On Mon, Dec 16, 2024 at 10:00:27AM +0100, Christian Bruel wrote:

[...]

quoted

quoted

+		msleep(PCIE_T_RRS_READY_MS);
+
+	return ret;
+}
+
+static void stm32_pcie_stop_link(struct dw_pcie *pci)
+{
+	struct stm32_pcie *stm32_pcie = to_stm32_pcie(pci);
+
+	regmap_update_bits(stm32_pcie->regmap, SYSCFG_PCIECR,
+			   STM32MP25_PCIECR_LTSSM_EN, 0);
+
+	/* Assert PERST# */
+	if (stm32_pcie->perst_gpio)
+		gpiod_set_value(stm32_pcie->perst_gpio, 1);

I don't like tying PERST# handling with start/stop link. PERST# should be
handled based on the power/clock state.

I don't understand your point: We turn off the PHY in suspend_noirq(), so
that seems a logical place to de-assert in resume_noirq after the refclk is
ready. PERST# should be kept active until the PHY stablilizes the clock in
resume. From the PCIe electromechanical specs, PERST# goes active while the
refclk is not stable/

While your understanding about PERST# is correct, your implementation is not.
You are toggling PERST# from start/stop link callbacks which are supposed to
control the LTSSM state only. I don't have issues with toggling PERST# in
stm32_pcie_{suspend/resume}_noirq().

quoted

quoted

+}
+
+static int stm32_pcie_suspend(struct device *dev)
+{
+	struct stm32_pcie *stm32_pcie = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev) || device_wakeup_path(dev))
+		enable_irq_wake(stm32_pcie->wake_irq);
+
+	return 0;
+}
+
+static int stm32_pcie_resume(struct device *dev)
+{
+	struct stm32_pcie *stm32_pcie = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev) || device_wakeup_path(dev))
+		disable_irq_wake(stm32_pcie->wake_irq);
+
+	return 0;
+}
+
+static int stm32_pcie_suspend_noirq(struct device *dev)
+{
+	struct stm32_pcie *stm32_pcie = dev_get_drvdata(dev);
+
+	stm32_pcie->link_is_up = dw_pcie_link_up(stm32_pcie->pci);
+
+	stm32_pcie_stop_link(stm32_pcie->pci);

I don't understand how endpoint can wakeup the host if PERST# gets asserted.

The stm32 PCIe doesn't support L2, we don't expect an in-band beacon for the
wakeup. We support wakeup only from sideband WAKE#, that will restart the
link from IRQ

I don't understand how WAKE# is supported without L2. Only in L2 state, endpoint
will make use of Vaux and it will wakeup the host using either beacon or WAKE#.
If you don't support L2, then the endpoint will reach L3 (link off) state.

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+	clk_disable_unprepare(stm32_pcie->clk);
+
+	if (!device_may_wakeup(dev) && !device_wakeup_path(dev))
+		phy_exit(stm32_pcie->phy);
+
+	return pinctrl_pm_select_sleep_state(dev);
+}
+
+static int stm32_pcie_resume_noirq(struct device *dev)
+{
+	struct stm32_pcie *stm32_pcie = dev_get_drvdata(dev);
+	struct dw_pcie *pci = stm32_pcie->pci;
+	struct dw_pcie_rp *pp = &pci->pp;
+	int ret;
+
+	/* init_state must be called first to force clk_req# gpio when no

CLKREQ#

Why RC should control CLKREQ#?

REFCLK is gated with CLKREQ#, So we cannot access the core
without CLKREQ# if no device is present. So force it with a init pinmux
the time to init the PHY and the core DBI registers

Ok. You should add a comment to clarify it in the code as this is not a standard
behavior.

quoted

Also please use preferred style for multi-line comments:

	/*
	 * ...
	 */

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+	 * device is plugged.
+	 */
+	if (!IS_ERR(dev->pins->init_state))
+		ret = pinctrl_select_state(dev->pins->p, dev->pins->init_state);
+	else
+		ret = pinctrl_pm_select_default_state(dev);
+
+	if (ret) {
+		dev_err(dev, "Failed to activate pinctrl pm state: %d\n", ret);
+		return ret;
+	}
+
+	if (!device_may_wakeup(dev) && !device_wakeup_path(dev)) {
+		ret = phy_init(stm32_pcie->phy);
+		if (ret) {
+			pinctrl_pm_select_default_state(dev);
+			return ret;
+		}
+	}
+
+	ret = clk_prepare_enable(stm32_pcie->clk);
+	if (ret)
+		goto clk_err;

Please name the goto labels of their purpose. Like err_phy_exit.

OK

quoted

quoted

+
+	ret = dw_pcie_setup_rc(pp);
+	if (ret)
+		goto pcie_err;

This should be, 'err_disable_clk'.

quoted

+
+	if (stm32_pcie->link_is_up) {

Why do you need this check? You cannot start the link in the absence of an
endpoint?

It is an optimization to avoid unnecessary "dw_pcie_wait_for_link" if no
device is present during suspend

In that case you'll not trigger LTSSM if there was no endpoint connected before
suspend. What if users connect an endpoint after resume?

- Mani

-- 
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