[RFC][PATCH 00/11] ARM: imx: Add initial i.MX28 support

[Shawn Guo]

Hi Sascha,

Thanks for the comments.  Please see my comments below.

On Tue, Nov 16, 2010 at 6:15 PM, Sascha Hauer <s.hauer at pengutronix.de> wrote:
> Hello Shawn,
>
> On Mon, Nov 15, 2010 at 10:36:24PM +0800, Shawn Guo wrote:
>> This patchset adds the initial support of i.MX28, and the target device
>> is i.MX28 EVK Rev C. It's based on the imx-single-kernel branch below,
>> and adding codes into arch/arm/mxc and arch/arm/mach-imx.
>
> Without further looking at the patch I agree with Uwe: The i.MX23/28
> are totally different from the other i.MX SoCs and should not be
> integrated in current i.MX support. And definitely it should not be
> integrated by adding cpu_is_* into each and every function.
>
cpu_is_* is not being added into each and every function. Uwe had this
comment on only two files, arch/arm/plat-mxc/gpio.c and
arch/arm/plat-mxc/time.c. As there are big percentage of
infrastructural common codes that are IP block independent, I though
it's good to use the same file.  But since you are not in this
position, I would propose another option. Like what I'm doing with
iomux-pinctrl, we can create arch/arm/plat-mxc/gpio-pinctrl.c and
arch/arm/plat-mxc/time-timrot.c for PINCTRL based gpio and TIMROT
based time implementation.

The philosophy behind this is we treat arch/arm/plat-mxc as the
Freescale IP block pool.  The driver in this folder is IP block
oriented other than SoC oriented.  And SoC is actually a collection of
IP blocks.  MX23/MX28 integrates PINCTRL, TIMROT, ICOLL, and
MX21/MX25/MX27/MX31/MX35/MX51 integrates GPIO/IOMUXC, GPT and
AVIC/TZIC.  Accordingly, MX23/MX28 builds gpio-pinctrl.c, timrot.c and
icoll.c in, and other i.MX builds gpio.c, iomux-v1//v2/v3,
avic.c/tzic.c in.  The only thing we need to deal with is picking up
the file name to stand for the IP block.

> Now you have two choices: Add the code to plat-stmp3xxx (for the
> interested reader: the i.MX23/28 are based on former Sigmatel SoCs), or
> add a new mach-mxs like you did in the Freescale Kernel.
> I'm not sure which choice of these two is best. It would be good to get
> some other opinions from people who already had the situation that a
> vendor got sold and we get the same old metal with new names.
>
Yes, MX23/28 are based on former Sigmatel SoCs.  The imx-single-kernel
demonstrates the possibility of single image for different SoCs from
same vendor.  My patchset somehow adds the the possibility for SoCs
even from different vendors, even though I'm unsure if single image
for SoCs from different vendor is something ARM Kernel will possibly
go in the future?

The plat-stmp3xxx is not an option for me because of the Freescale
marketing concern.  For the choice of what Freescale Kernel is doing,
there is no mach-mxs.  Instead, there are arch/arm/plat-mxs,
arch/arm/mach-mx23 and arch/arm/mach-mx28.  Going this way, MX23/28
will be totally separated from i.MX family, though their name tells
the relationship with i.MX family.  Also, Freescale is merging the
Sigmatel IP pool into i.MX one and will only maintain the same pool.
In another words, Sigmatel IP block are getting consolidated with i.MX
ones. You can still say MX28 are former Sigmatel based, but it gets
i.MX IP blocks, FEC(ENET), FlexCAN integrated.  If MX28 is not so
typical, MX50 can be the one.  It primarily derives from MX51/MX53 and
will go into plat-mxc and mach-mx5 in common understanding, but it
gets a lot of MX28 (Sigmatel) based IP blocks integrated, LCDIF, PXP,
GPMI, DCP, APHB DMA, and so on.  SoC is merging these two families
into one.  It makes no sense for SW to keeps them separated.

Can you please think about the IP oriented way I mentioned above to
see if there is any problem that stops us going?  Also do you want to
eventually include MX23/28 into imx-single-kernel image?  If you do,
don't you think my proposal will make it a little bit easier?

> BTW the imx-single-kernel branch is a branch to show where things might
> or might not go. You should not base your work on this.
>
> Sascha
>
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>



-- 
Regards,
Shawn