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Subject: Re: [PATCH v1 3/3] Bluetooth: hci_qca: WAR to handle WCN6750 HW issue
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <1651228073-1999-4-git-send-email-quic_bgodavar@quicinc.com>
Date:   Fri, 29 Apr 2022 16:54:25 +0200
Cc:     Andy Gross <agross@kernel.org>, robh+dt@kernel.org,
        bjorn.andersson@linaro.org, linux-arm-msm@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        Johan Hedberg <johan.hedberg@gmail.com>, mka@chromium.org,
        linux-bluetooth@vger.kernel.org, quic_hemantg@quicinc.com,
        quic_saluvala@quicinc.com, quic_rjliao@quicinc.com,
        mcchou@chromium.org
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References: <1651228073-1999-1-git-send-email-quic_bgodavar@quicinc.com>
 <1651228073-1999-4-git-send-email-quic_bgodavar@quicinc.com>
To:     Balakrishna Godavarthi <quic_bgodavar@quicinc.com>
Precedence: bulk

Hi Balakrishna,

> The patch is workaround for hardware issue on WCN6750.
> On WCN6750 sometimes observed AON power source takes 100ms
> time to fully discharge voltage during OFF. As WCN6750 is
> combo chip for WLAN and BT. If any of the tech area ON is
> triggered during discharge phase, it fails to turn ON.
> To overcome this hardware issue, During BT ON, driver check
> for WLAN_EN pin status. If it high, it will pull BT_EN to high
> immediately else it will wait for 100ms assuming WLAN was just
> powered OFF and then BT_EN will be pulled to high.
> 
> Fixes: d8f97da1b92d2 ("Bluetooth: hci_qca: Add support for QTI Bluetooth chip wcn6750")
> Reviewed-by: Miao-chen Chou <mcchou@chromium.org>
> Signed-off-by: Sai Teja Aluvala <quic_saluvala@quicinc.com>
> Signed-off-by: Balakrishna Godavarthi <quic_bgodavar@quicinc.com>
> ---
> drivers/bluetooth/hci_qca.c | 30 ++++++++++++++++++++++++------
> 1 file changed, 24 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index eab34e2..c3862d1 100644
> --- a/drivers/bluetooth/hci_qca.c
> +++ b/drivers/bluetooth/hci_qca.c
> @@ -219,6 +219,7 @@ struct qca_serdev {
> 	struct hci_uart	 serdev_hu;
> 	struct gpio_desc *bt_en;
> 	struct gpio_desc *sw_ctrl;
> +	struct gpio_desc *wlan_en;
> 	struct clk	 *susclk;
> 	enum qca_btsoc_type btsoc_type;
> 	struct qca_power *bt_power;

I am really against these intermixing of Bluetooth and WiFi details. There is work ongoing to do some sequence power procedure. Maybe that is something you should look into. This is a mess.

And again, we are still hacking around hci_qca.c instead of writing a clean serdev only driver for this hardware. I have the feeling that nobody listens to review comments these days. It is just hacking patches together to get hardware enabled somehow and then disappear.

Regards

Marcel