[RFC][PATCH 0/5] Allow for qcom-pdc, pinctrl-msm and qcom-scm drivers to be loadable as modules

[RFC][PATCH 0/5] Allow for qcom-pdc, pinctrl-msm and qcom-scm drivers to be loadable as modules

[John Stultz]

This patch series provides exports and config tweaks to allow
the qcom-pdc, pinctrl-msm and qcom-scm drivers to be able to be
configured as permement modules (particularlly useful for the
Android Generic Kernel Image efforts).

Feedback would be appreciated!

thanks
-john

Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-arm-msm@vger.kernel.org
Cc: iommu@lists.linux-foundation.org
Cc: linux-gpio@vger.kernel.org

John Stultz (5):
  irq: irqdomain: Export irq_domain_update_bus_token
  irq: irqchip: Export irq_chip_retrigger_hierarchy and
    irq_chip_set_vcpu_affinity_parent
  irqchip: Allow QCOM_PDC to be loadable as a perment module
  pinctrl: qcom: Allow pinctrl-msm code to be loadable as a module
  firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a
    permenent module

 drivers/firmware/Kconfig           |  2 +-
 drivers/firmware/Makefile          |  3 ++-
 drivers/firmware/qcom_scm.c        |  4 ++++
 drivers/iommu/Kconfig              |  2 ++
 drivers/irqchip/Kconfig            |  2 +-
 drivers/irqchip/qcom-pdc.c         | 30 ++++++++++++++++++++++++++++++
 drivers/pinctrl/qcom/Kconfig       |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm.c |  3 +++
 kernel/irq/chip.c                  |  3 ++-
 kernel/irq/irqdomain.c             |  1 +
 10 files changed, 47 insertions(+), 5 deletions(-)

-- 
2.17.1

[RFC][PATCH 1/5] irq: irqdomain: Export irq_domain_update_bus_token

[John Stultz]

Add export for irq_domain_update_bus_token() so that
we can allow drivers like the qcom-pdc driver to be
loadable as a module.

Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-arm-msm@vger.kernel.org
Cc: iommu@lists.linux-foundation.org
Cc: linux-gpio@vger.kernel.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 kernel/irq/irqdomain.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index a4c2c915511d..ca974d965fda 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -281,6 +281,7 @@ void irq_domain_update_bus_token(struct irq_domain *domain,
 
 	mutex_unlock(&irq_domain_mutex);
 }
+EXPORT_SYMBOL_GPL(irq_domain_update_bus_token);
 
 /**
  * irq_domain_add_simple() - Register an irq_domain and optionally map a range of irqs
-- 
2.17.1

[RFC][PATCH 2/5] irq: irqchip: Export irq_chip_retrigger_hierarchy and irq_chip_set_vcpu_affinity_parent

[John Stultz]

Add EXPORT_SYMBOL_GPL entries for irq_chip_retrigger_hierarchy()
and irq_chip_set_vcpu_affinity_parent() so that we can allow
drivers like the qcom-pdc driver to be loadable as a module.

Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-arm-msm@vger.kernel.org
Cc: iommu@lists.linux-foundation.org
Cc: linux-gpio@vger.kernel.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 kernel/irq/chip.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 41e7e37a0928..ba6ce66d7ed6 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -1478,6 +1478,7 @@ int irq_chip_retrigger_hierarchy(struct irq_data *data)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(irq_chip_retrigger_hierarchy);
 
 /**
  * irq_chip_set_vcpu_affinity_parent - Set vcpu affinity on the parent interrupt
@@ -1492,7 +1493,7 @@ int irq_chip_set_vcpu_affinity_parent(struct irq_data *data, void *vcpu_info)
 
 	return -ENOSYS;
 }
-
+EXPORT_SYMBOL_GPL(irq_chip_set_vcpu_affinity_parent);
 /**
  * irq_chip_set_wake_parent - Set/reset wake-up on the parent interrupt
  * @data:	Pointer to interrupt specific data
-- 
2.17.1

[RFC][PATCH 3/5] irqchip: Allow QCOM_PDC to be loadable as a perment module

[John Stultz]

Allows qcom-pdc driver to be loaded as a permenent module

Also, due to the fact that IRQCHIP_DECLARE becomes a no-op when
building as a module, we have to add the platform driver hooks
explicitly.

Thanks to Saravana for his help on pointing out the
IRQCHIP_DECLARE issue and guidance on a solution.

Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-arm-msm@vger.kernel.org
Cc: iommu@lists.linux-foundation.org
Cc: linux-gpio@vger.kernel.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 drivers/irqchip/Kconfig    |  2 +-
 drivers/irqchip/qcom-pdc.c | 30 ++++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index 29fead208cad..12765bed08f9 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -425,7 +425,7 @@ config GOLDFISH_PIC
          for Goldfish based virtual platforms.
 
 config QCOM_PDC
-	bool "QCOM PDC"
+	tristate "QCOM PDC"
 	depends on ARCH_QCOM
 	select IRQ_DOMAIN_HIERARCHY
 	help
diff --git a/drivers/irqchip/qcom-pdc.c b/drivers/irqchip/qcom-pdc.c
index 6ae9e1f0819d..98d74160afcd 100644
--- a/drivers/irqchip/qcom-pdc.c
+++ b/drivers/irqchip/qcom-pdc.c
@@ -11,7 +11,9 @@
 #include <linux/irqdomain.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_irq.h>
 #include <linux/of_address.h>
 #include <linux/of_device.h>
 #include <linux/soc/qcom/irq.h>
@@ -430,4 +432,32 @@ static int qcom_pdc_init(struct device_node *node, struct device_node *parent)
 	return ret;
 }
 
+#ifdef MODULE
+static int qcom_pdc_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct device_node *parent = of_irq_find_parent(np);
+
+	return qcom_pdc_init(np, parent);
+}
+
+static const struct of_device_id qcom_pdc_match_table[] = {
+	{ .compatible = "qcom,pdc" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, qcom_pdc_match_table);
+
+static struct platform_driver qcom_pdc_driver = {
+	.probe = qcom_pdc_probe,
+	.driver = {
+		.name = "qcom-pdc",
+		.of_match_table = qcom_pdc_match_table,
+	},
+};
+module_platform_driver(qcom_pdc_driver);
+#else
 IRQCHIP_DECLARE(qcom_pdc, "qcom,pdc", qcom_pdc_init);
+#endif
+
+MODULE_DESCRIPTION("Qualcomm Technologies, Inc. Power Domain Controller");
+MODULE_LICENSE("GPL v2");
-- 
2.17.1

Re: [RFC][PATCH 3/5] irqchip: Allow QCOM_PDC to be loadable as a perment module

[Maulik Shah]

Hi,

On 6/16/2020 11:43 AM, John Stultz wrote:
> Allows qcom-pdc driver to be loaded as a permenent module

typo: permanent

> Also, due to the fact that IRQCHIP_DECLARE becomes a no-op when
> building as a module, we have to add the platform driver hooks
> explicitly.
>
> Thanks to Saravana for his help on pointing out the
> IRQCHIP_DECLARE issue and guidance on a solution.
>
> Cc: Andy Gross <agross@kernel.org>
> Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Jason Cooper <jason@lakedaemon.net>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Lina Iyer <ilina@codeaurora.org>
> Cc: Saravana Kannan <saravanak@google.com>
> Cc: Todd Kjos <tkjos@google.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: linux-arm-msm@vger.kernel.org
> Cc: iommu@lists.linux-foundation.org
> Cc: linux-gpio@vger.kernel.org
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
>   drivers/irqchip/Kconfig    |  2 +-
>   drivers/irqchip/qcom-pdc.c | 30 ++++++++++++++++++++++++++++++
>   2 files changed, 31 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
> index 29fead208cad..12765bed08f9 100644
> --- a/drivers/irqchip/Kconfig
> +++ b/drivers/irqchip/Kconfig
> @@ -425,7 +425,7 @@ config GOLDFISH_PIC
>            for Goldfish based virtual platforms.
>   
>   config QCOM_PDC
> -	bool "QCOM PDC"
> +	tristate "QCOM PDC"
>   	depends on ARCH_QCOM
>   	select IRQ_DOMAIN_HIERARCHY
>   	help
> diff --git a/drivers/irqchip/qcom-pdc.c b/drivers/irqchip/qcom-pdc.c
> index 6ae9e1f0819d..98d74160afcd 100644
> --- a/drivers/irqchip/qcom-pdc.c
> +++ b/drivers/irqchip/qcom-pdc.c
> @@ -11,7 +11,9 @@
>   #include <linux/irqdomain.h>
>   #include <linux/io.h>
>   #include <linux/kernel.h>
> +#include <linux/module.h>
>   #include <linux/of.h>
> +#include <linux/of_irq.h>
please move this include in order after of_device.h
>   #include <linux/of_address.h>
>   #include <linux/of_device.h>
>   #include <linux/soc/qcom/irq.h>
> @@ -430,4 +432,32 @@ static int qcom_pdc_init(struct device_node *node, struct device_node *parent)
>   	return ret;
>   }
>   
> +#ifdef MODULE
> +static int qcom_pdc_probe(struct platform_device *pdev)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	struct device_node *parent = of_irq_find_parent(np);
> +
> +	return qcom_pdc_init(np, parent);
> +}
> +
> +static const struct of_device_id qcom_pdc_match_table[] = {
> +	{ .compatible = "qcom,pdc" },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, qcom_pdc_match_table);
> +
> +static struct platform_driver qcom_pdc_driver = {
> +	.probe = qcom_pdc_probe,
> +	.driver = {
> +		.name = "qcom-pdc",
> +		.of_match_table = qcom_pdc_match_table,

can you please set .suppress_bind_attrs = true,

This is to prevent bind/unbind using sysfs. Once irqchip driver module 
is loaded, it shouldn't get unbind at runtime.

