diff mbox series

[v2,5/5] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module

Message ID 20200625001039.56174-6-john.stultz@linaro.org
State New
Headers show
Series Allow for qcom-pdc, pinctrl-msm and qcom-scm drivers to be loadable as modules | expand

Commit Message

John Stultz June 25, 2020, 12:10 a.m. UTC
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: Maulik Shah <mkshah@codeaurora.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(-)

Comments

Greg Kroah-Hartman July 2, 2020, 12:47 p.m. UTC | #1
On Thu, Jun 25, 2020 at 12:10:39AM +0000, 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: Maulik Shah <mkshah@codeaurora.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>


Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Will Deacon July 2, 2020, 2:18 p.m. UTC | #2
On Thu, Jun 25, 2020 at 12:10:39AM +0000, 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
>  	select IOMMU_API
>  	select IOMMU_IO_PGTABLE_LPAE
>  	select ARM_DMA_USE_IOMMU if ARM

This looks like a giant hack. Is there another way to handle this?

Will
John Stultz July 10, 2020, 3:28 a.m. UTC | #3
On Thu, Jul 2, 2020 at 7:18 AM Will Deacon <will@kernel.org> wrote:
> On Thu, Jun 25, 2020 at 12:10:39AM +0000, 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
> >       select IOMMU_API
> >       select IOMMU_IO_PGTABLE_LPAE
> >       select ARM_DMA_USE_IOMMU if ARM
>
> This looks like a giant hack. Is there another way to handle this?

Sorry for the slow response here.

So, I agree the syntax looks strange (requiring a comment obviously
isn't a good sign), but it's a fairly common way to ensure drivers
don't get built in if they optionally depend on another driver that
can be built as a module.
  See "RFKILL || !RFKILL", "EXTCON || !EXTCON", or "USB_GADGET ||
!USB_GADGET" in various Kconfig files.

I'm open to using a different method, and in a different thread you
suggested using something like symbol_get(). I need to look into it
more, but that approach looks even more messy and prone to runtime
failures. Blocking the unwanted case at build time seems a bit cleaner
to me, even if the syntax is odd.

thanks
-john
Will Deacon July 10, 2020, 7:54 a.m. UTC | #4
On Thu, Jul 09, 2020 at 08:28:45PM -0700, John Stultz wrote:
> On Thu, Jul 2, 2020 at 7:18 AM Will Deacon <will@kernel.org> wrote:
> > On Thu, Jun 25, 2020 at 12:10:39AM +0000, 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
> > >       select IOMMU_API
> > >       select IOMMU_IO_PGTABLE_LPAE
> > >       select ARM_DMA_USE_IOMMU if ARM
> >
> > This looks like a giant hack. Is there another way to handle this?
> 
> Sorry for the slow response here.
> 
> So, I agree the syntax looks strange (requiring a comment obviously
> isn't a good sign), but it's a fairly common way to ensure drivers
> don't get built in if they optionally depend on another driver that
> can be built as a module.
>   See "RFKILL || !RFKILL", "EXTCON || !EXTCON", or "USB_GADGET ||
> !USB_GADGET" in various Kconfig files.
> 
> I'm open to using a different method, and in a different thread you
> suggested using something like symbol_get(). I need to look into it
> more, but that approach looks even more messy and prone to runtime
> failures. Blocking the unwanted case at build time seems a bit cleaner
> to me, even if the syntax is odd.

Maybe just split it out then, so that the ARM_SMMU entry doesn't have this,
as that driver _really_ doesn't care about SoC details like this. In other
words, add a new entry along the lines of:

	config ARM_SMMU_QCOM_IMPL
	default y
	#if QCOM_SCM=m this can't be =y
	depends on ARM_SMMU & (QCOM_SCM || !QCOM_SCM)

and then have arm-smmu.h provide a static inline qcom_smmu_impl_init()
which returns -ENODEV if CONFIG_ARM_SMMU_QCOM_IMPL=n and hack the Makefile
so that we don't bother to compile arm-smmu-qcom.o in that case.

Would that work?

Will
John Stultz July 10, 2020, 10:21 p.m. UTC | #5
On Fri, Jul 10, 2020 at 12:54 AM Will Deacon <will@kernel.org> wrote:
> On Thu, Jul 09, 2020 at 08:28:45PM -0700, John Stultz wrote:
> > On Thu, Jul 2, 2020 at 7:18 AM Will Deacon <will@kernel.org> wrote:
> > > On Thu, Jun 25, 2020 at 12:10:39AM +0000, 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
> > > >       select IOMMU_API
> > > >       select IOMMU_IO_PGTABLE_LPAE
> > > >       select ARM_DMA_USE_IOMMU if ARM
> > >
> > > This looks like a giant hack. Is there another way to handle this?
> >
> > Sorry for the slow response here.
> >
> > So, I agree the syntax looks strange (requiring a comment obviously
> > isn't a good sign), but it's a fairly common way to ensure drivers
> > don't get built in if they optionally depend on another driver that
> > can be built as a module.
> >   See "RFKILL || !RFKILL", "EXTCON || !EXTCON", or "USB_GADGET ||
> > !USB_GADGET" in various Kconfig files.
> >
> > I'm open to using a different method, and in a different thread you
> > suggested using something like symbol_get(). I need to look into it
> > more, but that approach looks even more messy and prone to runtime
> > failures. Blocking the unwanted case at build time seems a bit cleaner
> > to me, even if the syntax is odd.
>
> Maybe just split it out then, so that the ARM_SMMU entry doesn't have this,
> as that driver _really_ doesn't care about SoC details like this. In other
> words, add a new entry along the lines of:
>
>         config ARM_SMMU_QCOM_IMPL
>         default y
>         #if QCOM_SCM=m this can't be =y
>         depends on ARM_SMMU & (QCOM_SCM || !QCOM_SCM)
>
> and then have arm-smmu.h provide a static inline qcom_smmu_impl_init()
> which returns -ENODEV if CONFIG_ARM_SMMU_QCOM_IMPL=n and hack the Makefile
> so that we don't bother to compile arm-smmu-qcom.o in that case.
>
> Would that work?

I think this proposal still has problems with the directionality of the call.

The arm-smmu-impl.o calls to arm-smmu-qcom.o which calls qcom_scm.o
So if qcom_scm.o is part of a module, the calling code in
arm-smmu-qcom.o also needs to be a module, which means CONFIG_ARM_SMMU
needs to be a module.

I know you said the arm-smmu driver doesn't care about SoC details,
but the trouble is that currently the arm-smmu driver does directly
call the qcom-scm code. So it is a real dependency. However, if
QCOM_SCM is not configured, it calls stubs and that's ok.  In that
way, the "depends on QCOM_SCM || !QCOM_SCM" line actually makes sense.
It looks terrible because we're used to boolean logic, but it's
ternary.

Maybe can have the ARM_SMMU_QCOM_IMPL approach you suggest above, but
that just holds the issue out at arms length, because we're still
going to need to have:
  depends on ARM_SMMU_QCOM_IMPL || !ARM_SMMU_QCOM_IMPL
in the ARM_SMMU definition, which I suspect you're wanting to avoid.

Otherwise the only thing I can think of is a deeper reworking of the
arm-smmu-impl code so that the arm-smmu-qcom code probes itself and
registers its hooks with the arm-smmu core.
That way the arm-smmu driver would not directly call any SoC specific
code (and thus have no dependencies outward). But it's probably a fair
amount of churn vs the extra depends string.

thanks
-john
diff mbox series

Patch

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