Re: [PATCH v2 2/3] PCI: dwc: Add Qualcomm PCIe Endpoint controller driver

[Stanimir Varbanov <svarbanov@mm-sol.com>]

Hi Mani,

On 6/3/21 1:38 PM, Manivannan Sadhasivam wrote:
> Add driver support for Qualcomm PCIe Endpoint controller driver based on
> the Designware core with added Qualcomm specific wrapper around the
> core. The driver support is very basic such that it supports only
> enumeration, PCIe read/write, and MSI. There is no ASPM and PM support
> for now but these will be added later.
> 
> The driver is capable of using the PERST# and WAKE# side-band GPIOs for
> operation and written on top of the DWC PCI framework.
> 
> Co-developed-by: Siddartha Mohanadoss <smohanad@codeaurora.org>
> Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>
> [mani: restructured the driver and fixed several bugs for upstream]
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> ---
>  drivers/pci/controller/dwc/Kconfig        |  10 +
>  drivers/pci/controller/dwc/Makefile       |   1 +
>  drivers/pci/controller/dwc/pcie-qcom-ep.c | 780 ++++++++++++++++++++++
>  3 files changed, 791 insertions(+)
>  create mode 100644 drivers/pci/controller/dwc/pcie-qcom-ep.c
> 
> diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
> index 423d35872ce4..32e735b1fd85 100644
> --- a/drivers/pci/controller/dwc/Kconfig
> +++ b/drivers/pci/controller/dwc/Kconfig
> @@ -180,6 +180,16 @@ config PCIE_QCOM
>  	  PCIe controller uses the DesignWare core plus Qualcomm-specific
>  	  hardware wrappers.
>  
> +config PCIE_QCOM_EP
> +	bool "Qualcomm PCIe controller - Endpoint mode"
> +	depends on OF && (ARCH_QCOM || COMPILE_TEST)
> +	depends on PCI_ENDPOINT
> +	select PCIE_DW_EP

Do you see a problem if root-complex driver and EP drive are enabled on
the same time? I think the PCIe IP can work only on one of both modes.

> +	help
> +	  Say Y here to enable support for the PCIe controllers on Qualcomm SoCs
> +	  to work in endpoint mode. The PCIe controller uses the DesignWare core
> +	  plus Qualcomm-specific hardware wrappers.
> +
>  config PCIE_ARMADA_8K
>  	bool "Marvell Armada-8K PCIe controller"
>  	depends on ARCH_MVEBU || COMPILE_TEST
> diff --git a/drivers/pci/controller/dwc/Makefile b/drivers/pci/controller/dwc/Makefile
> index eca805c1a023..abb27642d46b 100644
> --- a/drivers/pci/controller/dwc/Makefile
> +++ b/drivers/pci/controller/dwc/Makefile
> @@ -12,6 +12,7 @@ obj-$(CONFIG_PCI_KEYSTONE) += pci-keystone.o
>  obj-$(CONFIG_PCI_LAYERSCAPE) += pci-layerscape.o
>  obj-$(CONFIG_PCI_LAYERSCAPE_EP) += pci-layerscape-ep.o
>  obj-$(CONFIG_PCIE_QCOM) += pcie-qcom.o
> +obj-$(CONFIG_PCIE_QCOM_EP) += pcie-qcom-ep.o
>  obj-$(CONFIG_PCIE_ARMADA_8K) += pcie-armada8k.o
>  obj-$(CONFIG_PCIE_ARTPEC6) += pcie-artpec6.o
>  obj-$(CONFIG_PCIE_INTEL_GW) += pcie-intel-gw.o
> diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c
> new file mode 100644
> index 000000000000..b68511bacc2a
> --- /dev/null
> +++ b/drivers/pci/controller/dwc/pcie-qcom-ep.c
> @@ -0,0 +1,780 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Qualcomm PCIe Endpoint controller driver
> + *
> + * Copyright (c) 2020, The Linux Foundation. All rights reserved.
> + * Author: Siddartha Mohanadoss <smohanad@codeaurora.org
> + *
> + * Copyright (c) 2021, Linaro Ltd.
> + * Author: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/platform_device.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/reset.h>
> +#include <linux/delay.h>
> +#include <linux/phy/phy.h>
> +#include <linux/pm_domain.h>
> +
> +#include "pcie-designware.h"
> +
> +/* PARF registers */
> +#define PARF_SYS_CTRL				0x00
> +#define PARF_DB_CTRL				0x10
> +#define PARF_PM_CTRL				0x20
> +#define PARF_DEBUG_INT_EN			0x190
> +#define PARF_AXI_MSTR_RD_HALT_NO_WRITES		0x1a4
> +#define PARF_AXI_MSTR_WR_ADDR_HALT		0x1a8
> +#define PARF_Q2A_FLUSH				0x1aC
> +#define PARF_LTSSM				0x1b0
> +#define PARF_CFG_BITS				0x210
> +#define PARF_INT_ALL_STATUS			0x224
> +#define PARF_INT_ALL_CLEAR			0x228
> +#define PARF_INT_ALL_MASK			0x22c
> +#define PARF_SLV_ADDR_MSB_CTRL			0x2c0
> +#define PARF_DBI_BASE_ADDR			0x350
> +#define PARF_DBI_BASE_ADDR_HI			0x354
> +#define PARF_SLV_ADDR_SPACE_SIZE		0x358
> +#define PARF_SLV_ADDR_SPACE_SIZE_HI		0x35c
> +#define PARF_ATU_BASE_ADDR			0x634
> +#define PARF_ATU_BASE_ADDR_HI			0x638
> +#define PARF_SRIS_MODE				0x644
> +#define PARF_DEVICE_TYPE			0x1000
> +#define PARF_BDF_TO_SID_CFG			0x2c00
> +
> +/* ELBI registers */
> +#define ELBI_SYS_STTS				0x08
> +
> +/* DBI registers */
> +#define DBI_CAP_ID_NXT_PTR			0x40
> +#define DBI_CON_STATUS				0x44
> +#define DBI_DEVICE_CAPABILITIES			0x74
> +#define DBI_LINK_CAPABILITIES			0x7c
> +#define DBI_LINK_CONTROL2_LINK_STATUS2		0xa0
> +#define DBI_L1SUB_CAPABILITY			0x234
> +#define DBI_ACK_F_ASPM_CTRL			0x70c
> +#define DBI_GEN3_RELATED_OFF			0x890
> +#define DBI_AUX_CLK_FREQ			0xb40
> +
> +#define DBI_L0S_ACCPT_LATENCY_MASK		GENMASK(8, 6)
> +#define DBI_L1_ACCPT_LATENCY_MASK		GENMASK(11, 9)
> +#define DBI_L0S_EXIT_LATENCY_MASK		GENMASK(14, 12)
> +#define DBI_L1_EXIT_LATENCY_MASK		GENMASK(17, 15)
> +#define DBI_ACK_N_FTS_MASK			GENMASK(15, 8)
> +
> +/* TCSR registers */
> +#define TCSR_PCIE_PERST_EN			0x258
> +#define TCSR_PERST_SEPARATION_ENABLE		0x270
> +
> +#define XMLH_LINK_UP				0x400
> +#define CORE_RESET_TIME_US_MIN			1000
> +#define CORE_RESET_TIME_US_MAX			1005
> +#define WAKE_DELAY_US				2000 /* 2 ms */
> +
> +#define to_pcie_ep(x)				dev_get_drvdata((x)->dev)

