linux-hardening - Re: [PATCH 11/11] power: supply: qcom

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Message-ID: <53a2cdba-0fb8-4b99-b58e-9318b1bd8ef6@oss.qualcomm.com>
Date: Mon, 23 Jun 2025 18:40:07 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Casey Connolly <casey.connolly@...aro.org>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Sebastian Reichel <sre@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Kees Cook <kees@...nel.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sebastian Reichel <sebastian.reichel@...labora.com>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH 11/11] power: supply: qcom_smbx: program aicl rerun time

On 6/23/25 6:33 PM, Casey Connolly wrote:
> 
> 
> On 6/20/25 19:00, Konrad Dybcio wrote:
>> On 6/19/25 4:55 PM, Casey Connolly wrote:
>>> We don't know what the bootloader programmed here, but we want to have a
>>> consistent value. Program the automatic input current limit detection to
>>> re-run every 3 seconds. This seems to be necessary at least for smb5.
>>>
>>> Signed-off-by: Casey Connolly <casey.connolly@...aro.org>
>>> ---
>>>   drivers/power/supply/qcom_smbx.c | 6 ++++++
>>>   1 file changed, 6 insertions(+)
>>>
>>> diff --git a/drivers/power/supply/qcom_smbx.c b/drivers/power/supply/qcom_smbx.c
>>> index d902f3f43548191d3d0310ce90e699918ed0f16f..b723dba5b86daefb238ee6aae19b1b7e5236fce3 100644
>>> --- a/drivers/power/supply/qcom_smbx.c
>>> +++ b/drivers/power/supply/qcom_smbx.c
>>> @@ -1091,8 +1091,14 @@ static int smb_probe(struct platform_device *pdev)
>>>       if (rc < 0)
>>>           return dev_err_probe(chip->dev, rc,
>>>                        "Couldn't write fast charge current cfg");
>>>   +    rc = regmap_write_bits(chip->regmap, chip->base + AICL_RERUN_TIME_CFG,
>>> +                   AICL_RERUN_TIME_MASK, AIC_RERUN_TIME_3_SECS);
>>
>> FWIW a random downstream clone I have sets 0x01 which is claimed to
>> mean "every 12s" instead
> 
> hmm I saw that too, I think more documentation would be needed to understand this properly (I'm not exactly clear on what this actually means, when the AICL would re-run, etc).
> 
> I have reports that this works ok, so I'd just leave it unless we have info to suggest otherwise.

Well, in case of such lack of understanding I'd much prefer to see
a magic number that shipped on hundreds of millions of devices than
a magic number that was confirmed working on a couple dozen.. especially
since this looks like an improvement that people who had their hand in
the hw design wouldn't generally overlook unless there was reasons
(e.g. compatibility or some sort of a quirk)

Konrad