From: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
To: Tali Perry <tali.perry1@gmail.com>
Cc: "Tomer Maimon" <tmaimon77@gmail.com>,
devicetree <devicetree@vger.kernel.org>,
yangyicong@hisilicon.com, "Linux I2C" <linux-i2c@vger.kernel.org>,
"Benjamin Fair" <benjaminfair@google.com>,
"OpenBMC Maillist" <openbmc@lists.ozlabs.org>,
JJLIU0@nuvoton.com, lukas.bulwahn@gmail.com,
tomer.maimon@nuvoton.com, KWLIU@nuvoton.com, bence98@sch.bme.hu,
arnd@arndb.de, sven@svenpeter.dev,
"Jonathan Neuschäfer" <j.neuschaefer@gmx.net>,
"Rob Herring" <robh+dt@kernel.org>,
"Avi Fishman" <Avi.Fishman@nuvoton.com>,
"Tyrone Ting" <warp5tw@gmail.com>,
"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
semen.protsenko@linaro.org, jie.deng@intel.com,
avifishman70@gmail.com, "Patrick Venture" <venture@google.com>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Wolfram Sang" <wsa@kernel.org>,
kfting@nuvoton.com, "Tali Perry" <tali.perry@nuvoton.com>,
olof@lixom.net
Subject: Re: [PATCH v1 6/6] i2c: npcm: Support NPCM845
Date: Tue, 8 Feb 2022 09:56:45 +0100 [thread overview]
Message-ID: <1a172e64-f662-2a36-71ef-4214cfe5bffc@canonical.com> (raw)
In-Reply-To: <CAHb3i=ukzVr4DDgcPQ2+DO+LXWWtgjCe03WbG-CqvsOP_qqvUw@mail.gmail.com>
On 08/02/2022 09:51, Tali Perry wrote:
>> On 08/02/2022 08:14, Tali Perry wrote:
>>>> 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@nuvoton.com>
>>>>>>
>>>>>> 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@nuvoton.com>
>>>>>> Signed-off-by: Tali Perry <tali.perry1@gmail.com>
>>>>>> ---
>>>>> [...]
>>>>>> /* 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.
>>
>
>
> NCPM7xx is ARM32 bit (dual core Cortex A9)
> NPCM8xx is ARM64 bit (quad core Cortex A35)
>
> They have completely different architecture so not ABI compliant.
> I2C module is similar, but the devices are quite different and have
> separate architectures.
OK, in such case usually you indeed can't have both. :)
> Sorry for the confusion.
> This is the first patch we try to upstream for NPCM8xx.
> In the coming weeks we will upstream the architecture of NPCM8xx as well.
Still, ARCH_XXX should not be hard-coded in the drivers to change the
driver's behavior, even if driver won't be used simultaneously. It
breaks all design principles and prevents any further re-use if a new
use case appears.
You can use "ifdef ARCH_XXX" to skip building of some parts of the
driver, but it's not the case here.
Best regards,
Krzysztof
next prev parent reply other threads:[~2022-02-08 8:57 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-07 6:33 [PATCH v1 0/6] i2c: npcm: Bug fixes timeout, spurious interrupts Tyrone Ting
2022-02-07 6:33 ` [PATCH v1 1/6] dt-bindings: i2c: npcm: support NPCM845 Tyrone Ting
2022-02-07 11:21 ` Jonathan Neuschäfer
2022-02-07 11:27 ` Krzysztof Kozlowski
2022-02-07 14:22 ` Rob Herring
2022-02-08 8:44 ` warp5tw
2022-02-08 9:03 ` warp5tw
2022-02-11 16:14 ` Rob Herring
2022-02-12 3:19 ` warp5tw
2022-02-07 6:33 ` [PATCH v1 2/6] i2c: npcm: Fix timeout calculation Tyrone Ting
2022-02-07 11:21 ` Krzysztof Kozlowski
2022-02-07 11:27 ` Jonathan Neuschäfer
2022-02-08 9:09 ` warp5tw
2022-02-07 6:33 ` [PATCH v1 3/6] i2c: npcm: Add tx complete counter Tyrone Ting
2022-02-07 6:33 ` [PATCH v1 4/6] i2c: npcm: Handle spurious interrupts Tyrone Ting
2022-02-07 11:40 ` Jonathan Neuschäfer
2022-02-08 9:19 ` warp5tw
2022-02-07 6:33 ` [PATCH v1 5/6] i2c: npcm: Remove own slave addresses 2:10 Tyrone Ting
2022-02-07 6:33 ` [PATCH v1 6/6] i2c: npcm: Support NPCM845 Tyrone Ting
2022-02-07 12:00 ` Jonathan Neuschäfer
2022-02-07 15:26 ` Krzysztof Kozlowski
2022-02-08 7:11 ` tali.perry
2022-02-08 7:14 ` Tali Perry
2022-02-08 7:59 ` Krzysztof Kozlowski
2022-02-08 8:51 ` Tali Perry
2022-02-08 8:56 ` Krzysztof Kozlowski [this message]
2022-02-08 9:22 ` Tali Perry
2022-02-08 9:29 ` Krzysztof Kozlowski
2022-02-08 9:31 ` Avi Fishman
2022-02-08 9:39 ` Krzysztof Kozlowski
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