I don't think that this define adds some more readability or something else.

> +
> +enum qcom_pcie_ep_link_status {
> +	QCOM_PCIE_EP_LINK_DISABLED,
> +	QCOM_PCIE_EP_LINK_ENABLED,
> +	QCOM_PCIE_EP_LINK_UP,
> +	QCOM_PCIE_EP_LINK_DOWN,
> +};
> +
> +enum qcom_pcie_ep_irq {
> +	QCOM_PCIE_EP_INT_RESERVED,
> +	QCOM_PCIE_EP_INT_LINK_DOWN,
> +	QCOM_PCIE_EP_INT_BME,
> +	QCOM_PCIE_EP_INT_PM_TURNOFF,
> +	QCOM_PCIE_EP_INT_DEBUG,
> +	QCOM_PCIE_EP_INT_LTR,
> +	QCOM_PCIE_EP_INT_MHI_Q6,
> +	QCOM_PCIE_EP_INT_MHI_A7,
> +	QCOM_PCIE_EP_INT_DSTATE_CHANGE,
> +	QCOM_PCIE_EP_INT_L1SUB_TIMEOUT,
> +	QCOM_PCIE_EP_INT_MMIO_WRITE,
> +	QCOM_PCIE_EP_INT_CFG_WRITE,
> +	QCOM_PCIE_EP_INT_BRIDGE_FLUSH_N,
> +	QCOM_PCIE_EP_INT_LINK_UP,
> +	QCOM_PCIE_EP_INT_AER_LEGACY,
> +	QCOM_PCIE_EP_INT_PLS_ERR,
> +	QCOM_PCIE_EP_INT_PME_LEGACY,
> +	QCOM_PCIE_EP_INT_PLS_PME,
> +	QCOM_PCIE_EP_INT_MAX,
> +};
> +
> +static struct clk_bulk_data qcom_pcie_ep_clks[] = {
> +	{ .id = "cfg" },
> +	{ .id = "aux" },
> +	{ .id = "bus_master" },
> +	{ .id = "bus_slave" },
> +	{ .id = "ref" },
> +	{ .id = "sleep" },
> +	{ .id = "slave_q2a" },
> +};
> +
> +struct qcom_pcie_ep {
> +	struct dw_pcie pci;
> +
> +	void __iomem *parf;
> +	void __iomem *elbi;
> +	void __iomem *tcsr;
> +
> +	struct reset_control *core_reset;
> +	struct gpio_desc *reset;
> +	struct gpio_desc *wake;
> +	struct phy *phy;
> +
> +	resource_size_t dbi_phys;
> +	resource_size_t atu_phys;
> +
> +	enum qcom_pcie_ep_link_status link_status;
> +	int global_irq;
> +	int perst_irq;
> +};
> +
> +static void qcom_pcie_ep_enable_ltssm(struct qcom_pcie_ep *pcie_ep)
> +{
> +	u32 reg;
> +
> +	reg = readl(pcie_ep->parf + PARF_LTSSM);
> +	reg |= BIT(8);
> +	writel_relaxed(reg, pcie_ep->parf + PARF_LTSSM);
> +}
> +
> +static int qcom_pcie_ep_core_reset(struct qcom_pcie_ep *pcie_ep)
> +{
> +	struct dw_pcie *pci = &pcie_ep->pci;
> +	struct device *dev = pci->dev;
> +	int ret = 0;
> +
> +	ret = reset_control_assert(pcie_ep->core_reset);
> +	if (ret) {
> +		dev_err(dev, "Cannot assert core reset\n");
> +		return ret;
> +	}
> +
> +	usleep_range(CORE_RESET_TIME_US_MIN, CORE_RESET_TIME_US_MAX);
> +
> +	ret = reset_control_deassert(pcie_ep->core_reset);
> +	if (ret) {
> +		dev_err(dev, "Cannot de-assert core reset\n");
> +		return ret;
> +	}
> +
> +	usleep_range(CORE_RESET_TIME_US_MIN, CORE_RESET_TIME_US_MAX);
> +
> +	return 0;
> +}
> +
> +/*
> + * Delatch PERST_EN and PERST_SEPARATION_ENABLE with TCSR to avoid
> + * device reset during host reboot and hibernation. The driver is
> + * expected to handle this situation.
> + */
> +static void qcom_pcie_ep_configure_tcsr(struct qcom_pcie_ep *pcie_ep)
> +{
> +	writel_relaxed(0x0, pcie_ep->tcsr + TCSR_PCIE_PERST_EN);
> +	writel_relaxed(0x0, pcie_ep->tcsr + TCSR_PERST_SEPARATION_ENABLE);

