[PATCH] drm: bridge: cdns-mhdp8546: fix compile warning

[Tomi Valkeinen]

On 25/09/2020 15:00, Laurent Pinchart wrote:
> On Fri, Sep 25, 2020 at 10:36:44AM +0300, Tomi Valkeinen wrote:
>> On 24/09/2020 14:48, Laurent Pinchart wrote:
>>> Hi Tomi,
>>>
>>> Thank you for the patch.
>>>
>>> On Wed, Sep 23, 2020 at 11:30:57AM +0300, Tomi Valkeinen wrote:
>>>> On x64 we get:
>>>>
>>>> drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c:751:10: warning: conversion from 'long unsigned int' to 'unsigned int' changes value from '18446744073709551613' to '4294967293' [-Woverflow]
>>>>
>>>> The registers are 32 bit, so fix by casting to u32.
>>>
>>> I wonder if we need a BIT32 macro... This is a common issue, it would be
>>> nice to handle it in the macros that define register fields.
>>
>> That's probably a good idea. I think
>>
>> #define BIT32(nr) (1u << (nr))
>>
>> should work correct on all archs. Although I'm not quite sure if nr should be cast to u32, but in my
>> tests a u64 nr doesn't cause type promotion to u64.
> 
> I don't think we need to support nr values larger than 2^32-1 ;-)

That's true, but we might have:

u64 nr = 1;
BIT32(nr)

Afaics, we don't need to cast nr to u32, but maybe that's still the safe thing to do.

>> Anyway, I'd like to merge this fix as it is to get rid of the warning for the merge window.
> 
> Sounds good to me.

Was that a reviewed-by? =)

 Tomi

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