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Message-ID: <c0f7036d-c129-400b-85a2-1414ec3d2622@quicinc.com>
Date: Mon, 22 Apr 2024 08:14:33 +0800
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Subject: Re: [PATCH v4 0/2] Fix two regression issues for QCA controllers
To: Krzysztof Kozlowski <krzk@kernel.org>, Wren Turkal <wt@penguintechs.org>,
        <luiz.dentz@gmail.com>, <luiz.von.dentz@intel.com>,
        <marcel@holtmann.org>
CC: <linux-bluetooth@vger.kernel.org>, <bartosz.golaszewski@linaro.org>,
        <regressions@lists.linux.dev>
References: <1713564212-21725-1-git-send-email-quic_zijuhu@quicinc.com>
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 <369512e2-f091-4370-bce5-9ac32178dc4d@penguintechs.org>
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From: quic_zijuhu <quic_zijuhu@quicinc.com>
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On 4/22/2024 2:41 AM, Krzysztof Kozlowski wrote:
> On 21/04/2024 09:44, Wren Turkal wrote:
>> On 4/20/24 3:06 PM, Zijun Hu wrote:
>>> This patch series are to fix below 2 regression issues for QCA controllers
>>> 1) BT can't be enabled once BT was ever enabled for QCA_QCA6390
>>> 2) BT can't be enabled after disable then warm reboot for QCA_QCA6390
>>
>> @Zijun @Krzysztof and @Bartosz Would it be helpful for me to test these 
>> to ensure they fix the issues I reported?
>>
> 
> I look forward to someone testing these on other hardware, not yours. On
> the hardware where the original issues were happening leading to this
> changes, e.g. RB5.
> 
> Anyway, the problem here is poor explanation of the problem which did
> not improve in v3 and v4. Instead I receive explanations like:
> 
> "this is shutdown of serdev and not hdev's shutdown."
> Not related...
> 
this is the reply for secondary issue. i believe i have given much
explain for my fix for the 2nd issue as shown by below links.
let me add a bit more explanation within the ending "For the 2nd issue"
section, supposed you known much for generic flag
HCI_QUIRK_NON_PERSISTENT_SETUP, otherwise, see header comment for the
quirk. also supposed you see commit history to find why
qca_serdev_shutdown() was introduced for QCA6390.
https://lore.kernel.org/all/fe1a0e3b-3408-4a33-90e9-d4ffcfc7a99b@quicinc.com/
> "now. you understood why your merged change as shown link of 4) have
> problems and introduced our discussed issue, right?"
> 
this is the reply for the first issue as shown by below link. it almost
have the same description as the following "For 1st issue:" section.
i believe it have clear illustration why the commit have bugs.
https://lore.kernel.org/all/2166fc66-9340-4e8c-8662-17a19a7d8ce6@linaro.org/
> No. I did not understand and I feel I am wasting here time.
> > Code could be correct, could be wrong. Especially second patch looks
> suspicious. But the way Zijun Hu explains it and the way Zijun Hu
> responds is not helping at all.
> 
> Sorry, with such replies to review, it is not worth my time.
> 
> Best regards,
> Krzysztof
> 
Hi luiz,marcel

it is time for me to request you give comments for our discussion
and for my fixes, Let me explain the 1st issue then 2nd one.

For 1st issue:
1) the following commit will cause serious regression issue for QCA
controllers, and it has been merged with linus's mainline kernel.

Commit 56d074d26c58 ("Bluetooth: hci_qca: don't use IS_ERR_OR_NULL()
with gpiod_get_optional()").

2) the regression issue is described by [PATCH v4 1/2] commit message
  as following:
  BT can't be enabled after below steps:
  cold boot -> enable BT -> disable BT -> warm reboot -> BT enable
failure if property enable-gpios is not configured within DT|ACPI for
QCA_QCA6390.
  i will verify and confirm if QCA_QCA2066 and QCA_ROME also are impacted.

3) let me explain the bug point for commit mentioned by 1), its
   commit message and bug change applet are shown below.

The optional variants for the gpiod_get() family of functions return
NULL if the GPIO in question is not associated with this device. They
return ERR_PTR() on any other error. NULL descriptors are graciously
handled by GPIOLIB and can be safely passed to any of the GPIO consumer
interfaces as they will return 0 and act as if the function succeeded.
If one is using the optional variant, then there's no point in checking
for NULL.

 		qcadev->bt_en = devm_gpiod_get_optional(&serdev->dev, "enable",
 					       GPIOD_OUT_LOW);
-		if (IS_ERR_OR_NULL(qcadev->bt_en)) {
+		if (IS_ERR(qcadev->bt_en)) {
 			dev_warn(&serdev->dev, "failed to acquire enable gpio\n");
 			power_ctrl_enabled = false;
 		}
   3.1) we only need to discuss how to handle case "qcadev->bt_en ==
NULL" since this is only difference between the commit and BT original
design.
   3.2) BT original design are agree with the point of above commit
message that case "qcadev->bt_en == NULL" should not be treated as
error, so BT original design does not do error return for the case and
use dev_warn() instead of dev_err() to give.
   3.3) the commit misunderstands BT original design and wrongly think
BT original design take "qcadev->bt_en == NULL" as error case,
so change the following flag power_ctrl_enabled set logic and cause
discussed issue.

For the 2nd issue:
1) the following commit will cause below regression issue for QCA_QCA6390.
Commit 272970be3dab ("Bluetooth: hci_qca: Fix driver shutdown on closed
    serdev")

2) the regression issue is described by [PATCH v4 2/2] commit message
  as following:
  BT can't be enabled after below steps:
  cold boot -> enable BT -> disable BT -> warm reboot -> BT enable
failure if property enable-gpios is not configured within DT|ACPI for
QCA_QCA6390.

3) qca_serdev_shutdown() is serdev's shutdown and not hdev's shutdown()
it should not and also never get chance to be invoked even if BT is
disabled at above 2) step.  qca_serdev_shutdown() need to send the VSC
to reset controller during warm reset phase of above 2) steps.