Are you sure that _relaxed() variants (here and on the other places in
the driver) is enough? I'd use writel() for all places which are not
performance sesnsitive.

> +}
> +
> +static int qcom_pcie_ep_enable_resources(struct qcom_pcie_ep *pcie_ep)
> +{
> +	struct dw_pcie *pci = &pcie_ep->pci;
> +	struct device *dev = pci->dev;
> +	int ret;
> +
> +	ret = clk_bulk_prepare_enable(ARRAY_SIZE(qcom_pcie_ep_clks),
> +				      qcom_pcie_ep_clks);
> +	if (ret) {
> +		dev_err(dev, "Failed to enable clocks: %d\n", ret);

clk_bulk_prepare_enable already print errors so please drop this dev_err().

> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static void qcom_pcie_ep_disable_resources(struct qcom_pcie_ep *pcie_ep)
> +{
> +	clk_bulk_disable_unprepare(ARRAY_SIZE(qcom_pcie_ep_clks),
> +				   qcom_pcie_ep_clks);
> +}
> +
> +static void qcom_pcie_ep_configure_irq(struct qcom_pcie_ep *pcie_ep)
> +{
> +	u32 val;
> +
> +	writel_relaxed(0, pcie_ep->parf + PARF_INT_ALL_MASK);
> +	val = BIT(QCOM_PCIE_EP_INT_LINK_DOWN) |
> +		BIT(QCOM_PCIE_EP_INT_BME) |
> +		BIT(QCOM_PCIE_EP_INT_PM_TURNOFF) |
> +		BIT(QCOM_PCIE_EP_INT_DSTATE_CHANGE) |
> +		BIT(QCOM_PCIE_EP_INT_LINK_UP);
> +	writel_relaxed(val, pcie_ep->parf + PARF_INT_ALL_MASK);
> +}
> +
> +static int qcom_pcie_ep_core_init(struct qcom_pcie_ep *pcie_ep)
> +{
> +	struct dw_pcie *pci = &pcie_ep->pci;
> +	u32 val;
> +
> +	/* Disable BDF to SID mapping */
> +	val = readl_relaxed(pcie_ep->parf + PARF_BDF_TO_SID_CFG);
> +	val |= BIT(0);
> +	writel_relaxed(val, pcie_ep->parf + PARF_BDF_TO_SID_CFG);
> +
> +	/* enable debug IRQ */
> +	writel_relaxed((BIT(3) | BIT(2) | BIT(1)),
> +		       pcie_ep->parf + PARF_DEBUG_INT_EN);
> +
> +	/* Configure PCIe to endpoint mode */
> +	writel_relaxed(0x0, pcie_ep->parf + PARF_DEVICE_TYPE);
> +
> +	/* Configure PCIe core to support 1GB aperture */
> +	writel_relaxed(0x40000000, pcie_ep->parf + PARF_SLV_ADDR_SPACE_SIZE);
> +
> +	/* Allow entering L1 state */
> +	val = readl_relaxed(pcie_ep->parf + PARF_PM_CTRL);
> +	val &= ~BIT(5);
> +	writel_relaxed(val, pcie_ep->parf + PARF_PM_CTRL);
> +
> +	/* Configure Slave, DBI and iATU base addresses */
> +	writel_relaxed(BIT(0), pcie_ep->parf + PARF_SLV_ADDR_MSB_CTRL);
> +	writel_relaxed(0x200, pcie_ep->parf + PARF_SLV_ADDR_SPACE_SIZE_HI);
> +	writel_relaxed(0x0, pcie_ep->parf + PARF_SLV_ADDR_SPACE_SIZE);
> +	writel_relaxed(0x100, pcie_ep->parf + PARF_DBI_BASE_ADDR_HI);
> +	writel_relaxed(pcie_ep->dbi_phys, pcie_ep->parf + PARF_DBI_BASE_ADDR);
> +	writel_relaxed(0x100, pcie_ep->parf + PARF_ATU_BASE_ADDR_HI);
> +	writel_relaxed(pcie_ep->atu_phys, pcie_ep->parf + PARF_ATU_BASE_ADDR);
> +
> +	/* Read halts write */
> +	writel_relaxed(0x0, pcie_ep->parf + PARF_AXI_MSTR_RD_HALT_NO_WRITES);
> +	/* Write after write halt */
> +	writel_relaxed(BIT(31), pcie_ep->parf + PARF_AXI_MSTR_WR_ADDR_HALT);
> +	/* Q2A flush disable */
> +	writel_relaxed(0, pcie_ep->parf + PARF_Q2A_FLUSH);
> +
> +	/* Disable the DBI Wakeup */
> +	writel_relaxed(BIT(11), pcie_ep->parf + PARF_SYS_CTRL);
> +	/* Disable the debouncers */
> +	writel_relaxed(0x73, pcie_ep->parf + PARF_DB_CTRL);
> +	/* Disable core clock CGC */
> +	writel_relaxed(BIT(6), pcie_ep->parf + PARF_SYS_CTRL);
