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Message-ID: <2432dafc-4101-4b23-90b2-85ea5459435c@linux.dev>
Date: Tue, 13 Jan 2026 10:26:04 -0500
From: Sean Anderson <sean.anderson@...ux.dev>
To: manivannan.sadhasivam@....qualcomm.com, Rob Herring <robh@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jirislaby@...nel.org>, Nathan Chancellor <nathan@...nel.org>,
Nicolas Schier <nicolas.schier@...ux.dev>, Hans de Goede <hansg@...nel.org>,
Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
Mark Pearson <mpearson-lenovo@...ebb.ca>,
"Derek J. Clark" <derekjohn.clark@...il.com>,
Manivannan Sadhasivam <mani@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
<conor+dt@...nel.org>, Marcel Holtmann <marcel@...tmann.org>,
Luiz Augusto von Dentz <luiz.dentz@...il.com>,
Bartosz Golaszewski <brgl@...ev.pl>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Bartosz Golaszewski <brgl@...nel.org>
Cc: linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-kbuild@...r.kernel.org, platform-driver-x86@...r.kernel.org,
linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
linux-arm-msm@...r.kernel.org, linux-bluetooth@...r.kernel.org,
linux-pm@...r.kernel.org, Stephan Gerhold <stephan.gerhold@...aro.org>,
Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
linux-acpi@...r.kernel.org
Subject: Re: [PATCH v4 8/9] power: sequencing: pcie-m2: Add support for PCIe
M.2 Key E connectors
On 1/12/26 11:26, Manivannan Sadhasivam via B4 Relay wrote:
> From: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
>
> Add support for handling the power sequence of the PCIe M.2 Key E
> connectors. These connectors are used to attach the Wireless Connectivity
> devices to the host machine including combinations of WiFi, BT, NFC using
> interfaces such as PCIe/SDIO for WiFi, USB/UART for BT and I2C for NFC.
>
> Currently, this driver supports only the PCIe interface for WiFi and UART
> interface for BT. The driver also only supports driving the 3.3v/1.8v power
> supplies and W_DISABLE{1/2}# GPIOs. The optional signals of the Key E
> connectors are not currently supported.
>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> ---
> drivers/power/sequencing/Kconfig | 1 +
> drivers/power/sequencing/pwrseq-pcie-m2.c | 110 ++++++++++++++++++++++++++++--
> 2 files changed, 104 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/power/sequencing/Kconfig b/drivers/power/sequencing/Kconfig
> index f5fff84566ba..29bd204319cc 100644
> --- a/drivers/power/sequencing/Kconfig
> +++ b/drivers/power/sequencing/Kconfig
> @@ -38,6 +38,7 @@ config POWER_SEQUENCING_TH1520_GPU
> config POWER_SEQUENCING_PCIE_M2
> tristate "PCIe M.2 connector power sequencing driver"
> depends on OF || COMPILE_TEST
> + depends on PCI
> help
> Say Y here to enable the power sequencing driver for PCIe M.2
> connectors. This driver handles the power sequencing for the M.2
> diff --git a/drivers/power/sequencing/pwrseq-pcie-m2.c b/drivers/power/sequencing/pwrseq-pcie-m2.c
> index e01e19123415..4b85a40d7692 100644
> --- a/drivers/power/sequencing/pwrseq-pcie-m2.c
> +++ b/drivers/power/sequencing/pwrseq-pcie-m2.c
> @@ -4,12 +4,16 @@
> * Author: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> */
>
> +#include <linux/err.h>
> #include <linux/device.h>
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> #include <linux/mod_devicetable.h>
> #include <linux/module.h>
> #include <linux/of.h>
> #include <linux/of_graph.h>
