Message-Id: <E2DB76D8-414B-4F45-8124-E9AA844E6909@holtmann.org>
Date:   Wed, 14 Mar 2018 21:14:41 +0100
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Thierry Escande <thierry.escande@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Andy Gross <andy.gross@...aro.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        David Brown <david.brown@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Loic Poulain <loic.poulain@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        linux-bluetooth@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/3] Bluetooth: hci_qca: Add serdev support

Hi Thierry,

> Add support for Qualcomm serial slave devices. Probe the serial device,
> retrieve its maximum speed and register a new hci uart device.
> 
> Signed-off-by: Thierry Escande <thierry.escande@...aro.org>
> ---
> 
> v4:
> - Rename divclk4 as susclk (its name in the bt chip)
> - Use gpiod_set_value_cansleep()
> - Replace #include <linux/of.h> with <linux/mod_devicetable.h>
> - Restore dependency on BT_HCIUART
> 
> v3:
> - Remove redundant call to gpiod_set_value() after devm_gpiod_get()
> - Check returned values for clk_set_rate() and clk_prepare_enable()
> - Use clk_disable_unprepare()
> 
> v2:
> - Fix author email
> 
> drivers/bluetooth/Kconfig   |   1 +
> drivers/bluetooth/hci_qca.c | 109 +++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 108 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/bluetooth/Kconfig b/drivers/bluetooth/Kconfig
> index 07e55cd8f8c8..e0f1a6609b68 100644
> --- a/drivers/bluetooth/Kconfig
> +++ b/drivers/bluetooth/Kconfig
> @@ -196,6 +196,7 @@ config BT_HCIUART_BCM
> config BT_HCIUART_QCA
> 	bool "Qualcomm Atheros protocol support"
> 	depends on BT_HCIUART
> +	depends on BT_HCIUART_SERDEV
> 	select BT_HCIUART_H4
> 	select BT_QCA
> 	help
> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> index 05ec530b8a3a..6cf0d1d4595a 100644
> --- a/drivers/bluetooth/hci_qca.c
> +++ b/drivers/bluetooth/hci_qca.c
> @@ -29,7 +29,11 @@
>  */
> 
> #include <linux/kernel.h>
> +#include <linux/clk.h>
> #include <linux/debugfs.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/serdev.h>
> 
> #include <net/bluetooth/bluetooth.h>
> #include <net/bluetooth/hci_core.h>
> @@ -50,6 +54,9 @@
> #define IBS_TX_IDLE_TIMEOUT_MS		2000
> #define BAUDRATE_SETTLE_TIMEOUT_MS	300
> 
> +/* susclk rate */
> +#define SUSCLK_RATE_32KHZ	32768
> +
> /* HCI_IBS transmit side sleep protocol states */
> enum tx_ibs_states {
> 	HCI_IBS_TX_ASLEEP,
> @@ -111,6 +118,12 @@ struct qca_data {
> 	u64 votes_off;
> };
> 
> +struct qca_serdev {
> +	struct hci_uart	 serdev_hu;
> +	struct gpio_desc *bt_en;
> +	struct clk	 *susclk;
> +};
> +
> static void __serial_clock_on(struct tty_struct *tty)
> {
> 	/* TODO: Some chipset requires to enable UART clock on client
> @@ -386,6 +399,7 @@ static void hci_ibs_wake_retrans_timeout(struct timer_list *t)
> /* Initialize protocol */
> static int qca_open(struct hci_uart *hu)
> {
> +	struct qca_serdev *qcadev;
> 	struct qca_data *qca;
> 
> 	BT_DBG("hu %p qca_open", hu);
> @@ -444,6 +458,13 @@ static int qca_open(struct hci_uart *hu)
> 	timer_setup(&qca->tx_idle_timer, hci_ibs_tx_idle_timeout, 0);
> 	qca->tx_idle_delay = IBS_TX_IDLE_TIMEOUT_MS;
> 
> +	if (hu->serdev) {
> +		serdev_device_open(hu->serdev);
> +
> +		qcadev = serdev_device_get_drvdata(hu->serdev);
> +		gpiod_set_value_cansleep(qcadev->bt_en, 1);
> +	}
> +
> 	BT_DBG("HCI_UART_QCA open, tx_idle_delay=%u, wake_retrans=%u",
> 	       qca->tx_idle_delay, qca->wake_retrans);
> 
> @@ -512,6 +533,7 @@ static int qca_flush(struct hci_uart *hu)
> /* Close protocol */
> static int qca_close(struct hci_uart *hu)
> {
> +	struct qca_serdev *qcadev;
> 	struct qca_data *qca = hu->priv;
> 
> 	BT_DBG("hu %p qca close", hu);
> @@ -525,6 +547,13 @@ static int qca_close(struct hci_uart *hu)
> 	destroy_workqueue(qca->workqueue);
> 	qca->hu = NULL;
> 
> +	if (hu->serdev) {
