Re: [PATCHv2] Bluetooth: quirk disabling LE Read Transmit Power

[Aditya Garg <gargaditya08@live.com>]

> On 25-Nov-2021, at 5:56 PM, Thorsten Leemhuis <regressions@leemhuis.info> wrote:
> 
> Hi, this is your Linux kernel regression tracker speaking again.
> 
> On 19.11.21 17:59, Aditya Garg wrote:
>>> On 18-Nov-2021, at 12:31 AM, Marcel Holtmann <marcel@holtmann.org> wrote:
>>>>> So if this just affects two macs, why can't the fix be realized as a
>>>>> quirk that is only enabled on those two systems? Or are they impossible
>>>>> to detect clearly via DMI data or something like that?
>>>> 
>>>> I think we should be able to quirk based off the acpi _CID "apple-uart-blth"
>>>> or _HID "BCM2E7C". Marcel suggested quirking based of the acpi table here
>>>> https://lore.kernel.org/linux-bluetooth/1D2217A9-EA73-4D93-8D0B-5BC2718D4788@holtmann.org/
>>>> 
>>>> This would catch some unaffected Macs, but they don't support the LE Read
>>>> Transmit Power command anyway (the affected macs were released after it
>>>> was added to the Bluetooth spec, while the unaffected Macs were released
>>>> before it was added to the spec, and thus don't support it).
>>>> 
>>>> I'm not sure how to go about applying a quirk based off this, there are
>>>> quirks in drivers/bluetooth/hci_bcm.c (no_early_set_baudrate and
>>>> drive_rts_on_open), but they don't seem to be based off acpi ids.
>>>> 
>>>> It might be simpler to make it ignore the Unknown Command error, like
>>>> in this patch https://lore.kernel.org/linux-bluetooth/CABBYNZLjSfcG_KqTEbL6NOSvHhA5-b1t_S=3FQP4=GwW21kuzg@mail.gmail.com/
>>>> however that only applies on bluetooth-next and needed the status it
>>>> checks for to be -56, not 0x01.
>>> 
>>> so we abstain from try-and-error sending of commands. The Bluetooth spec
>>> has a list of supported commands that a host can query for a reason. This
>>> is really broken behavior of the controller and needs to be pointed out as
>>> such.
>> Well all I can do is provide you any logs or information I can. But we do really wish to get this regression fixed soon.
>>> 
>>> The question is just how we quirk it.
> 
> This thread once again looks stalled and smells a lot like "everyone
> agrees that his should be fixed, but afaics nobody submitted a fix or
> committed to work on one". Please speak up if my impression is wrong, as
> this is a regression and thus needs to be fixed, ideally quickly. Part
> of my job is to make that happen and thus remind developers and
> maintainers about this until we have a fix.
On the basis of DMI data, I have made this patch to disable read transmit power on 16,1. I have tested this on my 16,1 successfully. Still consider this as a draft as more models have to be added. I am sending this to get the approval of the maintainers whether this quirk is acceptable or not. If yes, I shall send the final patch.

From 3dab2e1e9e0b266574f5f010efc6680417fb0c61 Mon Sep 17 00:00:00 2001
From: Aditya Garg <gargaditya08@live.com>
Date: Fri, 26 Nov 2021 18:28:46 +0530
Subject: [PATCH] Add quirk to disable read transmit power on MacBook Pro 16
 inch, 2019

---
 net/bluetooth/hci_core.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 8d33aa64846b1c..d11064cb3666ef 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -32,6 +32,7 @@
 #include <linux/property.h>
 #include <linux/suspend.h>
 #include <linux/wait.h>
+#include <linux/dmi.h>
 #include <asm/unaligned.h>
 
 #include <net/bluetooth/bluetooth.h>
@@ -461,9 +462,23 @@ static void hci_set_event_mask_page_2(struct hci_request *req)
 			    sizeof(events), events);
 }
 
+static const struct dmi_system_id fix_up_apple_bluetooth[] = {
+	{
+		/* Match for Apple MacBook Pro 16 inch, 2019 which needs
+		 * read transmit power to be disabled
+		 */
+		.matches = {
+			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro16,1"),
+		},
+	},
+	{ }
+};
+
 static int hci_init3_req(struct hci_request *req, unsigned long opt)
 {
 	struct hci_dev *hdev = req->hdev;
+	const struct dmi_system_id *dmi_id;
 	u8 p;
 
 	hci_setup_event_mask(req);
@@ -619,7 +634,8 @@ static int hci_init3_req(struct hci_request *req, unsigned long opt)
 			hci_req_add(req, HCI_OP_LE_READ_ADV_TX_POWER, 0, NULL);
 		}
 
-		if (hdev->commands[38] & 0x80) {
+		dmi_id = dmi_first_match(fix_up_apple_bluetooth);
+		if (hdev->commands[38] & 0x80 && (!dmi_id)) {
 			/* Read LE Min/Max Tx Power*/
 			hci_req_add(req, HCI_OP_LE_READ_TRANSMIT_POWER,
 				    0, NULL);
> 
> Ciao, Thorsten
> 
> #regzbot title bluetooth: "Query LE tx power on startup" broke Bluetooth
> on MacBookPro16,1
> #regzbot poke