> +	/* Set AUX power to be on */
> +	writel_relaxed(BIT(4), pcie_ep->parf + PARF_SYS_CTRL);
> +	/* Request to exit from L1SS for MSI and LTR MSG */
> +	writel_relaxed(BIT(1), pcie_ep->parf + PARF_CFG_BITS);
> +
> +	dw_pcie_dbi_ro_wr_en(pci);
> +
> +	/* Set the PMC Register - to support PME in D0/D3hot/D3cold */
> +	val = dw_pcie_readl_dbi(pci, DBI_CAP_ID_NXT_PTR);
> +	val |= BIT(31) | BIT(30) | BIT(27);
> +	dw_pcie_writel_dbi(pci, DBI_CAP_ID_NXT_PTR, val);
> +
> +	/* Set the Endpoint L0s Acceptable Latency to 1us (max) */
> +	val = dw_pcie_readl_dbi(pci, DBI_DEVICE_CAPABILITIES);
> +	val |= FIELD_PREP(DBI_L0S_ACCPT_LATENCY_MASK, 0x7);
> +	dw_pcie_writel_dbi(pci, DBI_DEVICE_CAPABILITIES, val);
> +
> +	/* Set the Endpoint L1 Acceptable Latency to 1us (max) */
> +	val = dw_pcie_readl_dbi(pci, DBI_DEVICE_CAPABILITIES);
> +	val |= FIELD_PREP(DBI_L1_ACCPT_LATENCY_MASK, 0x7);
> +	dw_pcie_writel_dbi(pci, DBI_DEVICE_CAPABILITIES, val);
> +
> +	/* Set the L0s Exit Latency to 2us-4us = 0x6 */
> +	val = dw_pcie_readl_dbi(pci, DBI_LINK_CAPABILITIES);
> +	val |= FIELD_PREP(DBI_L0S_EXIT_LATENCY_MASK, 0x6);
> +	dw_pcie_writel_dbi(pci, DBI_LINK_CAPABILITIES, val);
> +
> +	/* Set the L1 Exit Latency to be 32us-64 us = 0x6 */
> +	val = dw_pcie_readl_dbi(pci, DBI_LINK_CAPABILITIES);
> +	val |= FIELD_PREP(DBI_L1_EXIT_LATENCY_MASK, 0x6);
> +	dw_pcie_writel_dbi(pci, DBI_LINK_CAPABILITIES, val);
> +
> +	/* L1ss is supported */
> +	val = dw_pcie_readl_dbi(pci, DBI_L1SUB_CAPABILITY);
> +	val |= 0x1f;
> +	dw_pcie_writel_dbi(pci, DBI_L1SUB_CAPABILITY, val);
> +
> +	/* Enable Clock Power Management */
> +	val = dw_pcie_readl_dbi(pci, DBI_LINK_CAPABILITIES);
> +	val |= BIT(18);
> +	dw_pcie_writel_dbi(pci, DBI_LINK_CAPABILITIES, val);
> +
> +	dw_pcie_dbi_ro_wr_dis(pci);
> +
> +	/* Set FTS value to match the PHY setting */
> +	val = dw_pcie_readl_dbi(pci, DBI_ACK_F_ASPM_CTRL);
> +	val |= FIELD_PREP(DBI_ACK_N_FTS_MASK, 0x80);
> +	dw_pcie_writel_dbi(pci, DBI_ACK_F_ASPM_CTRL, val);
> +
> +	dw_pcie_writel_dbi(pci, DBI_AUX_CLK_FREQ, 0x14);
> +
> +	/* Prevent L1ss wakeup after 100ms */
> +	val = dw_pcie_readl_dbi(pci, DBI_GEN3_RELATED_OFF);
> +	val &= ~BIT(0);
> +	dw_pcie_writel_dbi(pci, DBI_GEN3_RELATED_OFF, val);
> +
> +	/* Disable SRIS_MODE */
> +	val = readl_relaxed(pcie_ep->parf + PARF_SRIS_MODE);
> +	val &= ~BIT(0);
> +	writel_relaxed(val, pcie_ep->parf + PARF_SRIS_MODE);
> +
> +	qcom_pcie_ep_configure_irq(pcie_ep);
> +
> +	return 0;
> +}
> +
> +static int qcom_pcie_confirm_linkup(struct dw_pcie *pci)
> +{
> +	struct qcom_pcie_ep *pcie_ep = to_pcie_ep(pci);
> +	u32 reg;
> +
> +	reg = readl_relaxed(pcie_ep->elbi + ELBI_SYS_STTS);
> +
> +	return reg & XMLH_LINK_UP;
> +}
> +
> +static int qcom_pcie_start_link(struct dw_pcie *pci)
> +{
> +	struct qcom_pcie_ep *pcie_ep = to_pcie_ep(pci);
> +
> +	enable_irq(pcie_ep->perst_irq);
> +
> +	return 0;
> +}
> +
> +static int qcom_pcie_establish_link(struct dw_pcie *pci)
> +{
> +	struct qcom_pcie_ep *pcie_ep = to_pcie_ep(pci);
> +	struct device *dev = pci->dev;
> +	int ret;
> +
> +	if (pcie_ep->link_status == QCOM_PCIE_EP_LINK_ENABLED) {
> +		dev_info(dev, "Link is already enabled\n");
> +		return 0;
> +	}
> +
> +	/* Enable power and clocks */
> +	ret = qcom_pcie_ep_enable_resources(pcie_ep);