Thanks,
Maulik
> +	},
> +};
> +module_platform_driver(qcom_pdc_driver);
> +#else
>   IRQCHIP_DECLARE(qcom_pdc, "qcom,pdc", qcom_pdc_init);
> +#endif
> +
> +MODULE_DESCRIPTION("Qualcomm Technologies, Inc. Power Domain Controller");
> +MODULE_LICENSE("GPL v2");

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

Re: [RFC][PATCH 3/5] irqchip: Allow QCOM_PDC to be loadable as a perment module

[Lina Iyer]

On Tue, Jun 16 2020 at 05:30 -0600, Maulik Shah wrote:
>Hi,
>
>On 6/16/2020 11:43 AM, John Stultz wrote:
>>Allows qcom-pdc driver to be loaded as a permenent module
>
>typo: permanent
>
>>Also, due to the fact that IRQCHIP_DECLARE becomes a no-op when
>>building as a module, we have to add the platform driver hooks
>>explicitly.
>>
>>Thanks to Saravana for his help on pointing out the
>>IRQCHIP_DECLARE issue and guidance on a solution.
>>
>>Cc: Andy Gross <agross@kernel.org>
>>Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
>>Cc: Joerg Roedel <joro@8bytes.org>
>>Cc: Thomas Gleixner <tglx@linutronix.de>
>>Cc: Jason Cooper <jason@lakedaemon.net>
>>Cc: Marc Zyngier <maz@kernel.org>
>>Cc: Linus Walleij <linus.walleij@linaro.org>
>>Cc: Lina Iyer <ilina@codeaurora.org>
>>Cc: Saravana Kannan <saravanak@google.com>
>>Cc: Todd Kjos <tkjos@google.com>
>>Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>Cc: linux-arm-msm@vger.kernel.org
>>Cc: iommu@lists.linux-foundation.org
>>Cc: linux-gpio@vger.kernel.org
>>Signed-off-by: John Stultz <john.stultz@linaro.org>
>>---
>>  drivers/irqchip/Kconfig    |  2 +-
>>  drivers/irqchip/qcom-pdc.c | 30 ++++++++++++++++++++++++++++++
>>  2 files changed, 31 insertions(+), 1 deletion(-)
>>
>>diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
>>index 29fead208cad..12765bed08f9 100644
>>--- a/drivers/irqchip/Kconfig
>>+++ b/drivers/irqchip/Kconfig
>>@@ -425,7 +425,7 @@ config GOLDFISH_PIC
>>           for Goldfish based virtual platforms.
>>  config QCOM_PDC
>>-	bool "QCOM PDC"
>>+	tristate "QCOM PDC"
>>  	depends on ARCH_QCOM
>>  	select IRQ_DOMAIN_HIERARCHY
>>  	help
>>diff --git a/drivers/irqchip/qcom-pdc.c b/drivers/irqchip/qcom-pdc.c
>>index 6ae9e1f0819d..98d74160afcd 100644
>>--- a/drivers/irqchip/qcom-pdc.c
>>+++ b/drivers/irqchip/qcom-pdc.c
>>@@ -11,7 +11,9 @@
>>  #include <linux/irqdomain.h>
>>  #include <linux/io.h>
>>  #include <linux/kernel.h>
>>+#include <linux/module.h>
>>  #include <linux/of.h>
>>+#include <linux/of_irq.h>
>please move this include in order after of_device.h
>>  #include <linux/of_address.h>
>>  #include <linux/of_device.h>
>>  #include <linux/soc/qcom/irq.h>
>>@@ -430,4 +432,32 @@ static int qcom_pdc_init(struct device_node *node, struct device_node *parent)
>>  	return ret;
>>  }
>>+#ifdef MODULE
>>+static int qcom_pdc_probe(struct platform_device *pdev)
>>+{
>>+	struct device_node *np = pdev->dev.of_node;
>>+	struct device_node *parent = of_irq_find_parent(np);
>>+
>>+	return qcom_pdc_init(np, parent);
>>+}
>>+
>>+static const struct of_device_id qcom_pdc_match_table[] = {
>>+	{ .compatible = "qcom,pdc" },
>>+	{}
>>+};
>>+MODULE_DEVICE_TABLE(of, qcom_pdc_match_table);
>>+
>>+static struct platform_driver qcom_pdc_driver = {
>>+	.probe = qcom_pdc_probe,
>>+	.driver = {
>>+		.name = "qcom-pdc",
>>+		.of_match_table = qcom_pdc_match_table,
>
>can you please set .suppress_bind_attrs = true,
>
>This is to prevent bind/unbind using sysfs. Once irqchip driver module 
>is loaded, it shouldn't get unbind at runtime.
>
That is a good point. We probably should do that to RPMH RSC driver as well.

