[PATCH 0/2] Add new reg_update_bits() support

[PATCH 0/2] Add new reg_update_bits() support

[Baolin Wang]

The Spreadtrum platform uses a special set/clear method to update
registers' bits, thus this patch set registers a physical regmap
bus into syscon core to support this feature instead of using the
MMIO bus, which is not a physical regmap bus.

Any comments are welcome. Thanks.

Changes from RFC v2:
 - Drop regmap change, which was applied by Mark.
 - Add more information about how to use set/clear.
 - Add checking to ensure the platform is compatible with
 using a new physical regmap bus.
 
Changes from RFC v1:
 - Add new helper to registers a physical regmap bus instead of
 using the MMIO bus.

Baolin Wang (2):
  mfd: syscon: Support physical regmap bus
  soc: sprd: Add Spreadtrum special bits updating support

 drivers/mfd/syscon.c           | 23 +++++++++-
 drivers/soc/Kconfig            |  1 +
 drivers/soc/Makefile           |  1 +
 drivers/soc/sprd/Kconfig       | 16 +++++++
 drivers/soc/sprd/Makefile      |  2 +
 drivers/soc/sprd/sprd_syscon.c | 82 ++++++++++++++++++++++++++++++++++
 include/linux/mfd/syscon.h     |  7 +++
 7 files changed, 130 insertions(+), 2 deletions(-)
 create mode 100644 drivers/soc/sprd/Kconfig
 create mode 100644 drivers/soc/sprd/Makefile
 create mode 100644 drivers/soc/sprd/sprd_syscon.c

-- 
2.17.1

[PATCH 1/2] mfd: syscon: Support physical regmap bus

[Baolin Wang]

Some platforms such as Spreadtrum platform, define a special method to
update bits of the registers instead of reading and writing, which means
we should use a physical regmap bus to define the reg_update_bits()
operation instead of the MMIO regmap bus.

Thus add a new helper for the syscon driver to allow to register a physical
regmap bus to support this new requirement.

Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
---
 drivers/mfd/syscon.c       | 23 +++++++++++++++++++++--
 include/linux/mfd/syscon.h |  7 +++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
index 3a97816d0cba..92bfe87038ca 100644
--- a/drivers/mfd/syscon.c
+++ b/drivers/mfd/syscon.c
@@ -24,6 +24,7 @@
 #include <linux/slab.h>
 
 static struct platform_driver syscon_driver;
+static struct regmap_bus *syscon_phy_regmap_bus;
 
 static DEFINE_SPINLOCK(syscon_list_slock);
 static LIST_HEAD(syscon_list);
@@ -106,14 +107,25 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
 	syscon_config.val_bits = reg_io_width * 8;
 	syscon_config.max_register = resource_size(&res) - reg_io_width;
 
-	regmap = regmap_init_mmio(NULL, base, &syscon_config);
+	 /*
+	  * The Spreadtrum syscon need register a real physical regmap bus
+	  * with new atomic bits updating operation instead of using
+	  * read-modify-write.
+	  */
+	if (IS_ENABLED(CONFIG_ARCH_SPRD) &&
+	    of_device_is_compatible(np, "sprd,atomic-syscon") &&
+	    syscon_phy_regmap_bus)
+		regmap = regmap_init(NULL, syscon_phy_regmap_bus, base,
+				     &syscon_config);
+	else
+		regmap = regmap_init_mmio(NULL, base, &syscon_config);
 	if (IS_ERR(regmap)) {
 		pr_err("regmap init failed\n");
 		ret = PTR_ERR(regmap);
 		goto err_regmap;
 	}
 
-	if (check_clk) {
+	if (check_clk && !syscon_phy_regmap_bus) {
 		clk = of_clk_get(np, 0);
 		if (IS_ERR(clk)) {
 			ret = PTR_ERR(clk);
@@ -172,6 +184,13 @@ static struct regmap *device_node_get_regmap(struct device_node *np,
 	return syscon->regmap;
 }
 
+void syscon_register_phys_regmap_bus(struct regmap_bus *phy_regmap_bus)
+{
+	if (phy_regmap_bus)
+		syscon_phy_regmap_bus = phy_regmap_bus;
+}
+EXPORT_SYMBOL_GPL(syscon_register_phys_regmap_bus);
+
 struct regmap *device_node_to_regmap(struct device_node *np)
 {
 	return device_node_get_regmap(np, false);
diff --git a/include/linux/mfd/syscon.h b/include/linux/mfd/syscon.h
index 7f20e9b502a5..fbc2a2f0f414 100644
--- a/include/linux/mfd/syscon.h
+++ b/include/linux/mfd/syscon.h
@@ -13,6 +13,7 @@
 