> +	if (ret) {
> +		dev_err(dev, "Failed to enable resources: %d\n", ret);
> +		return ret;
> +	}
> +
> +	/* Perform controller reset */
> +	ret = qcom_pcie_ep_core_reset(pcie_ep);
> +	if (ret) {
> +		dev_err(dev, "Failed to reset the core: %d\n", ret);
> +		goto err_disable_resources;
> +	}
> +
> +	/* Initialize PHY */
> +	ret = phy_init(pcie_ep->phy);
> +	if (ret) {
> +		dev_err(dev, "Failed to initialize PHY: %d\n", ret);
> +		goto err_disable_resources;
> +	}
> +
> +	/* Power ON PHY */
> +	ret = phy_power_on(pcie_ep->phy);
> +	if (ret) {
> +		dev_err(dev, "Failed to Power ON PHY: %d\n", ret);
> +		goto err_phy_exit;
> +	}
> +
> +	/* Assert WAKE# to RC to indicate device is ready */
> +	gpiod_set_value_cansleep(pcie_ep->wake, 0);
> +	usleep_range(WAKE_DELAY_US, WAKE_DELAY_US + 500);
> +	gpiod_set_value_cansleep(pcie_ep->wake, 1);
> +
> +	/* Configure TCSR */
> +	qcom_pcie_ep_configure_tcsr(pcie_ep);
> +
> +	/* Initialize the controller */
> +	ret = qcom_pcie_ep_core_init(pcie_ep);
> +	if (ret) {
> +		dev_err(dev, "Failed to init controller: %d\n", ret);
> +		goto err_phy_power_off;
> +	}
> +
> +	ret = dw_pcie_ep_init_complete(&pcie_ep->pci.ep);
> +	if (ret) {
> +		dev_err(dev, "Failed to complete initialization: %d\n", ret);
> +		goto err_phy_power_off;
> +	}
> +
> +	dw_pcie_ep_init_notify(&pcie_ep->pci.ep);
> +
> +	/* Enable LTSSM */
> +	qcom_pcie_ep_enable_ltssm(pcie_ep);
> +
> +	return 0;
> +/* TODO* assert reset? */
> +err_phy_power_off:
> +	phy_power_off(pcie_ep->phy);
> +err_phy_exit:
> +	phy_exit(pcie_ep->phy);
> +err_disable_resources:
> +	qcom_pcie_ep_disable_resources(pcie_ep);
> +
> +	return ret;
> +}
> +
> +static void qcom_pcie_disable_link(struct dw_pcie *pci)
> +{
> +	struct qcom_pcie_ep *pcie_ep = to_pcie_ep(pci);
> +	struct device *dev = pci->dev;
> +
> +	if (pcie_ep->link_status == QCOM_PCIE_EP_LINK_DISABLED) {
> +		dev_info(dev, "Link is already disabled\n");
> +		return;
> +	}
> +
> +	phy_power_off(pcie_ep->phy);
> +	phy_exit(pcie_ep->phy);
> +	qcom_pcie_ep_disable_resources(pcie_ep);
> +	pcie_ep->link_status = QCOM_PCIE_EP_LINK_DISABLED;
> +}
> +
> +/* Common DWC controller ops */
> +static const struct dw_pcie_ops pci_ops = {
> +	.link_up = qcom_pcie_confirm_linkup,
> +	.start_link = qcom_pcie_start_link,
> +	.stop_link = qcom_pcie_disable_link,
> +};
> +
> +static int qcom_pcie_ep_get_io_resources(struct platform_device *pdev,
> +					 struct qcom_pcie_ep *pcie_ep)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct dw_pcie *pci = &pcie_ep->pci;
> +	struct resource *res;
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "parf");
> +	pcie_ep->parf = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(pcie_ep->parf))
> +		return PTR_ERR(pcie_ep->parf);
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "dbi");
> +	pci->dbi_base = devm_pci_remap_cfg_resource(dev, res);
> +	if (IS_ERR(pci->dbi_base))
> +		return PTR_ERR(pci->dbi_base);
> +	pci->dbi_base2 = pci->dbi_base;
> +	pcie_ep->dbi_phys = res->start;
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "elbi");
> +	pcie_ep->elbi = devm_pci_remap_cfg_resource(dev, res);
> +	if (IS_ERR(pcie_ep->elbi))
> +		return PTR_ERR(pcie_ep->elbi);
