On 08/02/2022 08:14, Tali Perry wrote:
>> -----Original Message-----
>> From: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxxxxx>
>> Sent: Monday, February 7, 2022 5:27 PM
>> To: Jonathan Neuschäfer <j.neuschaefer@xxxxxxx>; Tyrone Ting <warp5tw@xxxxxxxxx>
>> Cc: avifishman70@xxxxxxxxx; tmaimon77@xxxxxxxxx; tali.perry1@xxxxxxxxx; venture@xxxxxxxxxx; yuenn@xxxxxxxxxx; benjaminfair@xxxxxxxxxx; robh+dt@xxxxxxxxxx; semen.protsenko@xxxxxxxxxx; yangyicong@xxxxxxxxxxxxx; wsa@xxxxxxxxxx; jie.deng@xxxxxxxxx; sven@xxxxxxxxxxxxx; bence98@xxxxxxxxxx; lukas.bulwahn@xxxxxxxxx; arnd@xxxxxxxx; olof@xxxxxxxxx; andriy.shevchenko@xxxxxxxxxxxxxxx; IS20 Tali Perry <tali.perry@xxxxxxxxxxx>; IS20 Avi Fishman <Avi.Fishman@xxxxxxxxxxx>; IS20 Tomer Maimon <tomer.maimon@xxxxxxxxxxx>; CS20 KWLiu <KWLIU@xxxxxxxxxxx>; CS20 JJLiu0 <JJLIU0@xxxxxxxxxxx>; CS20 KFTing <KFTING@xxxxxxxxxxx>; devicetree@xxxxxxxxxxxxxxx; openbmc@xxxxxxxxxxxxxxxx; linux-i2c@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
>> Subject: Re: [PATCH v1 6/6] i2c: npcm: Support NPCM845
>>
>> On 07/02/2022 13:00, Jonathan Neuschäfer wrote:
>>> Hello,
>>>
>>> On Mon, Feb 07, 2022 at 02:33:38PM +0800, Tyrone Ting wrote:
>>>> From: Tyrone Ting <kfting@xxxxxxxxxxx>
>>>>
>>>> NPCM8XX uses a similar i2c module as NPCM7XX.
>>>> The only difference is that the internal HW FIFO is larger.
>>>>
>>>> Related Makefile and Kconfig files are modified to support as well.
>>>>
>>>> Fixes: 56a1485b102e ("i2c: npcm7xx: Add Nuvoton NPCM I2C controller
>>>> driver")
>>>
>>> It's not really a bug fix, but rather an additional feature.
>>> Therefore, I suggest removing the Fixes tag from this patch.
>>>
>>>> Signed-off-by: Tyrone Ting <kfting@xxxxxxxxxxx>
>>>> Signed-off-by: Tali Perry <tali.perry1@xxxxxxxxx>
>>>> ---
>>> [...]
>>>> /* init register and default value required to enable module */
>>>> #define NPCM_I2CSEGCTL 0xE4
>>>> +#ifdef CONFIG_ARCH_NPCM7XX
>>>> #define NPCM_I2CSEGCTL_INIT_VAL 0x0333F000
>>>> +#else
>>>> +#define NPCM_I2CSEGCTL_INIT_VAL 0x9333F000
>>>> +#endif
>>>
>>> This is going to cause problems when someone tries to compile a kernel
>>> that runs on both NPCM7xx and NPCM8xx (because the driver will then
>>> only work on NPCM7xx).
>>
>> Yes, good catch.
>>
>> The NPCM7XX is multiplatform, I guess NPCM8xx will be as well, so this looks like an invalid code. How such code is supposed to work on multiplatform kernel?
>>
>
> NPCM7xx and NPCM8xx are very different devices.
> They share same driver sources for some of the modules but it's not ABI.
> Users cannot compile a single kernel with two separate DTS.
> In case of the i2c controller, the npcm7xx has a 16 byte HW FIFO,
> and the NPCM8xx has 32 bytes HW FIFO.
> This also means that registers fields are slightly different.
> For init data we can move it to the DTS, but register field sizes
> can't be handled with this approach.
>
What do you mean they cannot compile a kernel with different DTS? Of
course they can - when we talk about multiplatform sub-architectures!
Maybe there is something specific in NPCMxxx which stops it but then it
should not be marked multiplatform.
Best regards,
Krzysztof