>Thanks,
>Maulik
>>+	},
>>+};
>>+module_platform_driver(qcom_pdc_driver);
>>+#else
>>  IRQCHIP_DECLARE(qcom_pdc, "qcom,pdc", qcom_pdc_init);
>>+#endif
>>+
>>+MODULE_DESCRIPTION("Qualcomm Technologies, Inc. Power Domain Controller");
>>+MODULE_LICENSE("GPL v2");
>
>-- 
>QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
>

Re: [RFC][PATCH 3/5] irqchip: Allow QCOM_PDC to be loadable as a perment module

[John Stultz]

On Tue, Jun 16, 2020 at 4:30 AM Maulik Shah <mkshah@codeaurora.org> wrote:
>
> Hi,
>
> On 6/16/2020 11:43 AM, John Stultz wrote:
> > Allows qcom-pdc driver to be loaded as a permenent module
>
> typo: permanent
>
> > Also, due to the fact that IRQCHIP_DECLARE becomes a no-op when
> > building as a module, we have to add the platform driver hooks
> > explicitly.
> >
> > Thanks to Saravana for his help on pointing out the
> > IRQCHIP_DECLARE issue and guidance on a solution.
> >
> > Cc: Andy Gross <agross@kernel.org>
> > Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
> > Cc: Joerg Roedel <joro@8bytes.org>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Jason Cooper <jason@lakedaemon.net>
> > Cc: Marc Zyngier <maz@kernel.org>
> > Cc: Linus Walleij <linus.walleij@linaro.org>
> > Cc: Lina Iyer <ilina@codeaurora.org>
> > Cc: Saravana Kannan <saravanak@google.com>
> > Cc: Todd Kjos <tkjos@google.com>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: linux-arm-msm@vger.kernel.org
> > Cc: iommu@lists.linux-foundation.org
> > Cc: linux-gpio@vger.kernel.org
> > Signed-off-by: John Stultz <john.stultz@linaro.org>
> > ---
> >   drivers/irqchip/Kconfig    |  2 +-
> >   drivers/irqchip/qcom-pdc.c | 30 ++++++++++++++++++++++++++++++
> >   2 files changed, 31 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
> > index 29fead208cad..12765bed08f9 100644
> > --- a/drivers/irqchip/Kconfig
> > +++ b/drivers/irqchip/Kconfig
> > @@ -425,7 +425,7 @@ config GOLDFISH_PIC
> >            for Goldfish based virtual platforms.
> >
> >   config QCOM_PDC
> > -     bool "QCOM PDC"
> > +     tristate "QCOM PDC"
> >       depends on ARCH_QCOM
> >       select IRQ_DOMAIN_HIERARCHY
> >       help
> > diff --git a/drivers/irqchip/qcom-pdc.c b/drivers/irqchip/qcom-pdc.c
> > index 6ae9e1f0819d..98d74160afcd 100644
> > --- a/drivers/irqchip/qcom-pdc.c
> > +++ b/drivers/irqchip/qcom-pdc.c
> > @@ -11,7 +11,9 @@
> >   #include <linux/irqdomain.h>
> >   #include <linux/io.h>
> >   #include <linux/kernel.h>
> > +#include <linux/module.h>
> >   #include <linux/of.h>
> > +#include <linux/of_irq.h>
> please move this include in order after of_device.h
> >   #include <linux/of_address.h>
> >   #include <linux/of_device.h>
> >   #include <linux/soc/qcom/irq.h>
> > @@ -430,4 +432,32 @@ static int qcom_pdc_init(struct device_node *node, struct device_node *parent)
> >       return ret;
> >   }
> >
> > +#ifdef MODULE
> > +static int qcom_pdc_probe(struct platform_device *pdev)
> > +{
> > +     struct device_node *np = pdev->dev.of_node;
> > +     struct device_node *parent = of_irq_find_parent(np);
> > +
> > +     return qcom_pdc_init(np, parent);
> > +}
> > +
> > +static const struct of_device_id qcom_pdc_match_table[] = {
> > +     { .compatible = "qcom,pdc" },
> > +     {}
> > +};
> > +MODULE_DEVICE_TABLE(of, qcom_pdc_match_table);
> > +
> > +static struct platform_driver qcom_pdc_driver = {
> > +     .probe = qcom_pdc_probe,
> > +     .driver = {
> > +             .name = "qcom-pdc",
> > +             .of_match_table = qcom_pdc_match_table,
>
> can you please set .suppress_bind_attrs = true,
>
> This is to prevent bind/unbind using sysfs. Once irqchip driver module
> is loaded, it shouldn't get unbind at runtime.

Thanks, I really appreciate the review! I've made these changes on my
side and they'll be included in v2.

thanks
-john

[RFC][PATCH 4/5] pinctrl: qcom: Allow pinctrl-msm code to be loadable as a module

[John Stultz]

Tweaks to allow pinctrl-msm code to be loadable as a module.
This is needed in order to support having the qcom-scm driver,
which pinctrl-msm calls into, configured as a module.

Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-arm-msm@vger.kernel.org
Cc: iommu@lists.linux-foundation.org
Cc: linux-gpio@vger.kernel.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 drivers/pinctrl/qcom/Kconfig       | 2 +-
 drivers/pinctrl/qcom/pinctrl-msm.c | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/pinctrl/qcom/Kconfig b/drivers/pinctrl/qcom/Kconfig
index ff1ee159dca2..5a7e1bc621e6 100644
--- a/drivers/pinctrl/qcom/Kconfig
+++ b/drivers/pinctrl/qcom/Kconfig
@@ -2,7 +2,7 @@
 if (ARCH_QCOM || COMPILE_TEST)
 
 config PINCTRL_MSM
-	bool
+	tristate
 	select PINMUX
 	select PINCONF
 	select GENERIC_PINCONF
diff --git a/drivers/pinctrl/qcom/pinctrl-msm.c b/drivers/pinctrl/qcom/pinctrl-msm.c
index 83b7d64bc4c1..54a226f682e9 100644
--- a/drivers/pinctrl/qcom/pinctrl-msm.c
+++ b/drivers/pinctrl/qcom/pinctrl-msm.c
@@ -1355,3 +1355,6 @@ int msm_pinctrl_remove(struct platform_device *pdev)
 }
 EXPORT_SYMBOL(msm_pinctrl_remove);
 
+MODULE_DESCRIPTION("Qualcomm Technologies, Inc. pinctrl-msm driver");
+MODULE_LICENSE("GPL v2");
+
-- 
2.17.1

Re: [RFC][PATCH 4/5] pinctrl: qcom: Allow pinctrl-msm code to be loadable as a module

[Linus Walleij]

On Tue, Jun 16, 2020 at 8:13 AM John Stultz <john.stultz@linaro.org> wrote:

> Tweaks to allow pinctrl-msm code to be loadable as a module.
> This is needed in order to support having the qcom-scm driver,
> which pinctrl-msm calls into, configured as a module.
>
> Cc: Andy Gross <agross@kernel.org>
> Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Jason Cooper <jason@lakedaemon.net>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Lina Iyer <ilina@codeaurora.org>
> Cc: Saravana Kannan <saravanak@google.com>
> Cc: Todd Kjos <tkjos@google.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: linux-arm-msm@vger.kernel.org
> Cc: iommu@lists.linux-foundation.org
> Cc: linux-gpio@vger.kernel.org
> Signed-off-by: John Stultz <john.stultz@linaro.org>

Unless there are dependencies on the irqchip patches I can apply
this if Bjorn is OK with it.

Yours,
Linus Walleij

Re: [RFC][PATCH 4/5] pinctrl: qcom: Allow pinctrl-msm code to be loadable as a module

[Bjorn Andersson]

On Mon 15 Jun 23:13 PDT 2020, John Stultz wrote:

> Tweaks to allow pinctrl-msm code to be loadable as a module.
> This is needed in order to support having the qcom-scm driver,
> which pinctrl-msm calls into, configured as a module.
> 

This means that we need a "depends on QCOM_SCM || QCOM_SCM=n" on all
entries in the Kconfig that selects PINCTRL_MSM, or switch PINCTRL_MSM
to be user selectable and make all the others depend on it.

> Cc: Andy Gross <agross@kernel.org>
> Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Jason Cooper <jason@lakedaemon.net>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Lina Iyer <ilina@codeaurora.org>
> Cc: Saravana Kannan <saravanak@google.com>
> Cc: Todd Kjos <tkjos@google.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: linux-arm-msm@vger.kernel.org
> Cc: iommu@lists.linux-foundation.org
> Cc: linux-gpio@vger.kernel.org
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
>  drivers/pinctrl/qcom/Kconfig       | 2 +-
>  drivers/pinctrl/qcom/pinctrl-msm.c | 3 +++
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pinctrl/qcom/Kconfig b/drivers/pinctrl/qcom/Kconfig
> index ff1ee159dca2..5a7e1bc621e6 100644
> --- a/drivers/pinctrl/qcom/Kconfig
> +++ b/drivers/pinctrl/qcom/Kconfig
> @@ -2,7 +2,7 @@
>  if (ARCH_QCOM || COMPILE_TEST)
>  
>  config PINCTRL_MSM
> -	bool
> +	tristate
>  	select PINMUX
>  	select PINCONF
>  	select GENERIC_PINCONF
> diff --git a/drivers/pinctrl/qcom/pinctrl-msm.c b/drivers/pinctrl/qcom/pinctrl-msm.c
> index 83b7d64bc4c1..54a226f682e9 100644
> --- a/drivers/pinctrl/qcom/pinctrl-msm.c
> +++ b/drivers/pinctrl/qcom/pinctrl-msm.c
> @@ -1355,3 +1355,6 @@ int msm_pinctrl_remove(struct platform_device *pdev)
>  }
>  EXPORT_SYMBOL(msm_pinctrl_remove);
>  
> +MODULE_DESCRIPTION("Qualcomm Technologies, Inc. pinctrl-msm driver");

It's the "Qualcomm Technologies, Inc. TLMM driver"

> +MODULE_LICENSE("GPL v2");
> +

Please don't retain my empty line at the end of this file :)

Regards,
Bjorn

> -- 
> 2.17.1
> 

Re: [RFC][PATCH 4/5] pinctrl: qcom: Allow pinctrl-msm code to be loadable as a module

[John Stultz]

On Sat, Jun 20, 2020 at 11:03 PM Bjorn Andersson
<bjorn.andersson@linaro.org> wrote:
>
> On Mon 15 Jun 23:13 PDT 2020, John Stultz wrote:
>
> > Tweaks to allow pinctrl-msm code to be loadable as a module.
> > This is needed in order to support having the qcom-scm driver,
> > which pinctrl-msm calls into, configured as a module.
> >
>
> This means that we need a "depends on QCOM_SCM || QCOM_SCM=n" on all
> entries in the Kconfig that selects PINCTRL_MSM, or switch PINCTRL_MSM
> to be user selectable and make all the others depend on it.