> +		serdev_device_close(hu->serdev);
> +
> +		qcadev = serdev_device_get_drvdata(hu->serdev);
> +		gpiod_set_value_cansleep(qcadev->bt_en, 0);
> +	}
> +
> 	kfree_skb(qca->rx_skb);
> 
> 	hu->priv = NULL;
> @@ -885,6 +914,14 @@ static int qca_set_baudrate(struct hci_dev *hdev, uint8_t baudrate)
> 	return 0;
> }
> 
> +static inline void host_set_baudrate(struct hci_uart *hu, unsigned int speed)
> +{
> +	if (hu->serdev)
> +		serdev_device_set_baudrate(hu->serdev, speed);
> +	else
> +		hci_uart_set_baudrate(hu, speed);
> +}
> +
> static int qca_setup(struct hci_uart *hu)
> {
> 	struct hci_dev *hdev = hu->hdev;
> @@ -905,7 +942,7 @@ static int qca_setup(struct hci_uart *hu)
> 		speed = hu->proto->init_speed;
> 
> 	if (speed)
> -		hci_uart_set_baudrate(hu, speed);
> +		host_set_baudrate(hu, speed);
> 
> 	/* Setup user speed if needed */
> 	speed = 0;
> @@ -924,7 +961,7 @@ static int qca_setup(struct hci_uart *hu)
> 				   ret);
> 			return ret;
> 		}
> -		hci_uart_set_baudrate(hu, speed);
> +		host_set_baudrate(hu, speed);
> 	}
> 
> 	/* Setup patch / NVM configurations */
> @@ -958,12 +995,80 @@ static struct hci_uart_proto qca_proto = {
> 	.dequeue	= qca_dequeue,
> };
> 
> +static int qca_serdev_probe(struct serdev_device *serdev)
> +{
> +	struct qca_serdev *qcadev;
> +	int err;
> +
> +	qcadev = devm_kzalloc(&serdev->dev, sizeof(*qcadev), GFP_KERNEL);
> +	if (!qcadev)
> +		return -ENOMEM;
> +
> +	qcadev->serdev_hu.serdev = serdev;
> +	serdev_device_set_drvdata(serdev, qcadev);
> +
> +	qcadev->bt_en = devm_gpiod_get(&serdev->dev, "bt-disable-n",
> +				       GPIOD_OUT_LOW);
> +	if (IS_ERR(qcadev->bt_en)) {
> +		dev_err(&serdev->dev, "failed to acquire bt-disable-n gpio\n");
> +		return PTR_ERR(qcadev->bt_en);
> +	}
> +
> +	qcadev->susclk = devm_clk_get(&serdev->dev, NULL);
> +	if (IS_ERR(qcadev->susclk)) {
> +		dev_err(&serdev->dev, "failed to acquire clk\n");
> +		return PTR_ERR(qcadev->susclk);
> +	}
> +
> +	err = clk_set_rate(qcadev->susclk, SUSCLK_RATE_32KHZ);
> +	if (err)
> +		return err;
> +
> +	err = clk_prepare_enable(qcadev->susclk);
> +	if (err)
> +		return err;
> +
> +	err = hci_uart_register_device(&qcadev->serdev_hu, &qca_proto);
> +	if (err)
> +		clk_disable_unprepare(qcadev->susclk);
> +
> +	return err;
> +}
> +
> +static void qca_serdev_remove(struct serdev_device *serdev)
> +{
> +	struct qca_serdev *qcadev = serdev_device_get_drvdata(serdev);
> +
> +	hci_uart_unregister_device(&qcadev->serdev_hu);
> +
> +	clk_disable_unprepare(qcadev->susclk);
> +}
> +
> +static const struct of_device_id qca_bluetooth_of_match[] = {
> +	{ .compatible = "qcom,qca6174-bt" },
> +	{ /* sentinel */ }
> +};

so I am fine taking this patch after we agree on the GPIO naming in the DT file, however ..

While looking into the 3-Wire serdev patches to support Realtek devices, I realized that hacking serdev support into hci_uart.ko is actually pretty much a huge mess. It works, but it is also not pretty and makes the code really complicated and spaghetti like.

The nice thing about hci_uart.ko is that all vendor specific stuff is in a separate file (in comparison to btusb.ko), but the not so nice part is that it is largely messy and complicated.

So I have a basic btuart.ko driver ready that speaks only H:4 and serdev. It is clean and tiny and I added already basic Broadcom support to it. So maybe going the path like btusb.ko to select different setup routines is good enough. I need to work out a few kinks in it, but it is a lot cleaner from a code perspective. In addition, I have the basics for a bt3wire.ko driver that will then take H:5 instead of H:4.

I will send them around shortly and maybe it makes sense to go down this path and integrate QCA support there. I currently only have RPi3 on my desk with serdev attached Broadcom chip. So it would needs others testing if this can work.

Regards

Marcel

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