[PATCH v5 7/8] dt-binding: mtd: Document gpio-addr-flash

[PATCH v5 7/8] dt-binding: mtd: Document gpio-addr-flash

[Ricardo Ribalda Delgado]

Add documentation for gpio-addr-flash. This binding allow creating
flash devices that are paged using GPIOs.

Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
---
 .../bindings/mtd/gpio-addr-flash.txt          | 54 +++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt

diff --git a/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
new file mode 100644
index 000000000000..5006a26e1753
--- /dev/null
+++ b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
@@ -0,0 +1,54 @@
+Memory Mapped flash with some address lines addressed using GPIOs
+
+Handle the case where a flash device is mostly addressed using physical
+line and supplemented by GPIOs.  This way you can hook up say a 8MiB flash
+to a 2MiB memory range and use the GPIOs to select a particular range.
+
+ - compatible : "cfi-gpio-addr-flash"
+ - reg : Address range of the mtd chip that is memory mapped, this is,
+   on the previous example 2MiB.
+ - bank-width : Width (in bytes) of the bank.  Equal to the
+   device width times the number of interleaved chips.
+ - gpios: List of GPIO specifiers that will be used to address the MSBs address
+   lines. The order goes from LSB to MSB.
+ - probe-type : (optional) "cfi_probe", "jedec_probe". How the mtd chip
+   is going to be probed. If omitted, assumed to be equal to "cfi_probe".
+ - #address-cells, #size-cells : Must be present if the device has
+   sub-nodes representing partitions (see below).  In this case
+   both #address-cells and #size-cells must be equal to 1.
+
+The device tree may optionally contain sub-nodes describing partitions of the
+address space. Check partition.txt for more details.
+
+Example:
+
+	flash@300000 {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "cfi-gpio-addr-flash";
+		bank-width = <2>;
+		reg = < 0x00300000 0x00200000 >;
+		gpios = <&gpio_0 3 0>, <&gpio_0 4 0>;
+		partitions {
+			compatible = "fixed-partitions";
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			partition@0 {
+				reg = < 0x0 0x200000 >;
+				label = "Golden Bitstream";
+			};
+			partition@200000 {
+				reg = < 0x200000 0x200000 >;
+				label = "User Bitstream";
+			};
+			partition@400000 {
+				reg = < 0x400000 0x200000 >;
+				label = "V4L Controls";
+			};
+			partition@600000 {
+				reg = < 0x600000 0x200000 >;
+				label = "Production Data";
+			};
+		}
+	} ;
-- 
2.19.0

Re: [PATCH v5 7/8] dt-binding: mtd: Document gpio-addr-flash

[Boris Brezillon]

On Wed,  3 Oct 2018 21:38:58 +0200
Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com> wrote:

> Add documentation for gpio-addr-flash. This binding allow creating
> flash devices that are paged using GPIOs.
> 
> Cc: devicetree@vger.kernel.org
> Reviewed-by: Rob Herring <robh@kernel.org>
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
> ---
>  .../bindings/mtd/gpio-addr-flash.txt          | 54 +++++++++++++++++++
>  1 file changed, 54 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> 
> diff --git a/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> new file mode 100644
> index 000000000000..5006a26e1753
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> @@ -0,0 +1,54 @@
> +Memory Mapped flash with some address lines addressed using GPIOs
> +
> +Handle the case where a flash device is mostly addressed using physical
> +line and supplemented by GPIOs.  This way you can hook up say a 8MiB flash
> +to a 2MiB memory range and use the GPIOs to select a particular range.
> +
> + - compatible : "cfi-gpio-addr-flash"
> + - reg : Address range of the mtd chip that is memory mapped, this is,
> +   on the previous example 2MiB.
> + - bank-width : Width (in bytes) of the bank.  Equal to the
> +   device width times the number of interleaved chips.
> + - gpios: List of GPIO specifiers that will be used to address the MSBs address
> +   lines. The order goes from LSB to MSB.

I'd recommend naming the GPIO set (addr-gpios or msb-addr-gpios?), just
to make things clear.

