed, such as reloading
+	 * the device driver.
+	 */
+	bool skip_on_off_support;
 };
 
 #endif /* __SOC_INTEL_COMMON_BLOCK_PCIE_RTD3_CHIP_H__ */

src/soc/intel/common/block/pcie/rtd3/rtd3.c

@@ -147,6 +147,13 @@ pcie_rtd3_acpi_method_on(unsigned int pcie_rp,
 {
 	acpigen_write_method_serialized("_ON", 0);
 
+	/* When this feature is enabled, ONSK indicates if the previous _OFF was
+	 * skipped. If so, since the device was not in Off state, and the current
+	 * _ON can be skipped as well.
+	 */
+	if (config->skip_on_off_support)
+		acpigen_write_if_lequal_namestr_int("ONSK", 0);
+
 	/* Disable modPHY power gating for PCH RPs. */
 	if (rp_type == PCIE_RP_PCH)
 		pcie_rtd3_enable_modphy_pg(pcie_rp, PG_DISABLE);
@@ -173,6 +180,16 @@ pcie_rtd3_acpi_method_on(unsigned int pcie_rp,
 	if (!config->disable_l23)
 		pcie_rtd3_acpi_l23_exit();
 
+	if (config->skip_on_off_support) {
+		/* If current _ON is skipped, ONSK is decremented so that _ON will be
+		 * executed normally until _OFF is skipped again.
+		 */
+		acpigen_write_else();
+		acpigen_emit_byte(DECREMENT_OP);
+		acpigen_emit_namestring("ONSK");
+
+		acpigen_pop_len(); /* Else */
+	}
 	acpigen_pop_len(); /* Method */
 }
 
@@ -183,6 +200,14 @@ pcie_rtd3_acpi_method_off(int pcie_rp,
 {
 	acpigen_write_method_serialized("_OFF", 0);
 
+	/* When this feature is enabled, ONSK is checked to see if the device
+	 * wants _OFF to be skipped for once. ONSK is normally incremented in the
+	 * device method, such as reset _RST, which is invoked during driver reload.
+	 * In such case, _OFF needs to be avoided at the end of driver removal.
+	 */
+	if (config->skip_on_off_support)
+		acpigen_write_if_lequal_namestr_int("OFSK", 0);
+
 	/* Trigger L23 ready entry flow unless disabled by config. */
 	if (!config->disable_l23)
 		pcie_rtd3_acpi_l23_entry();
@@ -209,6 +234,22 @@ pcie_rtd3_acpi_method_off(int pcie_rp,
 			acpigen_write_sleep(config->enable_off_delay_ms);
 	}
 
+	if (config->skip_on_off_support) {
+		/* If current _OFF is skipped, ONSK is incremented so that the
+		 * following _ON will also be skipped. In addition, OFSK is decremented
+		 * so that next _OFF will be executed normally until the device method
+		 * increments OFSK again.
+		 */
+		acpigen_write_else();
+		/* OFSK-- */
+		acpigen_emit_byte(DECREMENT_OP);
+		acpigen_emit_namestring("OFSK");
+		/* ONSK++ */
+		acpigen_emit_byte(INCREMENT_OP);
+		acpigen_emit_namestring("ONSK");
+
+		acpigen_pop_len(); /* Else */
+	}
 	acpigen_pop_len(); /* Method */
 }
 
@@ -391,6 +432,21 @@ static void pcie_rtd3_acpi_fill_ssdt(const struct device *dev)
 
 	/* ACPI Power Resource for controlling the attached device power. */
 	acpigen_write_power_res("RTD3", 0, 0, power_res_states, ARRAY_SIZE(power_res_states));
+
+	if (config->skip_on_off_support) {
+		/* OFSK:  0 = _OFF Method will be executed normally when called;
+		 *       >1 = _OFF will be skipped.
+		 *       _OFF Method to decrement OFSK and increment ONSK if the
+		 *       current execution is skipped.
+		 * ONSK:  0 = _ON Method will be executed normally when called;
+		 *       >1 = _ONF will be skipped.
+		 *       _ON Method to decrement ONSK if the current execution is
+		 *       skipped.
+		 */
+		acpigen_write_name_integer("ONSK", 0);
+		acpigen_write_name_integer("OFSK", 0);
+	}
+
 	pcie_rtd3_acpi_method_status(config);
 	pcie_rtd3_acpi_method_on(pcie_rp, config, rp_type);
 	pcie_rtd3_acpi_method_off(pcie_rp, config, rp_type);