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[1/3] ARM: dts: Add headers with constants for MTD partitions

Message ID 1370962138-9631-2-git-send-email-florian.vaussard@epfl.ch (mailing list archive)
State New, archived
Headers show

Commit Message

Florian Vaussard June 11, 2013, 2:48 p.m. UTC 
These constants can be used to easily declare MTD partitions inside
DTS.

The constants MTDPART_OFS_* are purposely not included. Indeed,
parse_ofpart_partitions() is expecting u64, but a DT cell is u32.
Negative constants, as defined by MTDPART_OFS_*, would be wrongly
interpreted by parse_ofpart_partitions(). Two cells should be
used to correctly encode the negative constants, but this breaks
current usage.

Signed-off-by: Florian Vaussard <florian.vaussard@epfl.ch>
---
 include/dt-bindings/mtd/partitions.h |   12 ++++++++
 include/dt-bindings/sizes.h          |   52 ++++++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 0 deletions(-)
 create mode 100644 include/dt-bindings/mtd/partitions.h
 create mode 100644 include/dt-bindings/sizes.h

Comments

Stephen Warren June 11, 2013, 4:24 p.m. UTC | #1 
On 06/11/2013 08:48 AM, Florian Vaussard wrote:
> These constants can be used to easily declare MTD partitions inside
> DTS.
> 
> The constants MTDPART_OFS_* are purposely not included. Indeed,
> parse_ofpart_partitions() is expecting u64, but a DT cell is u32.
> Negative constants, as defined by MTDPART_OFS_*, would be wrongly
> interpreted by parse_ofpart_partitions(). Two cells should be
> used to correctly encode the negative constants, but this breaks
> current usage.

I think addition of common headers like this needs an ack from
Grant/Rob. I CC'd them here.

> diff --git a/include/dt-bindings/mtd/partitions.h b/include/dt-bindings/mtd/partitions.h

> + * This header provides constants used with MTD partitions.
...
> +/* Partition size */
> +#define MTDPART_SIZ_FULL	0

Which binding document in Documentation/devicetree/bindings is this
definition associated with? The comment above should really mention
this. Documentation/devicetree/bindings/mtd/partition.txt doesn't seem
to mention this value.

> diff --git a/include/dt-bindings/sizes.h b/include/dt-bindings/sizes.h

...
> +#define SZ_1G				0x40000000
> +#define SZ_2G				0x80000000
> +
> +#endif

For MTD partitions specifically, SZ_4G and onwards would be useful in
theory, although that would end up putting two cell values into a single
macro. and then the values couldn't be added/or'd together. So, I'm not
really sure if we want to add those larger values, but food for thought...
Florian Vaussard June 11, 2013, 5:28 p.m. UTC | #2 
Hello Stephen,

On 06/11/2013 06:24 PM, Stephen Warren wrote:
> On 06/11/2013 08:48 AM, Florian Vaussard wrote:
>> These constants can be used to easily declare MTD partitions inside
>> DTS.
>>
>> The constants MTDPART_OFS_* are purposely not included. Indeed,
>> parse_ofpart_partitions() is expecting u64, but a DT cell is u32.
>> Negative constants, as defined by MTDPART_OFS_*, would be wrongly
>> interpreted by parse_ofpart_partitions(). Two cells should be
>> used to correctly encode the negative constants, but this breaks
>> current usage.
>
> I think addition of common headers like this needs an ack from
> Grant/Rob. I CC'd them here.
>

Indeed. Thank you.

>> diff --git a/include/dt-bindings/mtd/partitions.h b/include/dt-bindings/mtd/partitions.h
>
>> + * This header provides constants used with MTD partitions.
> ...
>> +/* Partition size */
>> +#define MTDPART_SIZ_FULL	0
>
> Which binding document in Documentation/devicetree/bindings is this
> definition associated with? The comment above should really mention
> this. Documentation/devicetree/bindings/mtd/partition.txt doesn't seem
> to mention this value.
>

Mmmh I was not seeing this as a DT binding, strictly speaking. It was 
already
used with legacy board files. Otherwise we should also update the binding
for constants related to GPIO, IRQ,... But I agree that a line inside the
documentation never killed someone.

>> diff --git a/include/dt-bindings/sizes.h b/include/dt-bindings/sizes.h
>
> ...
>> +#define SZ_1G				0x40000000
>> +#define SZ_2G				0x80000000
>> +
>> +#endif
>
> For MTD partitions specifically, SZ_4G and onwards would be useful in
> theory, although that would end up putting two cell values into a single
> macro. and then the values couldn't be added/or'd together. So, I'm not
> really sure if we want to add those larger values, but food for thought...
>

It is maybe feasible to define a macro splitting the u64 into two
u32 cells? But this can be done afterwards when need arises.

