[PATCH 1/4] ARM: ep93xx: switch to SPARSEMEM

[alexander.sverdlin@gmail.com (Alexander Sverdlin)]

Hello Florian,

On 26/05/17 18:13, Florian Fainelli wrote:
>>> The EP93xx has four chip selects that can be used for the SDRAM memory.
>>> These chip selects are decoded to specify an address domain:
>>>
>>>   SDCS3  0x00000000-0x0fffffff with Boot Option ASDO=1
>>>   SDCS0  0xc0000000-0xcfffffff
>>>   SDCS1  0xd0000000-0xdfffffff
>>>   SDCS2  0xe0000000-x0efffffff
>>>   SDCS3  0xf0000000-0xffffffff with Boot Option ASDO=0
>>>
>>> Because of the row/column/bank architecture of SDRAM, the mapping of
>>> these memories into the processor's memory space is discontiguous.
>>>
>>> Most ep93xx systems only use one of the chip selects. For these systems,
>>> ARCH_HAS_HOLES_MEMORYMODEL has worked fine to handle the discontiguous
>>> memory.
>>>
>>> But, some of the TS-72xx boards use multiple chip selects. The TS-7300 in
>>> particular uses SDCS3 (with ASDO=1) and SDCS2. On that system with
>>> ARCH_HAS_HOLES_MEMORYMODEL the SDCS2 memory does not get handled correctly
>>> and results in the system not booting.
>>>
>>> Change the EP93xx to ARCH_SPARSEMEM_ENABLE. This handles the discontiguous
>>> memory for all configurations.
>>>
>>> This has been tested on the following ep93xx platforms:
>>>
>>> EDB9307A with 64 MiB on SDCS0
>>> Vision EP9307 with 64 MiB on SDCS0
>>> TS-7300 with 64 MiB on SDCS3 (with ASDO=1) and 64 MiB on SDCS2
>>> sim.one with 64 MiB on SDCS0
>>>
>>> Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
>>> Tested-by: Linus Walleij <linus.walleij@linaro.org>
>>> Cc: Russell King <linux@armlinux.org.uk>
>> Tested-by: Florian Fainelli <f.fainelli@gmail.com>
>>
>> On a TS-3700 with 32MiB of SDRAM, thanks!
>>
> OK this is weird, this patch applied against v4.11 works fine on a 32MB
> board configuration, but applied against v4.12-rc2 I now get the following:
> 
> Uncompressing Linux... done, booting the kernel.
> Warning: Neither atags nor dtb found
> 
> as if r2 was lost somehow.
> 
> I will start a bisection to figure out if/when it started to break.
> Russell do you have an idea?

I've applied the patch to 4.12-rc2 as well (to be more precise, 1b8f2ffc of Linus's tree),
and it boots fine on EDB9302 (32MiB one chip on SDCS3). I even ran "memtester" fine, one
iteration.

So, from my PoV
Tested-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>

--
Regards,
Alexander.