Oh, good point! I already had to fix that in a different tree, but
forgot to move the fix over to my upstreaming tree.


> >
> > +MODULE_DESCRIPTION("Qualcomm Technologies, Inc. pinctrl-msm driver");
>
> It's the "Qualcomm Technologies, Inc. TLMM driver"
>
> > +MODULE_LICENSE("GPL v2");
> > +
>
> Please don't retain my empty line at the end of this file :)

Done and done. Thanks so much for the review!
-john

[RFC][PATCH 5/5] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module

[John Stultz]

Allow the qcom_scm driver to be loadable as a
permenent module.

Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-arm-msm@vger.kernel.org
Cc: iommu@lists.linux-foundation.org
Cc: linux-gpio@vger.kernel.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 drivers/firmware/Kconfig    | 2 +-
 drivers/firmware/Makefile   | 3 ++-
 drivers/firmware/qcom_scm.c | 4 ++++
 drivers/iommu/Kconfig       | 2 ++
 4 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index fbd785dd0513..9e533a462bf4 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -236,7 +236,7 @@ config INTEL_STRATIX10_RSU
 	  Say Y here if you want Intel RSU support.
 
 config QCOM_SCM
-	bool
+	tristate "Qcom SCM driver"
 	depends on ARM || ARM64
 	select RESET_CONTROLLER
 
diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
index 99510be9f5ed..cf24d674216b 100644
--- a/drivers/firmware/Makefile
+++ b/drivers/firmware/Makefile
@@ -17,7 +17,8 @@ obj-$(CONFIG_ISCSI_IBFT)	+= iscsi_ibft.o
 obj-$(CONFIG_FIRMWARE_MEMMAP)	+= memmap.o
 obj-$(CONFIG_RASPBERRYPI_FIRMWARE) += raspberrypi.o
 obj-$(CONFIG_FW_CFG_SYSFS)	+= qemu_fw_cfg.o
-obj-$(CONFIG_QCOM_SCM)		+= qcom_scm.o qcom_scm-smc.o qcom_scm-legacy.o
+obj-$(CONFIG_QCOM_SCM)		+= qcom-scm.o
+qcom-scm-objs += qcom_scm.o qcom_scm-smc.o qcom_scm-legacy.o
 obj-$(CONFIG_TI_SCI_PROTOCOL)	+= ti_sci.o
 obj-$(CONFIG_TRUSTED_FOUNDATIONS) += trusted_foundations.o
 obj-$(CONFIG_TURRIS_MOX_RWTM)	+= turris-mox-rwtm.o
diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index 0e7233a20f34..b5e88bf66975 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -1155,6 +1155,7 @@ static const struct of_device_id qcom_scm_dt_match[] = {
 	{ .compatible = "qcom,scm" },
 	{}
 };
+MODULE_DEVICE_TABLE(of, qcom_scm_dt_match);
 
 static struct platform_driver qcom_scm_driver = {
 	.driver = {
@@ -1170,3 +1171,6 @@ static int __init qcom_scm_init(void)
 	return platform_driver_register(&qcom_scm_driver);
 }
 subsys_initcall(qcom_scm_init);
+
+MODULE_DESCRIPTION("Qualcomm Technologies, Inc. SCM driver");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index b510f67dfa49..714893535dd2 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -381,6 +381,7 @@ config SPAPR_TCE_IOMMU
 config ARM_SMMU
 	tristate "ARM Ltd. System MMU (SMMU) Support"
 	depends on (ARM64 || ARM || (COMPILE_TEST && !GENERIC_ATOMIC64)) && MMU
+	depends on QCOM_SCM || !QCOM_SCM #if QCOM_SCM=m this can't be =y
 	select IOMMU_API
 	select IOMMU_IO_PGTABLE_LPAE
 	select ARM_DMA_USE_IOMMU if ARM
@@ -500,6 +501,7 @@ config QCOM_IOMMU
 	# Note: iommu drivers cannot (yet?) be built as modules
 	bool "Qualcomm IOMMU Support"
 	depends on ARCH_QCOM || (COMPILE_TEST && !GENERIC_ATOMIC64)
+	depends on QCOM_SCM=y
 	select IOMMU_API
 	select IOMMU_IO_PGTABLE_LPAE
 	select ARM_DMA_USE_IOMMU
-- 
2.17.1

Re: [RFC][PATCH 5/5] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module

[Marc Zyngier]

Hi John,

+Will for the SMMU part.