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "atu");
> +	pci->atu_base = devm_pci_remap_cfg_resource(dev, res);
> +	if (IS_ERR(pci->atu_base))
> +		return PTR_ERR(pci->atu_base);
> +	pcie_ep->atu_phys = res->start;
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "tcsr");
> +	pcie_ep->tcsr = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(pcie_ep->tcsr))
> +		return PTR_ERR(pcie_ep->tcsr);
> +
> +	return 0;
> +}
> +
> +static int qcom_pcie_ep_get_resources(struct platform_device *pdev,
> +				      struct qcom_pcie_ep *pcie_ep)
> +{
> +	struct device *dev = &pdev->dev;
> +	int ret;
> +
> +	ret = qcom_pcie_ep_get_io_resources(pdev, pcie_ep);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to get io resources %d\n", ret);
> +		return ret;
> +	}
> +
> +	/* Enable GDSC power domain */
> +	ret = dev_pm_domain_attach(dev, true);
> +	if (ret)
> +		return ret;
> +
> +	ret = devm_clk_bulk_get(dev, ARRAY_SIZE(qcom_pcie_ep_clks),
> +				qcom_pcie_ep_clks);
> +	if (ret) {
> +		dev_err(dev, "Failed to get clocks: %d\n", ret);
> +		return ret;
> +	}
> +
> +	pcie_ep->core_reset = devm_reset_control_get_exclusive(dev, "core");
> +	if (IS_ERR(pcie_ep->core_reset))
> +		return PTR_ERR(pcie_ep->core_reset);
> +
> +	pcie_ep->reset = devm_gpiod_get(dev, "reset", GPIOD_IN);
> +	if (IS_ERR(pcie_ep->reset))
> +		return PTR_ERR(pcie_ep->reset);
> +
> +	pcie_ep->wake = devm_gpiod_get_optional(dev, "wake", GPIOD_OUT_HIGH);
> +	if (IS_ERR(pcie_ep->wake))
> +		return PTR_ERR(pcie_ep->wake);
> +
> +	pcie_ep->phy = devm_phy_optional_get(&pdev->dev, "pciephy");
> +	if (IS_ERR(pcie_ep->phy))
> +		ret = PTR_ERR(pcie_ep->phy);
> +
> +	return ret;
> +}
> +
> +/* TODO: Notify clients about PCIe state change */
> +static irqreturn_t qcom_pcie_ep_global_threaded_irq(int irq, void *data)
> +{
> +	struct qcom_pcie_ep *pcie_ep = data;
> +	struct dw_pcie *pci = &pcie_ep->pci;
> +	struct device *dev = pci->dev;
> +	u32 status = readl(pcie_ep->parf + PARF_INT_ALL_STATUS);
> +	u32 mask = readl(pcie_ep->parf + PARF_INT_ALL_MASK);
> +	u32 dstate, event, val;
> +
> +	writel_relaxed(status, pcie_ep->parf + PARF_INT_ALL_CLEAR);
> +	status &= mask;
> +
> +	for (event = 1; event < QCOM_PCIE_EP_INT_MAX; event++) {
> +		if (status & BIT(event)) {
> +			switch (event) {
> +			case QCOM_PCIE_EP_INT_LINK_DOWN:
> +				dev_info(dev, "Received Linkdown event\n");
> +				pcie_ep->link_status = QCOM_PCIE_EP_LINK_DOWN;
> +				break;
> +			case QCOM_PCIE_EP_INT_BME:
> +				dev_info(dev, "Received BME event. Link is enabled!\n");
> +				pcie_ep->link_status = QCOM_PCIE_EP_LINK_ENABLED;
> +				break;
> +			case QCOM_PCIE_EP_INT_PM_TURNOFF:
> +				dev_info(dev, "Received PM Turn-off event! Entering L23\n");
> +				val = readl_relaxed(pcie_ep->parf + PARF_PM_CTRL);
> +				val |= BIT(2);
> +				writel_relaxed(val, pcie_ep->parf + PARF_PM_CTRL);
> +				break;
> +			case QCOM_PCIE_EP_INT_DSTATE_CHANGE:
> +				dstate = dw_pcie_readl_dbi(pci, DBI_CON_STATUS) & 0x3;
> +				dev_info(dev, "Received D%d state event\n", dstate);
> +				if (dstate == 3) {
> +					val = readl_relaxed(pcie_ep->parf + PARF_PM_CTRL);
> +					val |= BIT(1);
> +					writel_relaxed(val, pcie_ep->parf + PARF_PM_CTRL);
> +				}
> +				/* Handle D0 state change */

