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Message-ID: <ntlgplc5pvps65c3szss5ozbnfgvq4rnk74yfeoxurinx6udho@z6crcjxmv7nh>
Date: Tue, 15 Jul 2025 15:33:38 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Komal Bajaj <komal.bajaj@....qualcomm.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Souradeep Chowdhury <quic_schowdhu@...cinc.com>,
linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-msm@...r.kernel.org,
Melody Olvera <quic_molvera@...cinc.com>,
Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH v5] usb: misc: qcom_eud: Access EUD_MODE_MANAGER2 through
secure calls
On Tue, Jul 15, 2025 at 05:15:27PM +0530, Komal Bajaj wrote:
> EUD_MODE_MANAGER2 register is mapped to a memory region that is marked
> as read-only for HLOS, enforcing access restrictions that prohibit
> direct memory-mapped writes via writel().
>
> Attempts to write to this region from HLOS can result in silent failures
> or memory access violations, particularly when toggling EUD (Embedded
> USB Debugger) state. To ensure secure register access, modify the driver
> to use qcom_scm_io_writel(), which routes the write operation to Qualcomm
> Secure Channel Monitor (SCM). SCM has the necessary permissions to access
> protected memory regions, enabling reliable control over EUD state.
>
> SC7280, the only user of EUD is also affected, indicating that this could
> never have worked on a properly fused device.
>
> Fixes: 9a1bf58ccd44 ("usb: misc: eud: Add driver support for Embedded USB Debugger(EUD)")
> Signed-off-by: Melody Olvera <quic_molvera@...cinc.com>
> Signed-off-by: Komal Bajaj <komal.bajaj@....qualcomm.com>
> Reviewed-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> ---
> Changes in v5:
> * Changed select QCOM_SCM to depends on QCOM_SCM in Kconfig per Greg's review
> * Link to v4: https://lore.kernel.org/all/20250709065533.25724-1-komal.bajaj@oss.qualcomm.com/
>
> Changes in v4:
> * Added error logging in disable_eud() for SCM write failures, per Konrad’s suggestion
> * Link to v3: https://lore.kernel.org/all/20250708085208.19089-1-komal.bajaj@oss.qualcomm.com/
>
> Changes in v3:
> * Moved secure write before normal writes
> * Added error checking in disable_eud()
> * Use ENOMEM error code if platform_get_resource() fails
> * Select QCOM_SCM driver if USB_QCOM_EUD is enabled
> * Link to v2: https://lore.kernel.org/all/20250627125131.27606-1-komal.bajaj@oss.qualcomm.com/
>
> Changes in v2:
> * Drop separate compatible to be added for secure eud
> * Use secure call to access EUD mode manager register
> * Link to v1: https://lore.kernel.org/all/20240807183205.803847-1-quic_molvera@quicinc.com/
> ---
> drivers/usb/misc/Kconfig | 1 +
> drivers/usb/misc/qcom_eud.c | 27 +++++++++++++++++++++------
> 2 files changed, 22 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig
> index 6497c4e81e951a14201ad965dadc29f9888f8254..73ebd3257625e4567f33636cdfd756344b9ed4e7 100644
> --- a/drivers/usb/misc/Kconfig
> +++ b/drivers/usb/misc/Kconfig
> @@ -147,6 +147,7 @@ config USB_APPLEDISPLAY
> config USB_QCOM_EUD
> tristate "QCOM Embedded USB Debugger(EUD) Driver"
> depends on ARCH_QCOM || COMPILE_TEST
> + depends on QCOM_SCM
> select USB_ROLE_SWITCH
> help
> This module enables support for Qualcomm Technologies, Inc.
> diff --git a/drivers/usb/misc/qcom_eud.c b/drivers/usb/misc/qcom_eud.c
> index 83079c414b4f281b2136d0d1eb39418c7f94ff8c..a58081f53db32935f09c685e4599985285133891 100644
> --- a/drivers/usb/misc/qcom_eud.c
> +++ b/drivers/usb/misc/qcom_eud.c
> @@ -15,6 +15,7 @@
> #include <linux/slab.h>
> #include <linux/sysfs.h>
> #include <linux/usb/role.h>
> +#include <linux/firmware/qcom/qcom_scm.h>
>
> #define EUD_REG_INT1_EN_MASK 0x0024
> #define EUD_REG_INT_STATUS_1 0x0044
> @@ -34,7 +35,7 @@ struct eud_chip {
> struct device *dev;
> struct usb_role_switch *role_sw;
> void __iomem *base;
> - void __iomem *mode_mgr;
> + phys_addr_t mode_mgr;
> unsigned int int_status;
> int irq;
> bool enabled;
> @@ -43,18 +44,30 @@ struct eud_chip {
>
> static int enable_eud(struct eud_chip *priv)
> {
> + int ret;
> +
> + ret = qcom_scm_io_writel(priv->mode_mgr + EUD_REG_EUD_EN2, 1);
> + if (ret)
> + return ret;
> +
> writel(EUD_ENABLE, priv->base + EUD_REG_CSR_EUD_EN);
> writel(EUD_INT_VBUS | EUD_INT_SAFE_MODE,
> priv->base + EUD_REG_INT1_EN_MASK);
> - writel(1, priv->mode_mgr + EUD_REG_EUD_EN2);
>
> return usb_role_switch_set_role(priv->role_sw, USB_ROLE_DEVICE);
> }
>
> static void disable_eud(struct eud_chip *priv)
> {
> + int ret;
> +
> + ret = qcom_scm_io_writel(priv->mode_mgr + EUD_REG_EUD_EN2, 0);
> + if (ret) {
> + dev_err(priv->dev, "failed to disable eud\n");
> + return;
Change this (and enable_store()) to propagate the error code.
> + }
> +
> writel(0, priv->base + EUD_REG_CSR_EUD_EN);
> - writel(0, priv->mode_mgr + EUD_REG_EUD_EN2);
> }
>
> static ssize_t enable_show(struct device *dev,
> @@ -178,6 +191,7 @@ static void eud_role_switch_release(void *data)
> static int eud_probe(struct platform_device *pdev)
> {
> struct eud_chip *chip;
> + struct resource *res;
> int ret;
>
> chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
> @@ -200,9 +214,10 @@ static int eud_probe(struct platform_device *pdev)
> if (IS_ERR(chip->base))
> return PTR_ERR(chip->base);
>
> - chip->mode_mgr = devm_platform_ioremap_resource(pdev, 1);
> - if (IS_ERR(chip->mode_mgr))
> - return PTR_ERR(chip->mode_mgr);
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> + if (!res)
> + return -ENODEV;
> + chip->mode_mgr = res->start;
>
> chip->irq = platform_get_irq(pdev, 0);
> if (chip->irq < 0)
>
> ---
> base-commit: 347e9f5043c89695b01e66b3ed111755afcf1911
> change-id: 20250715-eud_mode_manager_secure_access-6e57e3c71ec2
>
> Best regards,
> --
> Komal Bajaj <komal.bajaj@....qualcomm.com>
>
--
With best wishes
Dmitry
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