On 2020-06-16 07:13, John Stultz wrote:
> Allow the qcom_scm driver to be loadable as a
> permenent module.
> 
> Cc: Andy Gross <agross@kernel.org>
> Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Jason Cooper <jason@lakedaemon.net>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Lina Iyer <ilina@codeaurora.org>
> Cc: Saravana Kannan <saravanak@google.com>
> Cc: Todd Kjos <tkjos@google.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: linux-arm-msm@vger.kernel.org
> Cc: iommu@lists.linux-foundation.org
> Cc: linux-gpio@vger.kernel.org
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
>  drivers/firmware/Kconfig    | 2 +-
>  drivers/firmware/Makefile   | 3 ++-
>  drivers/firmware/qcom_scm.c | 4 ++++
>  drivers/iommu/Kconfig       | 2 ++
>  4 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
> index fbd785dd0513..9e533a462bf4 100644
> --- a/drivers/firmware/Kconfig
> +++ b/drivers/firmware/Kconfig
> @@ -236,7 +236,7 @@ config INTEL_STRATIX10_RSU
>  	  Say Y here if you want Intel RSU support.
> 
>  config QCOM_SCM
> -	bool
> +	tristate "Qcom SCM driver"
>  	depends on ARM || ARM64
>  	select RESET_CONTROLLER
> 
> diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
> index 99510be9f5ed..cf24d674216b 100644
> --- a/drivers/firmware/Makefile
> +++ b/drivers/firmware/Makefile
> @@ -17,7 +17,8 @@ obj-$(CONFIG_ISCSI_IBFT)	+= iscsi_ibft.o
>  obj-$(CONFIG_FIRMWARE_MEMMAP)	+= memmap.o
>  obj-$(CONFIG_RASPBERRYPI_FIRMWARE) += raspberrypi.o
>  obj-$(CONFIG_FW_CFG_SYSFS)	+= qemu_fw_cfg.o
> -obj-$(CONFIG_QCOM_SCM)		+= qcom_scm.o qcom_scm-smc.o qcom_scm-legacy.o
> +obj-$(CONFIG_QCOM_SCM)		+= qcom-scm.o
> +qcom-scm-objs += qcom_scm.o qcom_scm-smc.o qcom_scm-legacy.o
>  obj-$(CONFIG_TI_SCI_PROTOCOL)	+= ti_sci.o
>  obj-$(CONFIG_TRUSTED_FOUNDATIONS) += trusted_foundations.o
>  obj-$(CONFIG_TURRIS_MOX_RWTM)	+= turris-mox-rwtm.o
> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> index 0e7233a20f34..b5e88bf66975 100644
> --- a/drivers/firmware/qcom_scm.c
> +++ b/drivers/firmware/qcom_scm.c
> @@ -1155,6 +1155,7 @@ static const struct of_device_id 
> qcom_scm_dt_match[] = {
>  	{ .compatible = "qcom,scm" },
>  	{}
>  };
> +MODULE_DEVICE_TABLE(of, qcom_scm_dt_match);
> 
>  static struct platform_driver qcom_scm_driver = {
>  	.driver = {
> @@ -1170,3 +1171,6 @@ static int __init qcom_scm_init(void)
>  	return platform_driver_register(&qcom_scm_driver);
>  }
>  subsys_initcall(qcom_scm_init);
> +
> +MODULE_DESCRIPTION("Qualcomm Technologies, Inc. SCM driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index b510f67dfa49..714893535dd2 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -381,6 +381,7 @@ config SPAPR_TCE_IOMMU
>  config ARM_SMMU
>  	tristate "ARM Ltd. System MMU (SMMU) Support"
>  	depends on (ARM64 || ARM || (COMPILE_TEST && !GENERIC_ATOMIC64)) && 
> MMU
> +	depends on QCOM_SCM || !QCOM_SCM #if QCOM_SCM=m this can't be =y

This looks a bit ugly. Could you explain why we need this at the SMMU 
level? I'd have expected the dependency to flow the other way around...

>  	select IOMMU_API
>  	select IOMMU_IO_PGTABLE_LPAE
>  	select ARM_DMA_USE_IOMMU if ARM
> @@ -500,6 +501,7 @@ config QCOM_IOMMU
>  	# Note: iommu drivers cannot (yet?) be built as modules
>  	bool "Qualcomm IOMMU Support"
>  	depends on ARCH_QCOM || (COMPILE_TEST && !GENERIC_ATOMIC64)
> +	depends on QCOM_SCM=y
>  	select IOMMU_API
>  	select IOMMU_IO_PGTABLE_LPAE
>  	select ARM_DMA_USE_IOMMU

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...

Re: [RFC][PATCH 5/5] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module

[John Stultz]

On Tue, Jun 16, 2020 at 12:55 AM Marc Zyngier <maz@kernel.org> wrote:
> On 2020-06-16 07:13, John Stultz wrote:
> > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > index b510f67dfa49..714893535dd2 100644
> > --- a/drivers/iommu/Kconfig
> > +++ b/drivers/iommu/Kconfig
> > @@ -381,6 +381,7 @@ config SPAPR_TCE_IOMMU
> >  config ARM_SMMU
> >       tristate "ARM Ltd. System MMU (SMMU) Support"
> >       depends on (ARM64 || ARM || (COMPILE_TEST && !GENERIC_ATOMIC64)) &&
> > MMU
> > +     depends on QCOM_SCM || !QCOM_SCM #if QCOM_SCM=m this can't be =y
>
> This looks a bit ugly. Could you explain why we need this at the SMMU
> level? I'd have expected the dependency to flow the other way around...