Best regards,

Florian
Grant Likely June 12, 2013, 1:05 p.m. UTC | #3 
On Tue, 11 Jun 2013 16:48:56 +0200, Florian Vaussard <florian.vaussard@epfl.ch> wrote:
> These constants can be used to easily declare MTD partitions inside
> DTS.
> 
> The constants MTDPART_OFS_* are purposely not included. Indeed,
> parse_ofpart_partitions() is expecting u64, but a DT cell is u32.
> Negative constants, as defined by MTDPART_OFS_*, would be wrongly

The DT binding uses the number of cells defined by #address-cells. It is
not fixed to a u32 or a u64

> interpreted by parse_ofpart_partitions(). Two cells should be
> used to correctly encode the negative constants, but this breaks
> current usage.

The binding doesn't even allow for shortcuts like MTDPART_SIZ_FULL. If a
partition fills the whole device, then the reg property should include
the actual size. If the code is allowing '0' to be used to mean
MTDPART_SIZ_FULL, then that is a bug that needs to be fixed.

Please drop the mtd/partitions.h hunk from this patch.

g.

> 
> Signed-off-by: Florian Vaussard <florian.vaussard@epfl.ch>
> ---
>  include/dt-bindings/mtd/partitions.h |   12 ++++++++
>  include/dt-bindings/sizes.h          |   52 ++++++++++++++++++++++++++++++++++
>  2 files changed, 64 insertions(+), 0 deletions(-)
>  create mode 100644 include/dt-bindings/mtd/partitions.h
>  create mode 100644 include/dt-bindings/sizes.h
> 
> diff --git a/include/dt-bindings/mtd/partitions.h b/include/dt-bindings/mtd/partitions.h
> new file mode 100644
> index 0000000..7dfa676
> --- /dev/null
> +++ b/include/dt-bindings/mtd/partitions.h
> @@ -0,0 +1,12 @@
> +/*
> + * This header provides constants used with MTD partitions.
> + */
> +
> +#ifndef _DT_BINDINGS_MTD_PARTITIONS_H
> +#define _DT_BINDINGS_MTD_PARTITIONS_H
> +
> +/* Partition size */
> +#define MTDPART_SIZ_FULL	0
> +
> +#endif
> +
> diff --git a/include/dt-bindings/sizes.h b/include/dt-bindings/sizes.h
> new file mode 100644
> index 0000000..995f2de
> --- /dev/null
> +++ b/include/dt-bindings/sizes.h
> @@ -0,0 +1,52 @@
> +/*
> + * This header provides size constants.
> + *
> + * Original version:
> + *   include/linux/sizes.h
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#ifndef _DT_BINDINGS_SIZES_H
> +#define _DT_BINDINGS_SIZES_H
> +
> +#define SZ_1				0x00000001
> +#define SZ_2				0x00000002
> +#define SZ_4				0x00000004
> +#define SZ_8				0x00000008
> +#define SZ_16				0x00000010
> +#define SZ_32				0x00000020
> +#define SZ_64				0x00000040
> +#define SZ_128				0x00000080
> +#define SZ_256				0x00000100
> +#define SZ_512				0x00000200
> +
> +#define SZ_1K				0x00000400
> +#define SZ_2K				0x00000800
> +#define SZ_4K				0x00001000
> +#define SZ_8K				0x00002000
> +#define SZ_16K				0x00004000
> +#define SZ_32K				0x00008000
> +#define SZ_64K				0x00010000
> +#define SZ_128K				0x00020000
> +#define SZ_256K				0x00040000
> +#define SZ_512K				0x00080000
> +
> +#define SZ_1M				0x00100000
> +#define SZ_2M				0x00200000
> +#define SZ_4M				0x00400000
> +#define SZ_8M				0x00800000
> +#define SZ_16M				0x01000000
> +#define SZ_32M				0x02000000
> +#define SZ_64M				0x04000000
> +#define SZ_128M				0x08000000
> +#define SZ_256M				0x10000000
> +#define SZ_512M				0x20000000
> +
> +#define SZ_1G				0x40000000
> +#define SZ_2G				0x80000000
> +
> +#endif
> +
> -- 
> 1.7.5.4
> 
> _______________________________________________
> devicetree-discuss mailing list
> devicetree-discuss@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/devicetree-discuss
Florian Vaussard June 19, 2013, 9:19 a.m. UTC | #4 
Hello,

Thank you for the review.