> + - probe-type : (optional) "cfi_probe", "jedec_probe". How the mtd chip
> +   is going to be probed. If omitted, assumed to be equal to "cfi_probe".
> + - #address-cells, #size-cells : Must be present if the device has
> +   sub-nodes representing partitions (see below).  In this case
> +   both #address-cells and #size-cells must be equal to 1.
> +
> +The device tree may optionally contain sub-nodes describing partitions of the
> +address space. Check partition.txt for more details.
> +
> +Example:
> +
> +	flash@300000 {
> +		#address-cells = <1>;
> +		#size-cells = <1>;
> +		compatible = "cfi-gpio-addr-flash";
> +		bank-width = <2>;
> +		reg = < 0x00300000 0x00200000 >;
> +		gpios = <&gpio_0 3 0>, <&gpio_0 4 0>;
> +		partitions {
> +			compatible = "fixed-partitions";
> +			#address-cells = <1>;
> +			#size-cells = <1>;
> +
> +			partition@0 {
> +				reg = < 0x0 0x200000 >;
> +				label = "Golden Bitstream";
> +			};
> +			partition@200000 {
> +				reg = < 0x200000 0x200000 >;
> +				label = "User Bitstream";
> +			};
> +			partition@400000 {
> +				reg = < 0x400000 0x200000 >;
> +				label = "V4L Controls";
> +			};
> +			partition@600000 {
> +				reg = < 0x600000 0x200000 >;
> +				label = "Production Data";
> +			};
> +		}
> +	} ;

Re: [PATCH v5 7/8] dt-binding: mtd: Document gpio-addr-flash

[Boris Brezillon]

On Wed,  3 Oct 2018 21:38:58 +0200
Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com> wrote:

> Add documentation for gpio-addr-flash. This binding allow creating
> flash devices that are paged using GPIOs.
> 
> Cc: devicetree@vger.kernel.org
> Reviewed-by: Rob Herring <robh@kernel.org>
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
> ---
>  .../bindings/mtd/gpio-addr-flash.txt          | 54 +++++++++++++++++++
>  1 file changed, 54 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> 
> diff --git a/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> new file mode 100644
> index 000000000000..5006a26e1753
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> @@ -0,0 +1,54 @@
> +Memory Mapped flash with some address lines addressed using GPIOs
> +
> +Handle the case where a flash device is mostly addressed using physical
> +line and supplemented by GPIOs.  This way you can hook up say a 8MiB flash
> +to a 2MiB memory range and use the GPIOs to select a particular range.
> +
> + - compatible : "cfi-gpio-addr-flash"
> + - reg : Address range of the mtd chip that is memory mapped, this is,
> +   on the previous example 2MiB.
> + - bank-width : Width (in bytes) of the bank.  Equal to the
> +   device width times the number of interleaved chips.
> + - gpios: List of GPIO specifiers that will be used to address the MSBs address
> +   lines. The order goes from LSB to MSB.
> + - probe-type : (optional) "cfi_probe", "jedec_probe". How the mtd chip
> +   is going to be probed. If omitted, assumed to be equal to "cfi_probe".

Looks like other bindings are encoding the probe type in the
compatible [1][2], and we should probably follow what's been done by
others.

> + - #address-cells, #size-cells : Must be present if the device has
> +   sub-nodes representing partitions (see below).  In this case
> +   both #address-cells and #size-cells must be equal to 1.
> +
> +The device tree may optionally contain sub-nodes describing partitions of the
> +address space. Check partition.txt for more details.
> +
> +Example:
> +
> +	flash@300000 {
> +		#address-cells = <1>;
> +		#size-cells = <1>;

You should not have the #address-cells and #size-cells props defined at
this level, it's done in the partitions node already.

> +		compatible = "cfi-gpio-addr-flash";
> +		bank-width = <2>;
> +		reg = < 0x00300000 0x00200000 >;
> +		gpios = <&gpio_0 3 0>, <&gpio_0 4 0>;
> +		partitions {
> +			compatible = "fixed-partitions";
> +			#address-cells = <1>;
> +			#size-cells = <1>;
> +
> +			partition@0 {
> +				reg = < 0x0 0x200000 >;
> +				label = "Golden Bitstream";
> +			};
> +			partition@200000 {
> +				reg = < 0x200000 0x200000 >;
> +				label = "User Bitstream";
> +			};
> +			partition@400000 {
> +				reg = < 0x400000 0x200000 >;
> +				label = "V4L Controls";
> +			};
> +			partition@600000 {
> +				reg = < 0x600000 0x200000 >;
> +				label = "Production Data";
> +			};
> +		}
> +	} ;