I don't understand this comment.

> +				break;
> +			case QCOM_PCIE_EP_INT_LINK_UP:
> +				dev_info(dev, "Received Linkup event. Enumeration complete!\n");
> +				dw_pcie_ep_linkup(&pci->ep);
> +				pcie_ep->link_status = QCOM_PCIE_EP_LINK_UP;
> +				break;
> +			default:
> +				dev_err(dev, "Received unknown event: %d\n", event);

Are you sure that you want those dev_info() and dev_err() in irq
hanldler even when it is threaded? I'd drop all dev_info|err() or make
them dev_dbg() if they can help.

> +				break;
> +			}
> +		}
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t qcom_pcie_ep_perst_threaded_irq(int irq, void *data)
> +{
> +	struct qcom_pcie_ep *pcie_ep = data;
> +	struct dw_pcie *pci = &pcie_ep->pci;
> +	struct device *dev = pci->dev;
> +	u32 perst;
> +
> +	perst = gpiod_get_value(pcie_ep->reset);
> +
> +	if (perst) {
> +		/* Start link training */
> +		dev_info(dev, "PERST de-asserted by host. Starting link training!\n");
> +		qcom_pcie_establish_link(pci);
> +	} else {
> +		/* Shutdown the link if the link is already on */
> +		dev_info(dev, "PERST asserted by host. Shutting down the PCIe link!\n");

Those prints sounds like a candidate for dev_dbg or even you can drop them.

> +		qcom_pcie_disable_link(pci);
> +	}
> +
> +	/* Set trigger type based on the next expected value of perst gpio */

IMO commenting obvious code is not good practice.

