Hi Dirk,
On Wed, Jun 1, 2016 at 9:19 AM, Dirk Behme <dirk.be...@de.bosch.com> wrote:
> On 01.06.2016 07:19, Magnus Damm wrote:
>> On Fri, May 27, 2016 at 4:56 PM, Dirk Behme <dirk.be...@de.bosch.com>
>> wrote:
>>> On 27.05.2016 05:13, Magnus Damm wrote:
>>>> I don't think anyone disagrees that it makes sense to be able to
>>>> determine ES version during runtime. The questions in my mind are how
>>>> to do it
>>>
>>> I've made a proposal ;) And I'm happy to discuss technically about it.
>>
>> Thanks! It would be interesting to know the reason behind your
>> interest in these things. For instance, if you are interested in
>> reducing run time memory usage, or general source code duplication
>> reduction. Do you have any target platform that you can upstream board
>> support for?
>>
>>>> and the urgency.
>>>
>>> Regarding the urgency: Someone has accepted the hard coded PRODUCT
>>> register
>>> (and MODEMR) being in renesas-drivers, now:
>>>
>>> https://git.kernel.org/cgit/linux/kernel/git/geert/renesas-drivers.git/tree/drivers/gpu/drm/rcar-du/rcar_du_crtc.c?h=topic/gen3-latest#n177
>>>
>>> This does really hurts us.
>>>
>>> Therefore, I try to get this removed as soon as possible to hopefully get
>>> a
>>> Renesas BSP without this, the next time.
>>>
>>> If anybody finds an other way to remove that, that would be fine, too.
>>
>> Please share the underlying issue so we can fix that.
>>
>>>> So far we have decided to use the compatible string since it is a
>>>> common driver model abstraction already used by device drivers and
>>>> hardware description in DT. Using DT compat string matching we can
>>>> have logic in the drivers to handle ES differences if needed. As for
>>>> how to enable the workaround, my opinion is that the missing piece
>>>> consists of ES workaround code that appends ES suffix information to
>>>> the DT compat strings automatically during boot.
>>>
>>> Technically this sounds slightly too complicated to me. As I have to
>>> advocate my proposal (inspired from an other mainline SoC family) I'd
>>> think
>>> that my proposal is easier.
>>
>> It may indeed be easier in the short term, but I feel we need to
>> consider how to support a wide range of SoCs in a consistent way.
>>
>>>> I suppose the workaround is not yet implemented because no one has
>>>> deemed this topic as particularly urgent. Until it becomes urgent or a
>>>> new ES version appears the affected users can simply adjust the DT
>>>> binding themselves. This is what happened to the "sata-r8a7790-es1"
>>>> case above.
>>
>> Can you see any technical reason why using DT compat strings wouldn't
>> solve your case?
>
> I'll try to explain my understanding. Please re-ask or correct me if I fail
> ;)
>
> First of all, I can talk only about R-Car3. There, at the moment, we have
> ES1, ES2 and ES3 documented, already. We don't know, yet, if these are
> really needed in the code, but it might be.
>
> Taking the example above, we then would have
>
> compatible = "renesas,sata-r8a7790", "sata-r8a7790-es1", "sata-r8a7790-es2",
> "sata-r8a7790-es3";
>
> in the device tree. Do we want that? No! Because its no run time detection.
You would only have "renesas,sata-r8a7790" for normal parts.
ES1 needs "renesas,sata-r8a7790-es1".
"esX" compatible values are the exception, not the rule.
> If we don't want that, and we want runtime detection, I think anywhere in
> this thread it was mentioned that the "es1" string is appended to
> sata-r8a7790 at runtime? If so, could you point us to the code for that?
The PoC is on my local SSD. Will send out soon.
> Then we have anything like
>
> if(PRODUCT_REG & ES1 == ES1)
> append ES1 to the compatible string
>
> in the boot code. This is one additional indirection to my proposal, needing
> boot time. In the driver you then add
>
> {
> .compatible = "renesas,sata-r8a7790-es1",
> .data = (void *)RCAR_R8A7790_ES1_SATA
> },
> {
> .compatible = "renesas,sata-r8a7790-es2",
> .data = (void *)RCAR_R8A7790_ES2_SATA
> },
> {
> .compatible = "renesas,sata-r8a7790-es3",
> .data = (void *)RCAR_R8A7790_ES3_SATA
> },
No, only "renesas,sata-r8a7790" and "renesas,sata-r8a7790-es1", like we
already have.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