Yea, so the arm-smmu-qcom.c file calls directly into the qcom-scm code
via qcom_scm_qsmmu500_wait_safe_toggle()
  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/iommu/arm-smmu-qcom.c?h=v5.8-rc1#n44

So if ARM_SMMU=y and QCOM_SCM=m we get:
drivers/iommu/arm-smmu-qcom.o: In function `qcom_smmu500_reset':
arm-smmu-qcom.c:(.text+0xb4): undefined reference to
`qcom_scm_qsmmu500_wait_safe_toggle'

Do you have a suggestion for an alternative approach?

thanks
-john

Re: [RFC][PATCH 5/5] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module

[Will Deacon]

On Tue, Jun 16, 2020 at 01:52:32PM -0700, John Stultz wrote:
> On Tue, Jun 16, 2020 at 12:55 AM Marc Zyngier <maz@kernel.org> wrote:
> > On 2020-06-16 07:13, John Stultz wrote:
> > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > > index b510f67dfa49..714893535dd2 100644
> > > --- a/drivers/iommu/Kconfig
> > > +++ b/drivers/iommu/Kconfig
> > > @@ -381,6 +381,7 @@ config SPAPR_TCE_IOMMU
> > >  config ARM_SMMU
> > >       tristate "ARM Ltd. System MMU (SMMU) Support"
> > >       depends on (ARM64 || ARM || (COMPILE_TEST && !GENERIC_ATOMIC64)) &&
> > > MMU
> > > +     depends on QCOM_SCM || !QCOM_SCM #if QCOM_SCM=m this can't be =y
> >
> > This looks a bit ugly. Could you explain why we need this at the SMMU
> > level? I'd have expected the dependency to flow the other way around...
> 
> Yea, so the arm-smmu-qcom.c file calls directly into the qcom-scm code
> via qcom_scm_qsmmu500_wait_safe_toggle()
>   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/iommu/arm-smmu-qcom.c?h=v5.8-rc1#n44
> 
> So if ARM_SMMU=y and QCOM_SCM=m we get:
> drivers/iommu/arm-smmu-qcom.o: In function `qcom_smmu500_reset':
> arm-smmu-qcom.c:(.text+0xb4): undefined reference to
> `qcom_scm_qsmmu500_wait_safe_toggle'
> 
> Do you have a suggestion for an alternative approach?

Can you use symbol_get() or something like that? How are module dependencies
handled by other drivers?

Will

Re: [RFC][PATCH 5/5] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module

[Vinod Koul]

On 03-07-20, 13:23, Will Deacon wrote:
> On Tue, Jun 16, 2020 at 01:52:32PM -0700, John Stultz wrote:
> > On Tue, Jun 16, 2020 at 12:55 AM Marc Zyngier <maz@kernel.org> wrote:
> > > On 2020-06-16 07:13, John Stultz wrote:
> > > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > > > index b510f67dfa49..714893535dd2 100644
> > > > --- a/drivers/iommu/Kconfig
> > > > +++ b/drivers/iommu/Kconfig
> > > > @@ -381,6 +381,7 @@ config SPAPR_TCE_IOMMU
> > > >  config ARM_SMMU
> > > >       tristate "ARM Ltd. System MMU (SMMU) Support"
> > > >       depends on (ARM64 || ARM || (COMPILE_TEST && !GENERIC_ATOMIC64)) &&
> > > > MMU
> > > > +     depends on QCOM_SCM || !QCOM_SCM #if QCOM_SCM=m this can't be =y
> > >
> > > This looks a bit ugly. Could you explain why we need this at the SMMU
> > > level? I'd have expected the dependency to flow the other way around...
> > 
> > Yea, so the arm-smmu-qcom.c file calls directly into the qcom-scm code
> > via qcom_scm_qsmmu500_wait_safe_toggle()
> >   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/iommu/arm-smmu-qcom.c?h=v5.8-rc1#n44
> > 
> > So if ARM_SMMU=y and QCOM_SCM=m we get:
> > drivers/iommu/arm-smmu-qcom.o: In function `qcom_smmu500_reset':
> > arm-smmu-qcom.c:(.text+0xb4): undefined reference to
> > `qcom_scm_qsmmu500_wait_safe_toggle'
> > 
> > Do you have a suggestion for an alternative approach?
> 
> Can you use symbol_get() or something like that? How are module dependencies
> handled by other drivers?

So drivers deal with this by making rules in Kconfig which will prohibit
this case. QCOM_SCM depends on ARM_SMMU with the caveat that if ARM_SMMU
is a module, QCOM_SCM cant be inbuilt.

This can be done by adding below line in Kconfig for QCOM_SCM:

        depends on ARM_SMMU || !ARM_SMMU

This is quite prevalent is drivers to ensure dependency like this

Thanks
-- 
~Vinod