linux-kernel - Re: [PATCH v3 3/3] i2c: mpc: Use i2c-scl-clk-low-timeout-ms i2c property

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Message-ID: <32777854-fbf6-dad2-ef54-1d1c04086f0b@alliedtelesis.co.nz>
Date:   Tue, 14 Mar 2023 19:47:26 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Andi Shyti <andi.shyti@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC:     "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Wolfram Sang <wsa@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Ryan Chen <ryan_chen@...eedtech.com>
Subject: Re: [PATCH v3 3/3] i2c: mpc: Use i2c-scl-clk-low-timeout-ms i2c
 property

Hi Andi,

On 15/03/23 04:16, Andi Shyti wrote:
> Hi,
>
> On Tue, Mar 14, 2023 at 03:22:52PM +0100, Krzysztof Kozlowski wrote:
>> On 13/03/2023 00:36, Andi Shyti wrote:
>>> "fsl,timeout" is marked as deprecated and replaced by the
>>> "i2c-scl-clk-low-timeout-ms" i2c property.
>>>
>>> Use this latter and, in case it is missing, for back
>>> compatibility, check whether we still have "fsl,timeout" defined.
>>>
>>> Signed-off-by: Andi Shyti <andi.shyti@...nel.org>
>>> Reviewed-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>>> ---
>>>   drivers/i2c/busses/i2c-mpc.c | 12 +++++++++++-
>>>   1 file changed, 11 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
>>> index 87e5c1725750..28f11e30ac50 100644
>>> --- a/drivers/i2c/busses/i2c-mpc.c
>>> +++ b/drivers/i2c/busses/i2c-mpc.c
>>> @@ -843,8 +843,18 @@ static int fsl_i2c_probe(struct platform_device *op)
>>>   			mpc_i2c_setup_8xxx(op->dev.of_node, i2c, clock);
>>>   	}
>>>   
>>> +	/*
>>> +	 * "fsl,timeout" has been marked as deprecated and, to maintain
>>> +	 * backward compatibility, we will only look for it if
>>> +	 * "i2c-scl-clk-low-timeout-ms" is not present.
>>> +	 */
>>>   	result = of_property_read_u32(op->dev.of_node,
>>> -				      "fsl,timeout", &mpc_ops.timeout);
>>> +				      "i2c-scl-clk-low-timeout-ms",
>>> +				      &mpc_ops.timeout);
>>> +	if (result == -EINVAL)
>>> +		result = of_property_read_u32(op->dev.of_node,
>>> +					      "fsl,timeout", &mpc_ops.timeout);
>> Wasn't old property in us and new one is in ms?
> Thanks, Krzysztof! Good catch!
>
> Chris, you are the only user of this property, as of now. Is it
> OK if we keep it ms? I will send a proper patch to do the
> conversion.
>
> To me it doesn't make much sense to have the timeout defined in
> us as that's of the same order of the raising and falling time
> of the clock. Any opinion?
I think it'd be easier to stick to us as then the same code can be used 
to probe both the old property and the new one. However I won't object 
if you adjust for the us to ms conversion between handling the new 
property vs the old one.
>
> Andi