 #include <linux/err.h>
 #include <linux/errno.h>
+#include <linux/regmap.h>
 
 struct device_node;
 
@@ -28,6 +29,7 @@ extern struct regmap *syscon_regmap_lookup_by_phandle_args(
 					const char *property,
 					int arg_count,
 					unsigned int *out_args);
+extern void syscon_register_phys_regmap_bus(struct regmap_bus *phy_regmap_bus);
 #else
 static inline struct regmap *device_node_to_regmap(struct device_node *np)
 {
@@ -59,6 +61,11 @@ static inline struct regmap *syscon_regmap_lookup_by_phandle_args(
 {
 	return ERR_PTR(-ENOTSUPP);
 }
+
+static inline void
+syscon_register_phys_regmap_bus(struct regmap_bus *phy_regmap_bus)
+{
+}
 #endif
 
 #endif /* __LINUX_MFD_SYSCON_H__ */
-- 
2.17.1

[PATCH 2/2] soc: sprd: Add Spreadtrum special bits updating support

[Baolin Wang]

The spreadtrum platform uses a special set/clear method to update
registers' bits, which can remove the race of updating the global
registers between the multiple subsystems. Thus we can register
a physical regmap bus into syscon core to support this.

Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
---
 drivers/soc/Kconfig            |  1 +
 drivers/soc/Makefile           |  1 +
 drivers/soc/sprd/Kconfig       | 16 +++++++
 drivers/soc/sprd/Makefile      |  2 +
 drivers/soc/sprd/sprd_syscon.c | 82 ++++++++++++++++++++++++++++++++++
 5 files changed, 102 insertions(+)
 create mode 100644 drivers/soc/sprd/Kconfig
 create mode 100644 drivers/soc/sprd/Makefile
 create mode 100644 drivers/soc/sprd/sprd_syscon.c

diff --git a/drivers/soc/Kconfig b/drivers/soc/Kconfig
index 425ab6f7e375..8cfbf2dc518d 100644
--- a/drivers/soc/Kconfig
+++ b/drivers/soc/Kconfig
@@ -23,5 +23,6 @@ source "drivers/soc/versatile/Kconfig"
 source "drivers/soc/xilinx/Kconfig"
 source "drivers/soc/zte/Kconfig"
 source "drivers/soc/kendryte/Kconfig"
+source "drivers/soc/sprd/Kconfig"
 
