[PATCH v3 14/36] mtd: st_spi_fsm: Add device-tree binding documentation

[PATCH v3 14/36] mtd: st_spi_fsm: Add device-tree binding documentation

[Lee Jones]

Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Signed-off-by: Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
 Documentation/devicetree/bindings/mtd/st-fsm.txt | 26 ++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mtd/st-fsm.txt

diff --git a/Documentation/devicetree/bindings/mtd/st-fsm.txt b/Documentation/devicetree/bindings/mtd/st-fsm.txt
new file mode 100644
index 0000000..c248939
--- /dev/null
+++ b/Documentation/devicetree/bindings/mtd/st-fsm.txt
@@ -0,0 +1,26 @@
+* ST-Microelectronics SPI FSM Serial (NOR) Flash Controller
+
+Required properties:
+  - compatible : Should be "st,spi-fsm"
+  - reg        : Contains register's location and length.
+  - reg-names  : Should contain the reg names "spi-fsm"
+  - interrupts : The interrupt number
+  - pinctrl-0  : Standard Pinctrl phandle (see: pinctrl/pinctrl-bindings.txt)
+
+Optional properties:
+  - st,syscfg          : Phandle to boot-device system configuration registers
+  - st,boot-device-reg : Address of the aforementioned boot-device register(s)
+  - st,boot-device-spi : Expected boot-device value if booted via this device
+
+Example:
+	spifsm: spifsm@fe902000{
+	        compatible         = "st,spi-fsm";
+	        reg                =  <0xfe902000 0x1000>;
+	        reg-names          = "spi-fsm";
+	        pinctrl-0          = <&pinctrl_fsm>;
+		st,syscfg	   = <&syscfg_rear>;
+	        st,boot-device-reg = <0x958>;
+	        st,boot-device-spi = <0x1a>;
+		status = "okay";
+	};
+
-- 
1.8.3.2

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Re: [PATCH v3 14/36] mtd: st_spi_fsm: Add device-tree binding documentation

[Linus Walleij]

On Fri, Nov 29, 2013 at 1:19 PM, Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:

Re this:

> +Optional properties:
> +  - st,syscfg          : Phandle to boot-device system configuration registers
> +  - st,boot-device-reg : Address of the aforementioned boot-device register(s)
> +  - st,boot-device-spi : Expected boot-device value if booted via this device
> +
> +Example:
> +       spifsm: spifsm@fe902000{
> +               compatible         = "st,spi-fsm";
> +               reg                =  <0xfe902000 0x1000>;
> +               reg-names          = "spi-fsm";
> +               pinctrl-0          = <&pinctrl_fsm>;
> +               st,syscfg          = <&syscfg_rear>;
> +               st,boot-device-reg = <0x958>;
> +               st,boot-device-spi = <0x1a>;

I don't think we should encode any register offsets whatsoever in device
tree but maybe that's just me. (Yes, Stephen will beat me up about
pin control single, but I consider that a special case.)

I would just put the last two things as #defines into the driver file(s)
or - if it's related to other syscfg registers and varies with SoC incarnation,
as a #define in a shared header for that syscfg thing.

The syscfg phandle is elegant though, really like that.

Yours,
Linus Walleij
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Re: [PATCH v3 14/36] mtd: st_spi_fsm: Add device-tree binding documentation

[Lee Jones]

> > +Optional properties:
> > +  - st,syscfg          : Phandle to boot-device system configuration registers
> > +  - st,boot-device-reg : Address of the aforementioned boot-device register(s)
> > +  - st,boot-device-spi : Expected boot-device value if booted via this device
> > +
> > +Example:
> > +       spifsm: spifsm@fe902000{
> > +               compatible         = "st,spi-fsm";
> > +               reg                =  <0xfe902000 0x1000>;
> > +               reg-names          = "spi-fsm";
> > +               pinctrl-0          = <&pinctrl_fsm>;
> > +               st,syscfg          = <&syscfg_rear>;
> > +               st,boot-device-reg = <0x958>;
> > +               st,boot-device-spi = <0x1a>;
> 
> I don't think we should encode any register offsets whatsoever in device
> tree but maybe that's just me. (Yes, Stephen will beat me up about
> pin control single, but I consider that a special case.)
> 
> I would just put the last two things as #defines into the driver file(s)
> or - if it's related to other syscfg registers and varies with SoC incarnation,
> as a #define in a shared header for that syscfg thing.

No can do. This isn't _this_ device's register offset, this is a
syscfg register offset which a) there is no driver to apply specific
register offsets to and b) are liable to change oversubsequent SoCs.

> The syscfg phandle is elegant though, really like that.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

Re: [PATCH v3 14/36] mtd: st_spi_fsm: Add device-tree binding documentation

[Linus Walleij]

On Mon, Dec 2, 2013 at 12:03 PM, Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:
>> > +Optional properties:
>> > +  - st,syscfg          : Phandle to boot-device system configuration registers
>> > +  - st,boot-device-reg : Address of the aforementioned boot-device register(s)
>> > +  - st,boot-device-spi : Expected boot-device value if booted via this device
>> > +
>> > +Example:
>> > +       spifsm: spifsm@fe902000{
>> > +               compatible         = "st,spi-fsm";
>> > +               reg                =  <0xfe902000 0x1000>;
>> > +               reg-names          = "spi-fsm";
>> > +               pinctrl-0          = <&pinctrl_fsm>;
>> > +               st,syscfg          = <&syscfg_rear>;
>> > +               st,boot-device-reg = <0x958>;
>> > +               st,boot-device-spi = <0x1a>;
>>
>> I don't think we should encode any register offsets whatsoever in device
>> tree but maybe that's just me. (Yes, Stephen will beat me up about
>> pin control single, but I consider that a special case.)
>>
>> I would just put the last two things as #defines into the driver file(s)
>> or - if it's related to other syscfg registers and varies with SoC incarnation,
>> as a #define in a shared header for that syscfg thing.
>
> No can do. This isn't _this_ device's register offset, this is a
> syscfg register offset which a) there is no driver to apply specific
> register offsets to and b) are liable to change oversubsequent SoCs.

