On 2020-06-15 04:26, Lee Jones wrote:
> On Sun, 14 Jun 2020, Frank Rowand wrote:
>
>> Hi Lee,
>>
>> I'm looking at 5.8-rc1.
>>
>> The only use of OF_MFD_CELL() where the same compatible is specified
>> for multiple elements of a struct mfd_cell array is for compatible
>> "stericsson,ab8500-pwm" in drivers/mfd/ab8500-core.c:
>>
>> OF_MFD_CELL("ab8500-pwm",
>> NULL, NULL, 0, 1, "stericsson,ab8500-pwm"),
>> OF_MFD_CELL("ab8500-pwm",
>> NULL, NULL, 0, 2, "stericsson,ab8500-pwm"),
>> OF_MFD_CELL("ab8500-pwm",
>> NULL, NULL, 0, 3, "stericsson,ab8500-pwm"),
OF_MFD_CELL("ab8500-pwm",
NULL, NULL, 0, 0, "stericsson,ab8500-pwm"),
OF_MFD_CELL_REG("ab8500-pwm-mc",
NULL, NULL, 0, 0, "stericsson,ab8500-pwm", 0),
OF_MFD_CELL_REG("ab8500-pwm-mc",
NULL, NULL, 0, 1, "stericsson,ab8500-pwm", 1),
OF_MFD_CELL_REG("ab8500-pwm-mc",
NULL, NULL, 0, 2, "stericsson,ab8500-pwm", 2),
>>
>> The only .dts or .dtsi files where I see compatible "stericsson,ab8500-pwm"
>> are:
>>
>> arch/arm/boot/dts/ste-ab8500.dtsi
>> arch/arm/boot/dts/ste-ab8505.dtsi
>>
>> These two .dtsi files only have a single node with this compatible.
>> Chasing back to .dts and .dtsi files that include these two .dtsi
>> files, I see no case where there are multiple nodes with this
>> compatible.
>>
>> So it looks to me like there is no .dts in mainline that is providing
>> the three "stericsson,ab8500-pwm" nodes that drivers/mfd/ab8500-core.c
>> is expecting. No case that there are multiple mfd child nodes where
>> mfd_add_device() would assign the first of n child nodes with the
>> same compatible to multiple devices.
>>
>> So it appears to me that drivers/mfd/ab8500-core.c is currently broken.
>> Am I missing something here?
>>
>> If I am correct, then either drivers/mfd/ab8500-core.c or
>> ste-ab8500.dtsi and ste-ab8505.dtsi need to be fixed.
>
> Your analysis is correct.
OK, if I'm not overlooking anything, that is good news.
Existing .dts source files only have one "ab8500-pwm" child. They already
work correcly.
Create a new compatible for the case of multiple children. In my example
I will add "-mc" (multiple children) to the existing compatible. There
is likely a better name, but this lets me provide an example.
Modify drivers/mfd/ab8500-core.c to use the new compatible, and new .dts
source files with multiple children use the new compatible:
OF_MFD_CELL("ab8500-pwm",
NULL, NULL, 0, 0, "stericsson,ab8500-pwm"),
OF_MFD_CELL_REG("ab8500-pwm-mc",
NULL, NULL, 0, 0, "stericsson,ab8500-pwm", 0),
OF_MFD_CELL_REG("ab8500-pwm-mc",
NULL, NULL, 0, 1, "stericsson,ab8500-pwm", 1),
OF_MFD_CELL_REG("ab8500-pwm-mc",
NULL, NULL, 0, 2, "stericsson,ab8500-pwm", 2),
The "OF_MFD_CELL" entry is the existing entry, which will handle current
.dts source files. The new "OF_MFD_CELL_REG" entries will handle new
.dts source files.
And of course the patch that creates OF_MFD_CELL_REG() needs to precede
this change.
I would remove the fallback code in the existing patch that tries to
handle an incorrect binding. Just error out if the binding is not
used properly.
-Frank
>
> Although it's not "broken", it just works when it really shouldn't.
>
> I will be fixing the 'ab8500-pwm' case in due course.
>
>> Moving forward, your proposed OF_MFD_CELL_REG() method seems a good
>> approach (I have not completely read the actual code in the patch yet
>> though).
>
> Thanks.
>