> +	irq_set_irq_type(gpiod_to_irq(pcie_ep->reset),
> +			 (perst ? IRQF_TRIGGER_LOW : IRQF_TRIGGER_HIGH));
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int qcom_pcie_ep_enable_irq_resources(struct platform_device *pdev,
> +					     struct qcom_pcie_ep *pcie_ep)
> +{
> +	int irq, ret;
> +
> +	irq = platform_get_irq_byname(pdev, "global");
> +	if (irq < 0) {
> +		dev_err(&pdev->dev, "Failed to get Global IRQ\n");
> +		return irq;
> +	}
> +
> +	ret = devm_request_threaded_irq(&pdev->dev, irq, NULL,
> +					qcom_pcie_ep_global_threaded_irq,
> +					IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
> +					"global_irq", pcie_ep);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to request Global IRQ\n");
> +		return ret;
> +	}
> +
> +	pcie_ep->perst_irq = gpiod_to_irq(pcie_ep->reset);
> +	irq_set_status_flags(pcie_ep->perst_irq, IRQ_NOAUTOEN);
> +	ret = devm_request_threaded_irq(&pdev->dev, pcie_ep->perst_irq, NULL,
> +					qcom_pcie_ep_perst_threaded_irq,
> +					IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
> +					"perst_irq", pcie_ep);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to request PERST IRQ\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int qcom_pcie_ep_raise_irq(struct dw_pcie_ep *ep, u8 func_no,
> +				  enum pci_epc_irq_type type, u16 interrupt_num)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> +
> +	switch (type) {
> +	case PCI_EPC_IRQ_LEGACY:
> +		return dw_pcie_ep_raise_legacy_irq(ep, func_no);
> +	case PCI_EPC_IRQ_MSI:
> +		return dw_pcie_ep_raise_msi_irq(ep, func_no, interrupt_num);
> +	default:
> +		dev_err(pci->dev, "Unknown IRQ type\n");
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct pci_epc_features qcom_pcie_epc_features = {
> +	.linkup_notifier = true,
> +	.core_init_notifier = true,
> +	.msi_capable = true,
> +	.msix_capable = false,
> +};
> +
> +static const struct pci_epc_features *
> +qcom_pcie_epc_get_features(struct dw_pcie_ep *pci_ep)
> +{
> +	return &qcom_pcie_epc_features;
> +}
> +
> +static void qcom_pcie_ep_init(struct dw_pcie_ep *ep)
> +{
> +	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> +	enum pci_barno bar;
> +
> +	for (bar = BAR_0; bar <= BAR_5; bar++)
> +		dw_pcie_ep_reset_bar(pci, bar);
> +}
> +
> +static struct dw_pcie_ep_ops pci_ep_ops = {
> +	.ep_init = qcom_pcie_ep_init,
> +	.raise_irq = qcom_pcie_ep_raise_irq,
> +	.get_features = qcom_pcie_epc_get_features,
> +};
> +
> +static const struct of_device_id qcom_pcie_ep_match[] = {
> +	{ .compatible = "qcom,sdx55-pcie-ep", },
> +	{ }
> +};
> +
> +static int qcom_pcie_ep_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct qcom_pcie_ep *pcie_ep;
> +	int ret;
> +
> +	pcie_ep = devm_kzalloc(dev, sizeof(*pcie_ep), GFP_KERNEL);
> +	if (!pcie_ep)
> +		return -ENOMEM;
> +
> +	pcie_ep->pci.dev = dev;
> +	pcie_ep->pci.ops = &pci_ops;
> +	pcie_ep->pci.ep.ops = &pci_ep_ops;
> +
> +	ret = qcom_pcie_ep_get_resources(pdev, pcie_ep);
> +	if (ret) {
> +		dev_err(dev, "Failed to get resources:%d\n", ret);
> +		return ret;
> +	}
> +
> +	/* Enable power and clocks */

Useless comment.

> +	ret = qcom_pcie_ep_enable_resources(pcie_ep);
> +	if (ret) {
> +		dev_err(dev, "Failed to enable resources: %d\n", ret);
> +		return ret;
> +	}
> +
> +	/* Perform controller reset */

ditto

> +	ret = qcom_pcie_ep_core_reset(pcie_ep);
> +	if (ret) {
> +		dev_err(dev, "Failed to reset the core: %d\n", ret);

qcom_pcie_ep_core_reset() already print errors

> +		goto err_disable_resources;
> +	}
> +
> +	/* Initialize PHY */

ditto

> +	ret = phy_init(pcie_ep->phy);
> +	if (ret) {
> +		dev_err(dev, "Failed to initialize PHY: %d\n", ret);

phy_init() already print an error.

> +		goto err_disable_resources;
> +	}
> +
> +	/* PHY needs to be powered on for dw_pcie_ep_init() */

useless comment.

> +	ret = phy_power_on(pcie_ep->phy);
> +	if (ret) {
> +		dev_err(dev, "Failed to Power ON PHY: %d\n", ret);

phy_power_on already has prints in case of an error

> +		goto err_phy_exit;
> +	}
> +
> +	platform_set_drvdata(pdev, pcie_ep);
> +
> +	ret = qcom_pcie_ep_enable_irq_resources(pdev, pcie_ep);
> +	if (ret) {
> +		dev_err(dev, "Failed to get IRQ resources %d\n", ret);

errors are printed already form qcom_pcie_ep_enable_irq_resources()

> +		goto err_phy_power_off;
> +	}
> +
> +	ret = dw_pcie_ep_init(&pcie_ep->pci.ep);
> +	if (ret) {
> +		dev_err(dev, "Failed to initialize endpoint:%d\n", ret);

I think this dev_err() should be dropped.

Please revisit all those dev_err and dev_info in the driver and if
possible reduce thei

> +		goto err_phy_power_off;
> +	}
> +
> +	return 0;
> +
> +err_phy_power_off:
> +	phy_power_off(pcie_ep->phy);
> +err_phy_exit:
> +	phy_exit(pcie_ep->phy);
> +err_disable_resources:
> +	qcom_pcie_ep_disable_resources(pcie_ep);
> +
> +	return ret;
> +}
> +
> +static struct platform_driver qcom_pcie_ep_driver = {
> +	.probe	= qcom_pcie_ep_probe,
> +	.driver	= {
> +		.name		= "qcom-pcie-ep",
> +		.suppress_bind_attrs = true,
> +		.of_match_table	= qcom_pcie_ep_match,
> +	},
> +};
> +builtin_platform_driver(qcom_pcie_ep_driver);
> +
> +MODULE_AUTHOR("Siddartha Mohanadoss <smohanad@codeaurora.org>");
> +MODULE_AUTHOR("Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>");
> +MODULE_DESCRIPTION("Qualcomm PCIe Endpoint controller driver");
> +MODULE_LICENSE("GPL v2");
> 

-- 
regards,
Stan