linux-kernel - Re: [PATCH v4 2/2] power: reset: qcom-pon: add support for qcom,pmk8350-pon compatible string

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Message-ID: <e0b13195-0aed-094d-c7af-4581b61d6453@linaro.org>
Date:   Thu, 8 Sep 2022 16:56:48 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Anjelique Melendez <quic_amelende@...cinc.com>, corbet@....net,
        sre@...nel.org, robh+dt@...nel.org, agross@...nel.org,
        bjorn.andersson@...aro.org
Cc:     krzysztof.kozlowski+dt@...aro.org, vkoul@...nel.org,
        linux-doc@...r.kernel.org, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] power: reset: qcom-pon: add support for
 qcom,pmk8350-pon compatible string

On 19/08/2022 22:26, Anjelique Melendez wrote:
> 
> 
> On 7/26/2022 3:27 AM, Krzysztof Kozlowski wrote:
>> On 25/07/2022 21:13, Anjelique Melendez wrote:
>>> Add support for the new "qcom,pmk8350-pon" comptaible string.
>>>
>>> Signed-off-by: Anjelique Melendez <quic_amelende@...cinc.com>
>>> ---
>>>  drivers/power/reset/qcom-pon.c | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/power/reset/qcom-pon.c b/drivers/power/reset/qcom-pon.c
>>> index 4a688741a88a..16bc01738be9 100644
>>> --- a/drivers/power/reset/qcom-pon.c
>>> +++ b/drivers/power/reset/qcom-pon.c
>>> @@ -82,6 +82,7 @@ static const struct of_device_id pm8916_pon_id_table[] = {
>>>  	{ .compatible = "qcom,pm8916-pon", .data = (void *)GEN1_REASON_SHIFT },
>>>  	{ .compatible = "qcom,pms405-pon", .data = (void *)GEN1_REASON_SHIFT },
>>>  	{ .compatible = "qcom,pm8998-pon", .data = (void *)GEN2_REASON_SHIFT },
>>> +	{ .compatible = "qcom,pmk8350-pon", .data = (void *)GEN2_REASON_SHIFT },
>>>  	{ }
>>>  };
>>>  MODULE_DEVICE_TABLE(of, pm8916_pon_id_table);
>>
>> This is now confusing. The new device has entirely different first and
>> second IO address spaces, but you do not code here any differences.
>>
> 
> Based on previous responses to this patch series, it was decided that a new
> "qcom,pmk8350-pon" compatible string is needed to differentiate between gen1/gen2
> vs gen3 children pon devices. Currently the child handles obtaining the register
> address(es) from its parent's regmap in drivers/input/misc/pm8941-pwrkey.c
> (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/input/misc/pm8941-pwrkey.c?h=v6.0-rc1#n287).
> The patch that handled that change can be found at
> https://lore.kernel.org/linux-arm-msm/20220422191239.6271-4-quic_amelende@quicinc.com/.
> 
> This driver, as the parent, does not actually need any changes besides adding the
> new parent compatible string. Specifically this driver handles reboot mode support.
> Everything needed to handle reboot mode is in the first register and reboot mode
> is handled the same as a "qcom,pm8998-pon" parent. The split of the pon register
> in pmk8350 does not affect reboot mode. This is why before we added a new compatible
> string "qcom,pm8998-pon" still worked for gen3 children devices. Even though 2
> registers could be defined in the device tree, as a 2nd register is optional for gen3
> children devices,the fact that this driver uses of_property_read_u32() will ensure that
> the base address used for reboot mode comes from the first register.  
> 

Ah, makes sense.


Best regards,
Krzysztof