 endmenu
diff --git a/drivers/soc/Makefile b/drivers/soc/Makefile
index 36452bed86ef..7d156a6dd536 100644
--- a/drivers/soc/Makefile
+++ b/drivers/soc/Makefile
@@ -29,3 +29,4 @@ obj-$(CONFIG_PLAT_VERSATILE)	+= versatile/
 obj-y				+= xilinx/
 obj-$(CONFIG_ARCH_ZX)		+= zte/
 obj-$(CONFIG_SOC_KENDRYTE)	+= kendryte/
+obj-$(CONFIG_ARCH_SPRD)		+= sprd/
diff --git a/drivers/soc/sprd/Kconfig b/drivers/soc/sprd/Kconfig
new file mode 100644
index 000000000000..38d1f5971a28
--- /dev/null
+++ b/drivers/soc/sprd/Kconfig
@@ -0,0 +1,16 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# SPRD SoC drivers
+#
+
+menu "Spreadtrum SoC drivers"
+	depends on ARCH_SPRD || COMPILE_TEST
+
+config SPRD_SYSCON
+	tristate "Spreadtrum syscon support"
+	depends on ARCH_SPRD || COMPILE_TEST
+	help
+	  Say yes here to add support for the Spreadtrum syscon driver,
+	  which is used to implement the atomic method of bits updating.
+
+endmenu
diff --git a/drivers/soc/sprd/Makefile b/drivers/soc/sprd/Makefile
new file mode 100644
index 000000000000..4d7715553cf6
--- /dev/null
+++ b/drivers/soc/sprd/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_SPRD_SYSCON) += sprd_syscon.o
diff --git a/drivers/soc/sprd/sprd_syscon.c b/drivers/soc/sprd/sprd_syscon.c
new file mode 100644
index 000000000000..9b98127f1adb
--- /dev/null
+++ b/drivers/soc/sprd/sprd_syscon.c
@@ -0,0 +1,82 @@
+//SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Spreadtrum Communications Inc.
+ */
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
+
+#define SPRD_REG_SET_OFFSET	0x1000
+#define SPRD_REG_CLR_OFFSET	0x2000
+
+/*
+ * The Spreadtrum platform defines a special set/clear method to update
+ * registers' bits, which means it can write values to the register's SET
+ * address (offset is 0x1000) to set bits, and write values to the register's
+ * CLEAR address (offset is 0x2000) to clear bits.
+ *
+ * This set/clear method can help to remove the race of accessing the global
+ * registers between the multiple subsystems instead of using hardware
+ * spinlocks.
+ *
+ * Note: there is a potential risk when users want to set and clear bits
+ * at the same time, since the set/clear method will always do bits setting
+ * before bits clearing, which may cause some unexpected results if the
+ * operation sequence is strict. Thus we recommend that do not set and
+ * clear bits at the same time if you are not sure the results.
+ */
+static int sprd_syscon_update_bits(void *context, unsigned int reg,
+				   unsigned int mask, unsigned int val)
+{
+	void __iomem *base = context;
+	unsigned int set, clr;
+
+	set = val & mask;
+	clr = ~set & mask;
+
+	if (set)
+		writel(set, base + reg + SPRD_REG_SET_OFFSET);
+
+	if (clr)
+		writel(clr, base + reg + SPRD_REG_CLR_OFFSET);
+
+	return 0;
+}
+
+static int sprd_syscon_read(void *context, unsigned int reg, unsigned int *val)
+{
+	void __iomem *base = context;
+
+	*val = readl(base + reg);
+	return 0;
+}
+
+static int sprd_syscon_write(void *context, unsigned int reg, unsigned int val)
+{
+	void __iomem *base = context;
+
+	writel(val, base + reg);
+	return 0;
+}
+
+static struct regmap_bus sprd_syscon_regmap = {
+	.fast_io = true,
+	.reg_write = sprd_syscon_write,
+	.reg_read = sprd_syscon_read,
+	.reg_update_bits = sprd_syscon_update_bits,
+	.val_format_endian_default = REGMAP_ENDIAN_LITTLE,
+};
+
+static int sprd_syscon_init(void)
+{
+	syscon_register_phys_regmap_bus(&sprd_syscon_regmap);
+
+	return 0;
+}
+core_initcall_sync(sprd_syscon_init);
+
+MODULE_DESCRIPTION("Spreadtrum syscon support");
+MODULE_AUTHOR("Baolin Wang <baolin.wang@unisoc.com>");
+MODULE_LICENSE("GPL v2");
-- 
2.17.1

Re: [PATCH 2/2] soc: sprd: Add Spreadtrum special bits updating support

[Arnd Bergmann]

On Fri, Apr 17, 2020 at 4:14 AM Baolin Wang <baolin.wang7@gmail.com> wrote:
> + *
> + * Note: there is a potential risk when users want to set and clear bits
> + * at the same time, since the set/clear method will always do bits setting
> + * before bits clearing, which may cause some unexpected results if the
> + * operation sequence is strict. Thus we recommend that do not set and
> + * clear bits at the same time if you are not sure the results.

Would it make sense to have a

WARN_ONCE(set && clk, "%s: non-atomic update", __func__);

in the code to check for this?

> +static int sprd_syscon_init(void)
> +{
> +       syscon_register_phys_regmap_bus(&sprd_syscon_regmap);
> +
> +       return 0;
> +}
> +core_initcall_sync(sprd_syscon_init);

This no longer breaks at runtime based on the changes in the other
patch, but I still don't like how you have to manually load this module
on spreadtrum platforms.

What I meant to suggest in my previous reply was to add the regmap_bus
instance into drivers/mfd/syscon.c itself.