> #include <linux/of_platform.h>
> +#include <linux/pci.h>
> #include <linux/platform_device.h>
> #include <linux/pwrseq/provider.h>
> #include <linux/regulator/consumer.h>
> @@ -25,17 +29,19 @@ struct pwrseq_pcie_m2_ctx {
> const struct pwrseq_pcie_m2_pdata *pdata;
> struct regulator_bulk_data *regs;
> size_t num_vregs;
> - struct notifier_block nb;
> + struct gpio_desc *w_disable1_gpio;
> + struct gpio_desc *w_disable2_gpio;
> + struct device *dev;
> };
>
> -static int pwrseq_pcie_m2_m_vregs_enable(struct pwrseq_device *pwrseq)
> +static int pwrseq_pcie_m2_vregs_enable(struct pwrseq_device *pwrseq)
> {
> struct pwrseq_pcie_m2_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
>
> return regulator_bulk_enable(ctx->num_vregs, ctx->regs);
> }
>
> -static int pwrseq_pcie_m2_m_vregs_disable(struct pwrseq_device *pwrseq)
> +static int pwrseq_pcie_m2_vregs_disable(struct pwrseq_device *pwrseq)
> {
> struct pwrseq_pcie_m2_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
>
> @@ -44,18 +50,84 @@ static int pwrseq_pcie_m2_m_vregs_disable(struct pwrseq_device *pwrseq)
>
> static const struct pwrseq_unit_data pwrseq_pcie_m2_vregs_unit_data = {
> .name = "regulators-enable",
> - .enable = pwrseq_pcie_m2_m_vregs_enable,
> - .disable = pwrseq_pcie_m2_m_vregs_disable,
> + .enable = pwrseq_pcie_m2_vregs_enable,
> + .disable = pwrseq_pcie_m2_vregs_disable,
> };
>
> -static const struct pwrseq_unit_data *pwrseq_pcie_m2_m_unit_deps[] = {
> +static const struct pwrseq_unit_data *pwrseq_pcie_m2_unit_deps[] = {
> &pwrseq_pcie_m2_vregs_unit_data,
> NULL
> };
>
> +static int pwrseq_pci_m2_e_uart_enable(struct pwrseq_device *pwrseq)
> +{
> + struct pwrseq_pcie_m2_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
> +
> + return gpiod_set_value_cansleep(ctx->w_disable2_gpio, 0);
> +}
> +
> +static int pwrseq_pci_m2_e_uart_disable(struct pwrseq_device *pwrseq)
> +{
> + struct pwrseq_pcie_m2_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
> +
> + return gpiod_set_value_cansleep(ctx->w_disable2_gpio, 1);
> +}
> +
> +static const struct pwrseq_unit_data pwrseq_pcie_m2_e_uart_unit_data = {
> + .name = "uart-enable",
> + .deps = pwrseq_pcie_m2_unit_deps,
> + .enable = pwrseq_pci_m2_e_uart_enable,
> + .disable = pwrseq_pci_m2_e_uart_disable,
> +};
> +
> +static int pwrseq_pci_m2_e_pcie_enable(struct pwrseq_device *pwrseq)
> +{
> + struct pwrseq_pcie_m2_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
> +
> + return gpiod_set_value_cansleep(ctx->w_disable1_gpio, 0);
> +}
> +
> +static int pwrseq_pci_m2_e_pcie_disable(struct pwrseq_device *pwrseq)
> +{
> + struct pwrseq_pcie_m2_ctx *ctx = pwrseq_device_get_drvdata(pwrseq);
> +
> + return gpiod_set_value_cansleep(ctx->w_disable1_gpio, 1);
> +}
> +
> +static const struct pwrseq_unit_data pwrseq_pcie_m2_e_pcie_unit_data = {
> + .name = "pcie-enable",
> + .deps = pwrseq_pcie_m2_unit_deps,
> + .enable = pwrseq_pci_m2_e_pcie_enable,
> + .disable = pwrseq_pci_m2_e_pcie_disable,
> +};
> +
> static const struct pwrseq_unit_data pwrseq_pcie_m2_m_pcie_unit_data = {
> .name = "pcie-enable",
> - .deps = pwrseq_pcie_m2_m_unit_deps,
> + .deps = pwrseq_pcie_m2_unit_deps,
> +};
> +
> +static int pwrseq_pcie_m2_e_pwup_delay(struct pwrseq_device *pwrseq)
> +{
> + /*
> + * FIXME: This delay is only required for some Qcom WLAN/BT cards like
> + * WCN7850 and not for all devices. But currently, there is no way to
> + * identify the device model before enumeration.