[1]https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/mtd/cortina,gemini-flash.txt
[2]https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/mtd/arm-versatile.txt

Re: [PATCH v5 7/8] dt-binding: mtd: Document gpio-addr-flash

[Ricardo Ribalda Delgado]

Hi Boris
On Wed, Oct 3, 2018 at 11:27 PM Boris Brezillon
<boris.brezillon@bootlin.com> wrote:
>
> On Wed,  3 Oct 2018 21:38:58 +0200
> Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com> wrote:
>
> > Add documentation for gpio-addr-flash. This binding allow creating
> > flash devices that are paged using GPIOs.
> >
> > Cc: devicetree@vger.kernel.org
> > Reviewed-by: Rob Herring <robh@kernel.org>
> > Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
> > ---
> >  .../bindings/mtd/gpio-addr-flash.txt          | 54 +++++++++++++++++++
> >  1 file changed, 54 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> >
> > diff --git a/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> > new file mode 100644
> > index 000000000000..5006a26e1753
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> > @@ -0,0 +1,54 @@
> > +Memory Mapped flash with some address lines addressed using GPIOs
> > +
> > +Handle the case where a flash device is mostly addressed using physical
> > +line and supplemented by GPIOs.  This way you can hook up say a 8MiB flash
> > +to a 2MiB memory range and use the GPIOs to select a particular range.
> > +
> > + - compatible : "cfi-gpio-addr-flash"
> > + - reg : Address range of the mtd chip that is memory mapped, this is,
> > +   on the previous example 2MiB.
> > + - bank-width : Width (in bytes) of the bank.  Equal to the
> > +   device width times the number of interleaved chips.
> > + - gpios: List of GPIO specifiers that will be used to address the MSBs address
> > +   lines. The order goes from LSB to MSB.
> > + - probe-type : (optional) "cfi_probe", "jedec_probe". How the mtd chip
> > +   is going to be probed. If omitted, assumed to be equal to "cfi_probe".
>
> Looks like other bindings are encoding the probe type in the
> compatible [1][2], and we should probably follow what's been done by
> others.

If I understood it right, they are special cases of physmap_of_core.c
https://elixir.bootlin.com/linux/v4.18.11/source/drivers/mtd/maps/physmap_of_core.c#L242

The driver that handles the compatible is physmap_of_core.c, and afaik
multiple drivers with the same
compatible string is a very bad idea.

We can convert the driver to something like Versatile or gemini, but
then we will not support platform devices

btw, the binding that I am used is used by:
https://elixir.bootlin.com/linux/v4.18.11/source/drivers/mtd/maps/physmap_of_core.c#L91

Yes, I know is obsolete

Tomorrow morning I will try to address your comments, test in hw and resend

Thanks




>
> > + - #address-cells, #size-cells : Must be present if the device has
> > +   sub-nodes representing partitions (see below).  In this case
> > +   both #address-cells and #size-cells must be equal to 1.
> > +
> > +The device tree may optionally contain sub-nodes describing partitions of the
> > +address space. Check partition.txt for more details.
> > +
> > +Example:
> > +
> > +     flash@300000 {
> > +             #address-cells = <1>;
> > +             #size-cells = <1>;
>
> You should not have the #address-cells and #size-cells props defined at
> this level, it's done in the partitions node already.
>
> > +             compatible = "cfi-gpio-addr-flash";
> > +             bank-width = <2>;
> > +             reg = < 0x00300000 0x00200000 >;
> > +             gpios = <&gpio_0 3 0>, <&gpio_0 4 0>;
> > +             partitions {
> > +                     compatible = "fixed-partitions";
> > +                     #address-cells = <1>;
> > +                     #size-cells = <1>;
> > +
> > +                     partition@0 {
> > +                             reg = < 0x0 0x200000 >;
> > +                             label = "Golden Bitstream";
> > +                     };
> > +                     partition@200000 {
> > +                             reg = < 0x200000 0x200000 >;
> > +                             label = "User Bitstream";
> > +                     };
> > +                     partition@400000 {
> > +                             reg = < 0x400000 0x200000 >;
> > +                             label = "V4L Controls";
> > +                     };
> > +                     partition@600000 {
> > +                             reg = < 0x600000 0x200000 >;
> > +                             label = "Production Data";
> > +                     };
> > +             }
> > +     } ;
>
> [1]https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/mtd/cortina,gemini-flash.txt
> [2]https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/mtd/arm-versatile.txt