      Arnd

Re: [PATCH 2/2] soc: sprd: Add Spreadtrum special bits updating support

[Baolin Wang]

On Fri, Apr 17, 2020 at 9:39 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Fri, Apr 17, 2020 at 4:14 AM Baolin Wang <baolin.wang7@gmail.com> wrote:
> > + *
> > + * Note: there is a potential risk when users want to set and clear bits
> > + * at the same time, since the set/clear method will always do bits setting
> > + * before bits clearing, which may cause some unexpected results if the
> > + * operation sequence is strict. Thus we recommend that do not set and
> > + * clear bits at the same time if you are not sure the results.
>
> Would it make sense to have a
>
> WARN_ONCE(set && clk, "%s: non-atomic update", __func__);
>
> in the code to check for this?

Yes, will add.

>
> > +static int sprd_syscon_init(void)
> > +{
> > +       syscon_register_phys_regmap_bus(&sprd_syscon_regmap);
> > +
> > +       return 0;
> > +}
> > +core_initcall_sync(sprd_syscon_init);
>
> This no longer breaks at runtime based on the changes in the other
> patch, but I still don't like how you have to manually load this module
> on spreadtrum platforms.
>
> What I meant to suggest in my previous reply was to add the regmap_bus
> instance into drivers/mfd/syscon.c itself.

Sorry, I misunderstood your meaning before, but what you suggested
will add some vendor-specific things into the common syscon driver, if
other platforms have different update bits method, we will add another
vendor-specific regmap bus into the syscon.c, which will make syscon.c
more complicated.

But if you still prefer to add these vendor-specific things into the
syscon.c, I will follow your suggestion in next version. Thanks.

-- 
Baolin Wang

Re: [PATCH 2/2] soc: sprd: Add Spreadtrum special bits updating support

[Arnd Bergmann]

On Fri, Apr 17, 2020 at 4:10 PM Baolin Wang <baolin.wang7@gmail.com> wrote:
> On Fri, Apr 17, 2020 at 9:39 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > On Fri, Apr 17, 2020 at 4:14 AM Baolin Wang <baolin.wang7@gmail.com> wrote:
> > > +static int sprd_syscon_init(void)
> > > +{
> > > +       syscon_register_phys_regmap_bus(&sprd_syscon_regmap);
> > > +
> > > +       return 0;
> > > +}
> > > +core_initcall_sync(sprd_syscon_init);
> >
> > This no longer breaks at runtime based on the changes in the other
> > patch, but I still don't like how you have to manually load this module
> > on spreadtrum platforms.
> >
> > What I meant to suggest in my previous reply was to add the regmap_bus
> > instance into drivers/mfd/syscon.c itself.
>
> Sorry, I misunderstood your meaning before, but what you suggested
> will add some vendor-specific things into the common syscon driver, if
> other platforms have different update bits method, we will add another
> vendor-specific regmap bus into the syscon.c, which will make syscon.c
> more complicated.

I think we can always deal with this once it gets too complex, as long
as the DT binding allows it.

> But if you still prefer to add these vendor-specific things into the
> syscon.c, I will follow your suggestion in next version. Thanks.

Yes, please do.

       Arnd

Re: [PATCH 2/2] soc: sprd: Add Spreadtrum special bits updating support

[Baolin Wang]

On Fri, Apr 17, 2020 at 11:03 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Fri, Apr 17, 2020 at 4:10 PM Baolin Wang <baolin.wang7@gmail.com> wrote:
> > On Fri, Apr 17, 2020 at 9:39 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > > On Fri, Apr 17, 2020 at 4:14 AM Baolin Wang <baolin.wang7@gmail.com> wrote:
> > > > +static int sprd_syscon_init(void)
> > > > +{
> > > > +       syscon_register_phys_regmap_bus(&sprd_syscon_regmap);
> > > > +
> > > > +       return 0;
> > > > +}
> > > > +core_initcall_sync(sprd_syscon_init);
> > >
> > > This no longer breaks at runtime based on the changes in the other
> > > patch, but I still don't like how you have to manually load this module
> > > on spreadtrum platforms.
> > >
> > > What I meant to suggest in my previous reply was to add the regmap_bus
> > > instance into drivers/mfd/syscon.c itself.
> >
> > Sorry, I misunderstood your meaning before, but what you suggested
> > will add some vendor-specific things into the common syscon driver, if
> > other platforms have different update bits method, we will add another
> > vendor-specific regmap bus into the syscon.c, which will make syscon.c
> > more complicated.
>
> I think we can always deal with this once it gets too complex, as long
> as the DT binding allows it.
>
> > But if you still prefer to add these vendor-specific things into the
> > syscon.c, I will follow your suggestion in next version. Thanks.
>
> Yes, please do.

