From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
To: Raymond Hackley <raymondhackley@protonmail.com>
Cc: broonie@kernel.org, davem@davemloft.net,
devicetree@vger.kernel.org, edumazet@google.com,
jk@codeconstruct.com.au, kuba@kernel.org, lgirdwood@gmail.com,
linux-kernel@vger.kernel.org, michael@walle.cc,
netdev@vger.kernel.org, pabeni@redhat.com, robh+dt@kernel.org,
u.kleine-koenig@pengutronix.de
Subject: Re: [PATCH v2 2/2] NFC: nxp-nci: Add pad supply voltage pvdd-supply
Date: Fri, 9 Jun 2023 21:29:51 +0200 [thread overview]
Message-ID: <7ad5d027-9b15-f59e-aa76-17e498cb7aba@linaro.org> (raw)
In-Reply-To: <20230609173935.84424-1-raymondhackley@protonmail.com>
On 09/06/2023 19:40, Raymond Hackley wrote:
> Hi Krzysztof,
>
> On Friday, June 9th, 2023 at 3:46 PM, Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote:
>
>
>> On 09/06/2023 17:42, Raymond Hackley wrote:
>>
>>> PN547/553, QN310/330 chips on some devices require a pad supply voltage
>>> (PVDD). Otherwise, the NFC won't power up.
>>>
>>> Implement support for pad supply voltage pvdd-supply that is enabled by
>>> the nxp-nci driver so that the regulator gets enabled when needed.
>>>
>>> Signed-off-by: Raymond Hackley raymondhackley@protonmail.com
>>> ---
>>> drivers/nfc/nxp-nci/i2c.c | 42 +++++++++++++++++++++++++++++++++++++++
>>> 1 file changed, 42 insertions(+)
>>>
>>> diff --git a/drivers/nfc/nxp-nci/i2c.c b/drivers/nfc/nxp-nci/i2c.c
>>> index d4c299be7949..1b8877757cee 100644
>>> --- a/drivers/nfc/nxp-nci/i2c.c
>>> +++ b/drivers/nfc/nxp-nci/i2c.c
>>> @@ -35,6 +35,7 @@ struct nxp_nci_i2c_phy {
>>>
>>> struct gpio_desc *gpiod_en;
>>> struct gpio_desc *gpiod_fw;
>>> + struct regulator *pvdd;
>>>
>>> int hard_fault; /*
>>> * < 0 if hardware error occurred (e.g. i2c err)
>>> @@ -263,6 +264,22 @@ static const struct acpi_gpio_mapping acpi_nxp_nci_gpios[] = {
>>> { }
>>> };
>>>
>>> +static void nxp_nci_i2c_poweroff(void *data)
>>> +{
>>> + struct nxp_nci_i2c_phy *phy = data;
>>> + struct device *dev = &phy->i2c_dev->dev;
>>> + struct regulator *pvdd = phy->pvdd;
>>> + int r;
>>> +
>>> + if (!IS_ERR(pvdd) && regulator_is_enabled(pvdd)) {
>>
>>
>> Why do you need these checks? This should be called in correct context,
>> so when regulator is valid and enabled. If you have such checks it
>> suggests that code is buggy and this is being called in wrong contexts.
>>
>
> First condition !IS_ERR(pvdd) is to check if pvdd exists.
> Some devices, msm8916-samsung-serranove for example, doesn't need pvdd or
> have it bound in the device tree:
If regulator is missing you should get a dummy.
But anyway the code will not be executed if you don't get proper regulator.
>
> https://github.com/torvalds/linux/commit/ab0f0987e035f908d670fed7d86efa6fac66c0bb
>
> Without !IS_ERR(pvdd), checking it with regulator_is_enabled(pvdd):
>
> [ 50.161882] 8<--- cut here ---
> [ 50.161906] Unable to handle kernel paging request at virtual address fffffff9 when read
> [ 50.161916] [fffffff9] *pgd=affff841, *pte=00000000, *ppte=00000000
> [ 50.161938] Internal error: Oops: 27 [#1] PREEMPT SMP ARM
>
> Or disabling it directly with regulator_disable(pvdd):
>
> [ 69.439827] 8<--- cut here ---
> [ 69.439841] Unable to handle kernel NULL pointer dereference at virtual address 00000045 when read
> [ 69.439852] [00000045] *pgd=00000000
> [ 69.439864] Internal error: Oops: 5 [#1] PREEMPT SMP ARM
>
> Second condition regulator_is_enabled(pvdd) is to make sure that pvdd is
> disabled with balance.
>
So you have buggy code and to hide the bug you add checks? No, make the
code correct so the check is not needed.
> Similar checks can be found here:
>
> https://elixir.bootlin.com/linux/v6.4-rc5/source/drivers/staging/greybus/arche-apb-ctrl.c#L208
staging driver is not an example...
>
Best regards,
Krzysztof
next prev parent reply other threads:[~2023-06-09 19:30 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-09 15:41 [PATCH v2 0/2] NFC: nxp-nci: Add pad supply voltage pvdd-supply Raymond Hackley
2023-06-09 15:42 ` [PATCH v2 1/2] dt-bindings: nfc: nxp-nci: document pvdd-supply Raymond Hackley
2023-06-09 15:42 ` [PATCH v2 2/2] NFC: nxp-nci: Add pad supply voltage pvdd-supply Raymond Hackley
2023-06-09 15:46 ` Krzysztof Kozlowski
2023-06-09 17:40 ` Raymond Hackley
2023-06-09 19:29 ` Krzysztof Kozlowski [this message]
2023-06-09 19:34 ` Mark Brown
2023-06-09 20:52 ` Raymond Hackley
2023-06-09 20:44 ` Raymond Hackley
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