-- 
Ricardo Ribalda

Re: [PATCH v5 7/8] dt-binding: mtd: Document gpio-addr-flash

[Boris Brezillon]

On Wed, 3 Oct 2018 23:53:27 +0200
Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com> wrote:

> Hi Boris
> On Wed, Oct 3, 2018 at 11:27 PM Boris Brezillon
> <boris.brezillon@bootlin.com> wrote:
> >
> > On Wed,  3 Oct 2018 21:38:58 +0200
> > Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com> wrote:
> >  
> > > Add documentation for gpio-addr-flash. This binding allow creating
> > > flash devices that are paged using GPIOs.
> > >
> > > Cc: devicetree@vger.kernel.org
> > > Reviewed-by: Rob Herring <robh@kernel.org>
> > > Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
> > > ---
> > >  .../bindings/mtd/gpio-addr-flash.txt          | 54 +++++++++++++++++++
> > >  1 file changed, 54 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> > >
> > > diff --git a/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> > > new file mode 100644
> > > index 000000000000..5006a26e1753
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> > > @@ -0,0 +1,54 @@
> > > +Memory Mapped flash with some address lines addressed using GPIOs
> > > +
> > > +Handle the case where a flash device is mostly addressed using physical
> > > +line and supplemented by GPIOs.  This way you can hook up say a 8MiB flash
> > > +to a 2MiB memory range and use the GPIOs to select a particular range.
> > > +
> > > + - compatible : "cfi-gpio-addr-flash"
> > > + - reg : Address range of the mtd chip that is memory mapped, this is,
> > > +   on the previous example 2MiB.
> > > + - bank-width : Width (in bytes) of the bank.  Equal to the
> > > +   device width times the number of interleaved chips.
> > > + - gpios: List of GPIO specifiers that will be used to address the MSBs address
> > > +   lines. The order goes from LSB to MSB.
> > > + - probe-type : (optional) "cfi_probe", "jedec_probe". How the mtd chip
> > > +   is going to be probed. If omitted, assumed to be equal to "cfi_probe".  
> >
> > Looks like other bindings are encoding the probe type in the
> > compatible [1][2], and we should probably follow what's been done by
> > others.  
> 
> If I understood it right, they are special cases of physmap_of_core.c
> https://elixir.bootlin.com/linux/v4.18.11/source/drivers/mtd/maps/physmap_of_core.c#L242
> 
> The driver that handles the compatible is physmap_of_core.c, and afaik
> multiple drivers with the same
> compatible string is a very bad idea.

Yes, I know.

> 
> We can convert the driver to something like Versatile or gemini, but
> then we will not support platform devices
> 
> btw, the binding that I am used is used by:
> https://elixir.bootlin.com/linux/v4.18.11/source/drivers/mtd/maps/physmap_of_core.c#L91

Actually, the more I think about it the more I realize this should
somehow be integrated to the physmap core logic. I mean, there's nothing
controller/platform specific in what the gpio-physmap driver does.

We could basically add the msb_addr_gpios related fields to map_info,
let physmap.c and physmap_of_core.c call
devm_gpiod_get_array_optional() and, based on the returned value,
call simple_map_init() (when the pointer is NULL) or
gpio_addr_map_init() (when the pointer is valid).

gpio_addr_map_init() would still be implemented in gpio-addr-flash.c so
that we can still enable/disable support for this feature (providing
dummy wrappers when it's disabled). By doing that, we also keep a single
driver which matches a generic compatible string. We also stay
compatible with .c based board files.

Re: [PATCH v5 7/8] dt-binding: mtd: Document gpio-addr-flash

[Boris Brezillon]

On Thu, 4 Oct 2018 00:14:15 +0200
Boris Brezillon <boris.brezillon@bootlin.com> wrote:

> On Wed, 3 Oct 2018 23:53:27 +0200
> Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com> wrote:
> 
> > Hi Boris
> > On Wed, Oct 3, 2018 at 11:27 PM Boris Brezillon
> > <boris.brezillon@bootlin.com> wrote:  
> > >
> > > On Wed,  3 Oct 2018 21:38:58 +0200
> > > Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com> wrote:
> > >    
> > > > Add documentation for gpio-addr-flash. This binding allow creating
> > > > flash devices that are paged using GPIOs.
> > > >
> > > > Cc: devicetree@vger.kernel.org
> > > > Reviewed-by: Rob Herring <robh@kernel.org>
> > > > Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
> > > > ---
> > > >  .../bindings/mtd/gpio-addr-flash.txt          | 54 +++++++++++++++++++
> > > >  1 file changed, 54 insertions(+)
> > > >  create mode 100644 Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> > > > new file mode 100644
> > > > index 000000000000..5006a26e1753
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> > > > @@ -0,0 +1,54 @@
> > > > +Memory Mapped flash with some address lines addressed using GPIOs
> > > > +
> > > > +Handle the case where a flash device is mostly addressed using physical
> > > > +line and supplemented by GPIOs.  This way you can hook up say a 8MiB flash
> > > > +to a 2MiB memory range and use the GPIOs to select a particular range.
> > > > +
> > > > + - compatible : "cfi-gpio-addr-flash"
> > > > + - reg : Address range of the mtd chip that is memory mapped, this is,
> > > > +   on the previous example 2MiB.
> > > > + - bank-width : Width (in bytes) of the bank.  Equal to the
> > > > +   device width times the number of interleaved chips.
> > > > + - gpios: List of GPIO specifiers that will be used to address the MSBs address
> > > > +   lines. The order goes from LSB to MSB.
> > > > + - probe-type : (optional) "cfi_probe", "jedec_probe". How the mtd chip
> > > > +   is going to be probed. If omitted, assumed to be equal to "cfi_probe".    
> > >
> > > Looks like other bindings are encoding the probe type in the
> > > compatible [1][2], and we should probably follow what's been done by
> > > others.    
> > 
> > If I understood it right, they are special cases of physmap_of_core.c
> > https://elixir.bootlin.com/linux/v4.18.11/source/drivers/mtd/maps/physmap_of_core.c#L242
> > 
> > The driver that handles the compatible is physmap_of_core.c, and afaik
> > multiple drivers with the same
> > compatible string is a very bad idea.  
> 
> Yes, I know.
> 
> > 
> > We can convert the driver to something like Versatile or gemini, but
> > then we will not support platform devices
> > 
> > btw, the binding that I am used is used by:
> > https://elixir.bootlin.com/linux/v4.18.11/source/drivers/mtd/maps/physmap_of_core.c#L91  
> 
> Actually, the more I think about it the more I realize this should
> somehow be integrated to the physmap core logic. I mean, there's nothing
> controller/platform specific in what the gpio-physmap driver does.
> 
> We could basically add the msb_addr_gpios related fields to map_info,
> let physmap.c and physmap_of_core.c call
> devm_gpiod_get_array_optional() and, based on the returned value,
> call simple_map_init() (when the pointer is NULL) or
> gpio_addr_map_init() (when the pointer is valid).

Or even better, let simple_map_init() call gpio_addr_map_init() when
map->addr_gpios != NULL, so that you don't even have to duplicate the
selection logic in physmap.c and physmap_of_core.c.

> 
> gpio_addr_map_init() would still be implemented in gpio-addr-flash.c so
> that we can still enable/disable support for this feature (providing
> dummy wrappers when it's disabled). By doing that, we also keep a single
> driver which matches a generic compatible string. We also stay
> compatible with .c based board files.

Re: [PATCH v5 7/8] dt-binding: mtd: Document gpio-addr-flash

[Ricardo Ribalda Delgado]