Sure. Thanks.

-- 
Baolin Wang

Re: [PATCH 1/2] mfd: syscon: Support physical regmap bus

[Lee Jones]

On Fri, 17 Apr 2020, Baolin Wang wrote:

> Some platforms such as Spreadtrum platform, define a special method to
> update bits of the registers instead of reading and writing, which means
> we should use a physical regmap bus to define the reg_update_bits()
> operation instead of the MMIO regmap bus.
> 
> Thus add a new helper for the syscon driver to allow to register a physical
> regmap bus to support this new requirement.
> 
> Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
> ---
>  drivers/mfd/syscon.c       | 23 +++++++++++++++++++++--
>  include/linux/mfd/syscon.h |  7 +++++++
>  2 files changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index 3a97816d0cba..92bfe87038ca 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -24,6 +24,7 @@
>  #include <linux/slab.h>
>  
>  static struct platform_driver syscon_driver;
> +static struct regmap_bus *syscon_phy_regmap_bus;
>  
>  static DEFINE_SPINLOCK(syscon_list_slock);
>  static LIST_HEAD(syscon_list);
> @@ -106,14 +107,25 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
>  	syscon_config.val_bits = reg_io_width * 8;
>  	syscon_config.max_register = resource_size(&res) - reg_io_width;
>  
> -	regmap = regmap_init_mmio(NULL, base, &syscon_config);
> +	 /*
> +	  * The Spreadtrum syscon need register a real physical regmap bus
> +	  * with new atomic bits updating operation instead of using
> +	  * read-modify-write.
> +	  */
> +	if (IS_ENABLED(CONFIG_ARCH_SPRD) &&
> +	    of_device_is_compatible(np, "sprd,atomic-syscon") &&

Please find a more generic way of supporting your use-case.  This is a
generic driver, and as such I am vehemently against adding any sort of
vendor specific code in here.

> +	    syscon_phy_regmap_bus)
> +		regmap = regmap_init(NULL, syscon_phy_regmap_bus, base,
> +				     &syscon_config);
> +	else
> +		regmap = regmap_init_mmio(NULL, base, &syscon_config);

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

Re: [PATCH 1/2] mfd: syscon: Support physical regmap bus

[Arnd Bergmann]

On Fri, Apr 24, 2020 at 10:11 AM Lee Jones <lee.jones@linaro.org> wrote:
> On Fri, 17 Apr 2020, Baolin Wang wrote:
> > @@ -106,14 +107,25 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
> >       syscon_config.val_bits = reg_io_width * 8;
> >       syscon_config.max_register = resource_size(&res) - reg_io_width;
> >
> > -     regmap = regmap_init_mmio(NULL, base, &syscon_config);
> > +      /*
> > +       * The Spreadtrum syscon need register a real physical regmap bus
> > +       * with new atomic bits updating operation instead of using
> > +       * read-modify-write.
> > +       */
> > +     if (IS_ENABLED(CONFIG_ARCH_SPRD) &&
> > +         of_device_is_compatible(np, "sprd,atomic-syscon") &&
>
> Please find a more generic way of supporting your use-case.  This is a
> generic driver, and as such I am vehemently against adding any sort of
> vendor specific code in here.

I suggested doing it this way, as all alternatives seemed worse than this.

        Arnd

Re: [PATCH 1/2] mfd: syscon: Support physical regmap bus

[Lee Jones]

On Fri, 24 Apr 2020, Arnd Bergmann wrote:

> On Fri, Apr 24, 2020 at 10:11 AM Lee Jones <lee.jones@linaro.org> wrote:
> > On Fri, 17 Apr 2020, Baolin Wang wrote:
> > > @@ -106,14 +107,25 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
> > >       syscon_config.val_bits = reg_io_width * 8;
> > >       syscon_config.max_register = resource_size(&res) - reg_io_width;
> > >
> > > -     regmap = regmap_init_mmio(NULL, base, &syscon_config);
> > > +      /*
> > > +       * The Spreadtrum syscon need register a real physical regmap bus
> > > +       * with new atomic bits updating operation instead of using
> > > +       * read-modify-write.
> > > +       */
> > > +     if (IS_ENABLED(CONFIG_ARCH_SPRD) &&
> > > +         of_device_is_compatible(np, "sprd,atomic-syscon") &&
> >
> > Please find a more generic way of supporting your use-case.  This is a
> > generic driver, and as such I am vehemently against adding any sort of
> > vendor specific code in here.
> 
> I suggested doing it this way, as all alternatives seemed worse than this.

