[U-Boot] [PATCH v2 0/4] ARM: imx: enhance support for the cm-fx6 module

[U-Boot] [PATCH v2 0/4] ARM: imx: enhance support for the cm-fx6 module

[christopher.spinrath at rwth-aachen.de]

Hi,

this is v2 of the series. To address the review comments of v1, v2 has an
addtional patch (2/4) touching include/fdt_support.h (thus, I added Simon
to the recipients).

The original cover letter was (for a discussion cf. [2]):

this series aims at enhancing support for the cm-fx6 module. In
particular, with respect to the upstream linux kernel.

The first patch improves the default environment. It is non-functional
but makes it more convenient to adapt certain settings.

The later two patches add mtd partition support for the on-board spi
flash chip. They pick up the discussion about specifying a default
partitioning in the device tree from here [1]. In short: adding the
default partitioning to the device tree was rejected by the linux/
device tree community during mainlining large parts of the device tree.
It was proposed to implement the partition/mtd handling in u-boot.
On the other hand, it was argued that the flash chip becomes some
kind of "black-box" since there will be no partition labeling (in
particular, with old u-boot versions).

IMHO defining the mtd partitioning has the following (dis-)advantages:

Advantages:
- It is easier for the user to change the partitioning (e.g. to use
  the unsued 1MB free space).

- The flash ship is used entirely for u-boot. So it is quite natural
  that u-boot manages it. Also, moving the partition table to it
  allows us to change the layout in future versions of u-boot (almost
  independently of the kernel - there are still non-device tree kernels).

- U-Boot becomes the single point of definition for all device tree
  kernels. Otherwise, each kernel (vendor vs. upstream + version)
  would ship its own partitioning. Moreover, u-boot has to know
  something about the partitioning, too, because it has to know where
  the environment is saved.

Disadvantages:
- Users of the upstream linux kernel have to use a recent u-boot
  version to avoid the "black box" effect. A concrete impact is
  that the update routine (described/proposed by CompuLab) does
  not work out of the box with older u-boot versions.

- Updating u-boot is something users might not want or miss to do.

However, I think nowadays it is ok to demand a recent u-boot in
combination with the upstream kernel. The cm-fx6 wouldn't be
the first board doing so. Hence, I propose these patches here.

Cheers,
Christopher

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-June/434562.html
[2] http://lists.denx.de/pipermail/u-boot/2016-June/258546.html

[U-Boot] [PATCH v2 0/4] ARM: imx: enhance support for the cm-fx6 module

[Nikita Kiryanov]

Hi Christopher, Stefano,

Whole series:
Acked-by: Nikita Kiryanov <nikita@compulab.co.il>

On Tue, Jul 12, 2016 at 11:37:33PM +0200, christopher.spinrath at rwth-aachen.de wrote:
> Hi,
> 
> this is v2 of the series. To address the review comments of v1, v2 has an
> addtional patch (2/4) touching include/fdt_support.h (thus, I added Simon
> to the recipients).
> 
> The original cover letter was (for a discussion cf. [2]):
> 
> this series aims at enhancing support for the cm-fx6 module. In
> particular, with respect to the upstream linux kernel.
> 
> The first patch improves the default environment. It is non-functional
> but makes it more convenient to adapt certain settings.
> 
> The later two patches add mtd partition support for the on-board spi
> flash chip. They pick up the discussion about specifying a default
> partitioning in the device tree from here [1]. In short: adding the
> default partitioning to the device tree was rejected by the linux/
> device tree community during mainlining large parts of the device tree.
> It was proposed to implement the partition/mtd handling in u-boot.
> On the other hand, it was argued that the flash chip becomes some
> kind of "black-box" since there will be no partition labeling (in
> particular, with old u-boot versions).
> 
> IMHO defining the mtd partitioning has the following (dis-)advantages:
> 
> Advantages:
> - It is easier for the user to change the partitioning (e.g. to use
>   the unsued 1MB free space).
> 
> - The flash ship is used entirely for u-boot. So it is quite natural
>   that u-boot manages it. Also, moving the partition table to it
>   allows us to change the layout in future versions of u-boot (almost
>   independently of the kernel - there are still non-device tree kernels).
> 
> - U-Boot becomes the single point of definition for all device tree
>   kernels. Otherwise, each kernel (vendor vs. upstream + version)
>   would ship its own partitioning. Moreover, u-boot has to know
>   something about the partitioning, too, because it has to know where
>   the environment is saved.
> 
> Disadvantages:
> - Users of the upstream linux kernel have to use a recent u-boot
>   version to avoid the "black box" effect. A concrete impact is
>   that the update routine (described/proposed by CompuLab) does
>   not work out of the box with older u-boot versions.
> 
> - Updating u-boot is something users might not want or miss to do.
> 
> However, I think nowadays it is ok to demand a recent u-boot in
> combination with the upstream kernel. The cm-fx6 wouldn't be
> the first board doing so. Hence, I propose these patches here.
> 
> Cheers,
> Christopher
> 
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-June/434562.html
> [2] http://lists.denx.de/pipermail/u-boot/2016-June/258546.html
>