HI Boris


On Thu, Oct 4, 2018 at 12:19 AM Boris Brezillon
<boris.brezillon@bootlin.com> wrote:
>
> On Thu, 4 Oct 2018 00:14:15 +0200
> Boris Brezillon <boris.brezillon@bootlin.com> wrote:
>
> > On Wed, 3 Oct 2018 23:53:27 +0200
> > Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com> wrote:
> >
> > > Hi Boris
> > > On Wed, Oct 3, 2018 at 11:27 PM Boris Brezillon
> > > <boris.brezillon@bootlin.com> wrote:
> > > >
> > > > On Wed,  3 Oct 2018 21:38:58 +0200
> > > > Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com> wrote:
> > > >
> > > > > Add documentation for gpio-addr-flash. This binding allow creating
> > > > > flash devices that are paged using GPIOs.
> > > > >
> > > > > Cc: devicetree@vger.kernel.org
> > > > > Reviewed-by: Rob Herring <robh@kernel.org>
> > > > > Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
> > > > > ---
> > > > >  .../bindings/mtd/gpio-addr-flash.txt          | 54 +++++++++++++++++++
> > > > >  1 file changed, 54 insertions(+)
> > > > >  create mode 100644 Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> > > > >
> > > > > diff --git a/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> > > > > new file mode 100644
> > > > > index 000000000000..5006a26e1753
> > > > > --- /dev/null
> > > > > +++ b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> > > > > @@ -0,0 +1,54 @@
> > > > > +Memory Mapped flash with some address lines addressed using GPIOs
> > > > > +
> > > > > +Handle the case where a flash device is mostly addressed using physical
> > > > > +line and supplemented by GPIOs.  This way you can hook up say a 8MiB flash
> > > > > +to a 2MiB memory range and use the GPIOs to select a particular range.
> > > > > +
> > > > > + - compatible : "cfi-gpio-addr-flash"
> > > > > + - reg : Address range of the mtd chip that is memory mapped, this is,
> > > > > +   on the previous example 2MiB.
> > > > > + - bank-width : Width (in bytes) of the bank.  Equal to the
> > > > > +   device width times the number of interleaved chips.
> > > > > + - gpios: List of GPIO specifiers that will be used to address the MSBs address
> > > > > +   lines. The order goes from LSB to MSB.
> > > > > + - probe-type : (optional) "cfi_probe", "jedec_probe". How the mtd chip
> > > > > +   is going to be probed. If omitted, assumed to be equal to "cfi_probe".
> > > >
> > > > Looks like other bindings are encoding the probe type in the
> > > > compatible [1][2], and we should probably follow what's been done by
> > > > others.
> > >
> > > If I understood it right, they are special cases of physmap_of_core.c
> > > https://elixir.bootlin.com/linux/v4.18.11/source/drivers/mtd/maps/physmap_of_core.c#L242
> > >
> > > The driver that handles the compatible is physmap_of_core.c, and afaik
> > > multiple drivers with the same
> > > compatible string is a very bad idea.
> >
> > Yes, I know.
> >
> > >
> > > We can convert the driver to something like Versatile or gemini, but
> > > then we will not support platform devices
> > >
> > > btw, the binding that I am used is used by:
> > > https://elixir.bootlin.com/linux/v4.18.11/source/drivers/mtd/maps/physmap_of_core.c#L91
> >
> > Actually, the more I think about it the more I realize this should
> > somehow be integrated to the physmap core logic. I mean, there's nothing
> > controller/platform specific in what the gpio-physmap driver does.
> >
> > We could basically add the msb_addr_gpios related fields to map_info,
> > let physmap.c and physmap_of_core.c call
> > devm_gpiod_get_array_optional() and, based on the returned value,
> > call simple_map_init() (when the pointer is NULL) or
> > gpio_addr_map_init() (when the pointer is valid).
>
> Or even better, let simple_map_init() call gpio_addr_map_init() when
> map->addr_gpios != NULL, so that you don't even have to duplicate the
> selection logic in physmap.c and physmap_of_core.c.
>

I am all in for the removal of duplicated code. But I have implemented
it slightly different, following gemini and versatile

In physmap_of_core.c

I have added

err = of_flash_probe_gpio(dev, dp, &info->list[i].map);
if (err){
iounmap(info->list[i].map.virt);
goto err_out;
}

and on gpio-addr-flash the code for DT is simply

int of_flash_probe_gpio(struct platform_device *pdev, struct device_node *np,
struct map_info *map)
{
struct async_state *state;

if (!of_device_is_compatible(np, "mtd,gpio-addr-flash"))
return 0;

state = devm_kzalloc(&pdev->dev, sizeof(*state), GFP_KERNEL);
if (!state)
return -ENOMEM;

return gpio_flash_probe_common(&pdev->dev, state, map);
}

You can take a look to the code at
https://github.com/ribalda/linux/tree/gpio-addr-flash-v6

once it is tested on hw I will commit to the list

I think now we are getting into something quite good :)

Thanks!

> >
> > gpio_addr_map_init() would still be implemented in gpio-addr-flash.c so
> > that we can still enable/disable support for this feature (providing
> > dummy wrappers when it's disabled). By doing that, we also keep a single
> > driver which matches a generic compatible string. We also stay
> > compatible with .c based board files.
>


-- 
Ricardo Ribalda