If we're using a registration function (could probably be swapped out
for or accompanied by a Device Tree property) anyway, then why conduct
the vendor platform checks?

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

Re: [PATCH 1/2] mfd: syscon: Support physical regmap bus

[Baolin Wang]

On Fri, Apr 24, 2020 at 4:32 PM Lee Jones <lee.jones@linaro.org> wrote:
>
> On Fri, 24 Apr 2020, Arnd Bergmann wrote:
>
> > On Fri, Apr 24, 2020 at 10:11 AM Lee Jones <lee.jones@linaro.org> wrote:
> > > On Fri, 17 Apr 2020, Baolin Wang wrote:
> > > > @@ -106,14 +107,25 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
> > > >       syscon_config.val_bits = reg_io_width * 8;
> > > >       syscon_config.max_register = resource_size(&res) - reg_io_width;
> > > >
> > > > -     regmap = regmap_init_mmio(NULL, base, &syscon_config);
> > > > +      /*
> > > > +       * The Spreadtrum syscon need register a real physical regmap bus
> > > > +       * with new atomic bits updating operation instead of using
> > > > +       * read-modify-write.
> > > > +       */
> > > > +     if (IS_ENABLED(CONFIG_ARCH_SPRD) &&
> > > > +         of_device_is_compatible(np, "sprd,atomic-syscon") &&
> > >
> > > Please find a more generic way of supporting your use-case.  This is a
> > > generic driver, and as such I am vehemently against adding any sort of
> > > vendor specific code in here.
> >
> > I suggested doing it this way, as all alternatives seemed worse than this.
>
> If we're using a registration function (could probably be swapped out
> for or accompanied by a Device Tree property) anyway, then why conduct
> the vendor platform checks?

Actually I've send out the v3 patch according to Arnd's suggestion. In
v3 patch, I removed the registration function, but we agreed that
adding the vendor specific support in the syscon driver seems a better
way than others.

-- 
Baolin Wang

Re: [PATCH 1/2] mfd: syscon: Support physical regmap bus

[Baolin Wang]

On Fri, Apr 24, 2020 at 4:42 PM Baolin Wang <baolin.wang7@gmail.com> wrote:
>
> On Fri, Apr 24, 2020 at 4:32 PM Lee Jones <lee.jones@linaro.org> wrote:
> >
> > On Fri, 24 Apr 2020, Arnd Bergmann wrote:
> >
> > > On Fri, Apr 24, 2020 at 10:11 AM Lee Jones <lee.jones@linaro.org> wrote:
> > > > On Fri, 17 Apr 2020, Baolin Wang wrote:
> > > > > @@ -106,14 +107,25 @@ static struct syscon *of_syscon_register(struct device_node *np, bool check_clk)
> > > > >       syscon_config.val_bits = reg_io_width * 8;
> > > > >       syscon_config.max_register = resource_size(&res) - reg_io_width;
> > > > >
> > > > > -     regmap = regmap_init_mmio(NULL, base, &syscon_config);
> > > > > +      /*
> > > > > +       * The Spreadtrum syscon need register a real physical regmap bus
> > > > > +       * with new atomic bits updating operation instead of using
> > > > > +       * read-modify-write.
> > > > > +       */
> > > > > +     if (IS_ENABLED(CONFIG_ARCH_SPRD) &&
> > > > > +         of_device_is_compatible(np, "sprd,atomic-syscon") &&
> > > >
> > > > Please find a more generic way of supporting your use-case.  This is a
> > > > generic driver, and as such I am vehemently against adding any sort of
> > > > vendor specific code in here.
> > >
> > > I suggested doing it this way, as all alternatives seemed worse than this.
> >
> > If we're using a registration function (could probably be swapped out
> > for or accompanied by a Device Tree property) anyway, then why conduct
> > the vendor platform checks?
>
> Actually I've send out the v3 patch according to Arnd's suggestion. In
> v3 patch, I removed the registration function, but we agreed that
> adding the vendor specific support in the syscon driver seems a better
> way than others.

Sorry, I forgot the link:
https://lore.kernel.org/patchwork/patch/1228160/

-- 
Baolin Wang