i2c/synquacer: Deal with optional PCLK correctly

From: Ard Biesheuvel <ardb@kernel.org>

ACPI boot does not provide clocks and regulators, but instead, provides
the PCLK rate directly, and enables the clock in firmware. So deal
gracefully with this.

Fixes: 55750148e559 ("i2c: synquacer: Fix an error handling path in synquacer_i2c_probe()")
Cc: <stable@vger.kernel.org>
Cc: Andi Shyti <andi.shyti@kernel.org>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
https://lore.kernel.org/all/CAMj1kXFH+zB_YuUS+vaEpguhuVGLYbQw55VNDCxnBfSPe6b-nw@mail.gmail.com/T/#u

 drivers/i2c/busses/i2c-synquacer.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

(trying to merge t and cc fields from Ard's and Andy's messages)


Le 12/09/2024 à 12:46, Ard Biesheuvel a écrit :
> From: Ard Biesheuvel <ardb@kernel.org>
>
> ACPI boot does not provide clocks and regulators, but instead, provides
> the PCLK rate directly, and enables the clock in firmware. So deal
> gracefully with this.
>
> Fixes: 55750148e559 ("i2c: synquacer: Fix an error handling path in synquacer_i2c_probe()")

Hi,

If that matters, I'm not sure that the Fixes tag is correct.

IIUC, either it is a new functionally that is added (now it works with 
ACPI...), or if considered as a fix, then I think that it is linked to 
commit 0d676a6c4390 ("i2c: add support for Socionext SynQuacer I2C 
controller").

I don't think that 55750148e559 introduced a regression. The issue seems 
to be there since the beginning. Agreed?

If yes, then it may be needed to backport it in older kernels too.

CJ

> Cc: <stable@vger.kernel.org>
> Cc: Andi Shyti <andi.shyti@kernel.org>
> Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> https://lore.kernel.org/all/CAMj1kXFH+zB_YuUS+vaEpguhuVGLYbQw55VNDCxnBfSPe6b-nw@mail.gmail.com/T/#u
>
>   drivers/i2c/busses/i2c-synquacer.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-synquacer.c b/drivers/i2c/busses/i2c-synquacer.c
> index 4eccbcd0fbfc..bbb9062669e4 100644
> --- a/drivers/i2c/busses/i2c-synquacer.c
> +++ b/drivers/i2c/busses/i2c-synquacer.c
> @@ -550,12 +550,13 @@ static int synquacer_i2c_probe(struct platform_device *pdev)
>   	device_property_read_u32(&pdev->dev, "socionext,pclk-rate",
>   				 &i2c->pclkrate);
>   
> -	pclk = devm_clk_get_enabled(&pdev->dev, "pclk");
> +	pclk = devm_clk_get_optional_enabled(&pdev->dev, "pclk");
>   	if (IS_ERR(pclk))
>   		return dev_err_probe(&pdev->dev, PTR_ERR(pclk),
>   				     "failed to get and enable clock\n");
>   
> -	i2c->pclkrate = clk_get_rate(pclk);
> +	if (pclk)
> +		i2c->pclkrate = clk_get_rate(pclk);
>   
>   	if (i2c->pclkrate < SYNQUACER_I2C_MIN_CLK_RATE ||
>   	    i2c->pclkrate > SYNQUACER_I2C_MAX_CLK_RATE)

Le 12/09/2024 à 19:12, Ard Biesheuvel a écrit :
> On Thu, 12 Sept 2024 at 19:11, Marion & Christophe JAILLET
> <christophe.jaillet@wanadoo.fr> wrote:
>>
>> (trying to merge t and cc fields from Ard's and Andy's messages)
>>
>>
>> Le 12/09/2024 à 12:46, Ard Biesheuvel a écrit :
>>> From: Ard Biesheuvel <ardb@kernel.org>
>>>
>>> ACPI boot does not provide clocks and regulators, but instead, provides
>>> the PCLK rate directly, and enables the clock in firmware. So deal
>>> gracefully with this.
>>>
>>> Fixes: 55750148e559 ("i2c: synquacer: Fix an error handling path in synquacer_i2c_probe()")
>>
>> Hi,
>>
>> If that matters, I'm not sure that the Fixes tag is correct.
>>
>> IIUC, either it is a new functionally that is added (now it works with
>> ACPI...), or if considered as a fix, then I think that it is linked to
>> commit 0d676a6c4390 ("i2c: add support for Socionext SynQuacer I2C
>> controller").
>>
>> I don't think that 55750148e559 introduced a regression. The issue seems
>> to be there since the beginning. Agreed?
>>
> 
> No.
> 
> The original code used IS_ERR_OR_NULL() to explicitly permit the case
> where no clock exists at all.

Got it, this is not related to the removed _OR_NULL, but to the change 
of logic I've introduce.

	if (!IS_ERR)
		do_something_and_continue;
	if_NOENT_was_returned_we_still_get_there();

which became:
	if (IS_ERR)
		return;
	we_can_get_there_with_NOENT_anymore();

My bad!

CJ

> 
> This has worked fine with ACPI boot for many years before this fix was applied.
> 
>> If yes, then it may be needed to backport it in older kernels too.
>>
> 
> No, it used to work. The fix is what broke ACPI boot.
>

Hi Ard,

On Thu, Sep 12, 2024 at 12:46:31PM GMT, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@kernel.org>
> 
> ACPI boot does not provide clocks and regulators, but instead, provides
> the PCLK rate directly, and enables the clock in firmware. So deal
> gracefully with this.
> 
> Fixes: 55750148e559 ("i2c: synquacer: Fix an error handling path in synquacer_i2c_probe()")
> Cc: <stable@vger.kernel.org>
> Cc: Andi Shyti <andi.shyti@kernel.org>
> Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

I'm sorry for the delay, but I needed to wait for the previous
batch of fixes to be merged.

Merged to i2c/i2c-host-next.

Thanks,
Andi

On Fri, 20 Sept 2024 at 11:03, Andi Shyti <andi.shyti@kernel.org> wrote:
>
> Hi Ard,
>
> On Thu, Sep 12, 2024 at 12:46:31PM GMT, Ard Biesheuvel wrote:
> > From: Ard Biesheuvel <ardb@kernel.org>
> >
> > ACPI boot does not provide clocks and regulators, but instead, provides
> > the PCLK rate directly, and enables the clock in firmware. So deal
> > gracefully with this.
> >
> > Fixes: 55750148e559 ("i2c: synquacer: Fix an error handling path in synquacer_i2c_probe()")
> > Cc: <stable@vger.kernel.org>
> > Cc: Andi Shyti <andi.shyti@kernel.org>
> > Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>
> I'm sorry for the delay, but I needed to wait for the previous
> batch of fixes to be merged.
>
> Merged to i2c/i2c-host-next.
>

Thanks. No need to treat it with urgency on my behalf.