So it can be in <linux/mfd/my-sysconfig-regs.h> as
a

#define MY_SYSCON_V1_BOOT_DEV_REG 0x958
#define MY_SYSCON_V1_BOOT_DEV_SPI 0x1a

The kernel should know which SoC is in use and
act apropriately right?

But indeed, what you're doing has been done before
in drivers/regulator/anatop-regulator.c where some
register offset is read in from the attribute
"anatop-delay-reg-offset". So it may be that the DT people
need to overrule me on this one :-)

I don't think we should hard-code knowledge of specific
register locations into the device tree at all as that makes
things very hard to debug.

Yours,
Linus Walleij
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Re: [PATCH v3 14/36] mtd: st_spi_fsm: Add device-tree binding documentation

[Lee Jones]

On Tue, 03 Dec 2013, Linus Walleij wrote:

> On Mon, Dec 2, 2013 at 12:03 PM, Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:
> >> > +Optional properties:
> >> > +  - st,syscfg          : Phandle to boot-device system configuration registers
> >> > +  - st,boot-device-reg : Address of the aforementioned boot-device register(s)
> >> > +  - st,boot-device-spi : Expected boot-device value if booted via this device
> >> > +
> >> > +Example:
> >> > +       spifsm: spifsm@fe902000{
> >> > +               compatible         = "st,spi-fsm";
> >> > +               reg                =  <0xfe902000 0x1000>;
> >> > +               reg-names          = "spi-fsm";
> >> > +               pinctrl-0          = <&pinctrl_fsm>;
> >> > +               st,syscfg          = <&syscfg_rear>;
> >> > +               st,boot-device-reg = <0x958>;
> >> > +               st,boot-device-spi = <0x1a>;
> >>
> >> I don't think we should encode any register offsets whatsoever in device
> >> tree but maybe that's just me. (Yes, Stephen will beat me up about
> >> pin control single, but I consider that a special case.)
> >>
> >> I would just put the last two things as #defines into the driver file(s)
> >> or - if it's related to other syscfg registers and varies with SoC incarnation,
> >> as a #define in a shared header for that syscfg thing.
> >
> > No can do. This isn't _this_ device's register offset, this is a
> > syscfg register offset which a) there is no driver to apply specific
> > register offsets to and b) are liable to change oversubsequent SoCs.
> 
> So it can be in <linux/mfd/my-sysconfig-regs.h> as
> a
> 
> #define MY_SYSCON_V1_BOOT_DEV_REG 0x958
> #define MY_SYSCON_V1_BOOT_DEV_SPI 0x1a
> 
> The kernel should know which SoC is in use and
> act apropriately right?

And this have lots of machine_is() calls everywhere?

Sounds perfect. ;)

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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Re: [PATCH v3 14/36] mtd: st_spi_fsm: Add device-tree binding documentation

[Linus Walleij]

On Tue, Dec 3, 2013 at 12:31 PM, Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:
> On Tue, 03 Dec 2013, Linus Walleij wrote:

>> So it can be in <linux/mfd/my-sysconfig-regs.h> as
>> a
>>
>> #define MY_SYSCON_V1_BOOT_DEV_REG 0x958
>> #define MY_SYSCON_V1_BOOT_DEV_SPI 0x1a
>>
>> The kernel should know which SoC is in use and
>> act apropriately right?
>
> And this have lots of machine_is() calls everywhere?

No need for Mr. Everywhere to know about the SoC.

There are other ways to achieve this. arch/arm/mach-foo
always knows which ASIC it is running on, and it can do
various things:

- Add device tree fragments/overlays (OK high-tech, but
  we're getting to this, inevitably)

- Selectively add AUXDATA, which is absolutely OK if
  we can do autoprobing of hardware IMO.

Yours,
Linus Walleij
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Re: [PATCH v3 14/36] mtd: st_spi_fsm: Add device-tree binding documentation

[Lee Jones]

On Tue, 03 Dec 2013, Linus Walleij wrote:

> On Tue, Dec 3, 2013 at 12:31 PM, Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:
> > On Tue, 03 Dec 2013, Linus Walleij wrote:
> 
> >> So it can be in <linux/mfd/my-sysconfig-regs.h> as
> >> a
> >>
> >> #define MY_SYSCON_V1_BOOT_DEV_REG 0x958
> >> #define MY_SYSCON_V1_BOOT_DEV_SPI 0x1a
> >>
> >> The kernel should know which SoC is in use and
> >> act apropriately right?
> >
> > And this have lots of machine_is() calls everywhere?
> 
> No need for Mr. Everywhere to know about the SoC.
> 
> There are other ways to achieve this. arch/arm/mach-foo
> always knows which ASIC it is running on, and it can do
> various things:
> 
> - Add device tree fragments/overlays (OK high-tech, but
>   we're getting to this, inevitably)
> 
> - Selectively add AUXDATA, which is absolutely OK if
>   we can do autoprobing of hardware IMO.

I prefer our solution TBH.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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