On 06/12/2013 03:05 PM, Grant Likely wrote:
> On Tue, 11 Jun 2013 16:48:56 +0200, Florian Vaussard <florian.vaussard@epfl.ch> wrote:
>> These constants can be used to easily declare MTD partitions inside
>> DTS.
>>
>> The constants MTDPART_OFS_* are purposely not included. Indeed,
>> parse_ofpart_partitions() is expecting u64, but a DT cell is u32.
>> Negative constants, as defined by MTDPART_OFS_*, would be wrongly
>
> The DT binding uses the number of cells defined by #address-cells. It is
> not fixed to a u32 or a u64
>

The message was ill-formatted, sorry. As an address cell is u32, and as
parse_ofpart_partitions() is storing the value inside u64 without checking
for sign extension (as one assumes to have only positive offsets),
passing a negative value would require 2 address cells, making it more 
difficult
for the DT user. But as Stephen Warren noticed, it is probably desirable
to specify sizes >= 4GB, thus I will think about a way to easily handle 
such case.

Anyway, MTDPART_OFS_* would probably face the same objection raised by 
you for
MTDPART_SIZ_FULL.

>> interpreted by parse_ofpart_partitions(). Two cells should be
>> used to correctly encode the negative constants, but this breaks
>> current usage.
>
> The binding doesn't even allow for shortcuts like MTDPART_SIZ_FULL. If a
> partition fills the whole device, then the reg property should include
> the actual size. If the code is allowing '0' to be used to mean
> MTDPART_SIZ_FULL, then that is a bug that needs to be fixed.
>

The root problem is that many System on Module, like the Gumstix Overo, are
shipped with various NAND sizes depending on the version or even the 
manufacturing
period. Supporting such a diversity would painfully duplicates lots of DT
code and clutter the arch/arm/boot/dts/ directory with dozens of slightly-
different versions. I believe that determining the NAND size is better done
at probe time, and this is what is currently done in legacy board files:

static struct mtd_partition overo_nand_partitions[] = {
         {
                 .name           = "xloader",
                 .offset         = 0,                    /* Offset = 
0x00000 */
                 .size           = 4 * NAND_BLOCK_SIZE,
                 .mask_flags     = MTD_WRITEABLE
         },

<snip...>

         {
                 .name           = "rootfs",
                 .offset         = MTDPART_OFS_APPEND,   /* Offset = 
0x680000 */
                 .size           = MTDPART_SIZ_FULL,
         },
};

Moreover, I do not see such strict restriction in the OF norm. If I 
refer to IEEE
1275-1994 page 174, for the definition of the "reg" property, it is written:

"The interpretation of the size entries is dependent on the parent bus."

Nevertheless, if such an approach is not acceptable, could we think about an
alternative solution? Like a boolean property "mtd,append-and-fill" that 
would
replace the "reg" property and tell the MTD core to compute the 
partition size
at probe time, like what is currently done with board files?

Best regards,

Florian
diff mbox

Patch

diff --git a/include/dt-bindings/mtd/partitions.h b/include/dt-bindings/mtd/partitions.h
new file mode 100644
index 0000000..7dfa676
--- /dev/null
+++ b/include/dt-bindings/mtd/partitions.h
@@ -0,0 +1,12 @@ 
+/*
+ * This header provides constants used with MTD partitions.
+ */
+
+#ifndef _DT_BINDINGS_MTD_PARTITIONS_H
+#define _DT_BINDINGS_MTD_PARTITIONS_H
+
+/* Partition size */
+#define MTDPART_SIZ_FULL	0
+
+#endif
+
diff --git a/include/dt-bindings/sizes.h b/include/dt-bindings/sizes.h
new file mode 100644
index 0000000..995f2de
--- /dev/null
+++ b/include/dt-bindings/sizes.h
@@ -0,0 +1,52 @@ 
+/*
+ * This header provides size constants.
+ *
+ * Original version:
+ *   include/linux/sizes.h
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _DT_BINDINGS_SIZES_H
+#define _DT_BINDINGS_SIZES_H
+
+#define SZ_1				0x00000001
+#define SZ_2				0x00000002
+#define SZ_4				0x00000004
+#define SZ_8				0x00000008
+#define SZ_16				0x00000010
+#define SZ_32				0x00000020
+#define SZ_64				0x00000040
+#define SZ_128				0x00000080
+#define SZ_256				0x00000100
+#define SZ_512				0x00000200
+
+#define SZ_1K				0x00000400
+#define SZ_2K				0x00000800
+#define SZ_4K				0x00001000
+#define SZ_8K				0x00002000
+#define SZ_16K				0x00004000
+#define SZ_32K				0x00008000
+#define SZ_64K				0x00010000
+#define SZ_128K				0x00020000
+#define SZ_256K				0x00040000
+#define SZ_512K				0x00080000
+
+#define SZ_1M				0x00100000
+#define SZ_2M				0x00200000
+#define SZ_4M				0x00400000
+#define SZ_8M				0x00800000
+#define SZ_16M				0x01000000
+#define SZ_32M				0x02000000
+#define SZ_64M				0x04000000
+#define SZ_128M				0x08000000
+#define SZ_256M				0x10000000
+#define SZ_512M				0x20000000
+
+#define SZ_1G				0x40000000
+#define SZ_2G				0x80000000
+
+#endif
+