> + */
> + msleep(50);
Section 3.1.4 of the M.2 spec says that "Power Valid to PERST# input
inactive" (T_PVPGL) is "Implementation specific recommended 50 ms." So I
think we should delay for at least 50 ms for all M.2 cards.
Additionally, the PCIe CEM specifies that "Power stable to PERST#
inactive" (T_PVPERL) must be at least 100 ms. So I think we should just
delay for 100 ms regardless of the slot, perhaps making this
configurable in the devicetree if e.g. the system integrator knows the
soldered-down M.2 requires less initialization time. This is exactly
what I proposed in [1].
--Sean
[1] https://lore.kernel.org/linux-pci/20251219172222.2808195-2-sean.anderson@linux.dev/
> + return 0;
> +}
> +
> +static const struct pwrseq_target_data pwrseq_pcie_m2_e_uart_target_data = {
> + .name = "uart",
> + .unit = &pwrseq_pcie_m2_e_uart_unit_data,
> + .post_enable = pwrseq_pcie_m2_e_pwup_delay,
> +};
> +
> +static const struct pwrseq_target_data pwrseq_pcie_m2_e_pcie_target_data = {
> + .name = "pcie",
> + .unit = &pwrseq_pcie_m2_e_pcie_unit_data,
> + .post_enable = pwrseq_pcie_m2_e_pwup_delay,
> };
>
> static const struct pwrseq_target_data pwrseq_pcie_m2_m_pcie_target_data = {
> @@ -63,11 +135,21 @@ static const struct pwrseq_target_data pwrseq_pcie_m2_m_pcie_target_data = {
> .unit = &pwrseq_pcie_m2_m_pcie_unit_data,
> };
>
> +static const struct pwrseq_target_data *pwrseq_pcie_m2_e_targets[] = {
> + &pwrseq_pcie_m2_e_pcie_target_data,
> + &pwrseq_pcie_m2_e_uart_target_data,
> + NULL
> +};
> +
> static const struct pwrseq_target_data *pwrseq_pcie_m2_m_targets[] = {
> &pwrseq_pcie_m2_m_pcie_target_data,
> NULL
> };
>
> +static const struct pwrseq_pcie_m2_pdata pwrseq_pcie_m2_e_of_data = {
> + .targets = pwrseq_pcie_m2_e_targets,
> +};
> +
> static const struct pwrseq_pcie_m2_pdata pwrseq_pcie_m2_m_of_data = {
> .targets = pwrseq_pcie_m2_m_targets,
> };
> @@ -126,6 +208,16 @@ static int pwrseq_pcie_m2_probe(struct platform_device *pdev)
> return dev_err_probe(dev, ret,
> "Failed to get all regulators\n");
>
> + ctx->w_disable1_gpio = devm_gpiod_get_optional(dev, "w-disable1", GPIOD_OUT_HIGH);
> + if (IS_ERR(ctx->w_disable1_gpio))
> + return dev_err_probe(dev, PTR_ERR(ctx->w_disable1_gpio),
> + "Failed to get the W_DISABLE_1# GPIO\n");
> +
> + ctx->w_disable2_gpio = devm_gpiod_get_optional(dev, "w-disable2", GPIOD_OUT_HIGH);
> + if (IS_ERR(ctx->w_disable2_gpio))
> + return dev_err_probe(dev, PTR_ERR(ctx->w_disable2_gpio),
> + "Failed to get the W_DISABLE_2# GPIO\n");
> +
> ctx->num_vregs = ret;
>
> ret = devm_add_action_or_reset(dev, pwrseq_pcie_free_resources, ctx);
> @@ -151,6 +243,10 @@ static const struct of_device_id pwrseq_pcie_m2_of_match[] = {
> .compatible = "pcie-m2-m-connector",
> .data = &pwrseq_pcie_m2_m_of_data,
> },
> + {
> + .compatible = "pcie-m2-e-connector",
> + .data = &pwrseq_pcie_m2_e_of_data,
> + },
> { }
> };
> MODULE_DEVICE_TABLE(of, pwrseq_pcie_m2_of_match);
>
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