linux-kernel - Re: [PATCH v2 1/3] Bluetooth: btusb: mediatek: use readx_poll

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Date:   Fri, 30 Sep 2022 10:48:22 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     sean.wang@...iatek.com, marcel@...tmann.org,
        johan.hedberg@...il.com, luiz.dentz@...il.com
Cc:     Soul.Huang@...iatek.com, YN.Chen@...iatek.com,
        Leon.Yen@...iatek.com, Eric-SY.Chang@...iatek.com,
        Deren.Wu@...iatek.com, km.lin@...iatek.com,
        robin.chiu@...iatek.com, Eddie.Chen@...iatek.com,
        ch.yeh@...iatek.com, posh.sun@...iatek.com, ted.huang@...iatek.com,
        Stella.Chang@...iatek.com, Tom.Chou@...iatek.com,
        steve.lee@...iatek.com, jsiuda@...gle.com, frankgor@...gle.com,
        abhishekpandit@...gle.com, michaelfsun@...gle.com,
        abhishekpandit@...omium.org, mcchou@...omium.org,
        shawnku@...gle.com, linux-bluetooth@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] Bluetooth: btusb: mediatek: use readx_poll_timeout
 instead of open coding

Il 30/09/22 02:23, sean.wang@...iatek.com ha scritto:
> From: Sean Wang <sean.wang@...iatek.com>
> 
> Use readx_poll_timeout instead of open coding to poll the hardware reset
> status until it is done.
> 
> Signed-off-by: Sean Wang <sean.wang@...iatek.com>
> ---
> The patch is built and tested on the top of the patches
> [v6,1/3] Bluetooth: Add support for hci devcoredump
> [v6,2/3] Bluetooth: btusb: Add btusb devcoredump support
> [v6,3/3] Bluetooth: btintel: Add Intel devcoredump support
> which are contributed from Manish Mandlik
> 
> v2: use 20ms as the unit to poll according to the requirement of
>      readx_poll_timeout
> ---
>   drivers/bluetooth/btusb.c | 32 ++++++++++++++++++--------------
>   1 file changed, 18 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
> index 4eb79e88f1d9..9ef0dc648573 100644
> --- a/drivers/bluetooth/btusb.c
> +++ b/drivers/bluetooth/btusb.c
> @@ -2361,8 +2361,6 @@ static int btusb_send_frame_intel(struct hci_dev *hdev, struct sk_buff *skb)
>   #define MTK_EP_RST_OPT		0x74011890
>   #define MTK_EP_RST_IN_OUT_OPT	0x00010001
>   #define MTK_BT_RST_DONE		0x00000100
> -#define MTK_BT_RESET_WAIT_MS	100
> -#define MTK_BT_RESET_NUM_TRIES	10
>   
>   static void btusb_mtk_wmt_recv(struct urb *urb)
>   {
> @@ -2733,6 +2731,16 @@ static int btusb_mtk_id_get(struct btusb_data *data, u32 reg, u32 *id)
>   	return btusb_mtk_reg_read(data, reg, id);
>   }
>   
> +static u32 btusb_mtk_reset_done(struct hci_dev *hdev)

I'm sorry for not noticing that in v1, but...

...If you call this function "btusb_mtk_reset_done"...

> +{
> +	struct btusb_data *data = hci_get_drvdata(hdev);
> +	u32 val = 0;
> +
> +	btusb_mtk_uhw_reg_read(data, MTK_BT_MISC, &val);
> +
> +	return val;

...you shouldn't return the value of the entire MTK_BT_MISC register,
otherwise you should call this "btusb_mtk_read_bt_misc_reg".

I think that here, you should do

	return val & MTK_BT_RST_DONE;

and then, for the readx_poll_timeout, you simply check if this function
returned 1, like:

	err = readx_poll_timeout(btusb_mtk_reset_done, hdev, val, val,
				 20000, 1000000);

> +}
> +
>   static int btusb_mtk_setup(struct hci_dev *hdev)
>   {
>   	struct btusb_data *data = hci_get_drvdata(hdev);
> @@ -2922,7 +2930,7 @@ static void btusb_mtk_cmd_timeout(struct hci_dev *hdev)
>   {
>   	struct btusb_data *data = hci_get_drvdata(hdev);
>   	u32 val;
> -	int err, retry = 0;
> +	int err;
>   
>   	/* It's MediaTek specific bluetooth reset mechanism via USB */
>   	if (test_and_set_bit(BTUSB_HW_RESET_ACTIVE, &data->flags)) {
> @@ -2953,18 +2961,14 @@ static void btusb_mtk_cmd_timeout(struct hci_dev *hdev)
>   	btusb_mtk_uhw_reg_write(data, MTK_BT_SUBSYS_RST, 0);
>   	btusb_mtk_uhw_reg_read(data, MTK_BT_SUBSYS_RST, &val);
>   
> -	/* Poll the register until reset is completed */
> -	do {
> -		btusb_mtk_uhw_reg_read(data, MTK_BT_MISC, &val);
> -		if (val & MTK_BT_RST_DONE) {
> -			bt_dev_dbg(hdev, "Bluetooth Reset Successfully");
> -			break;
> -		}
> +	err = readx_poll_timeout(btusb_mtk_reset_done, hdev, val,
> +				 val & MTK_BT_RST_DONE,
> +				 20000, 1000000);
> +	if (err < 0)
> +		bt_dev_err(hdev, "Reset timeout");
>   
> -		bt_dev_dbg(hdev, "Polling Bluetooth Reset CR");
> -		retry++;
> -		msleep(MTK_BT_RESET_WAIT_MS);
> -	} while (retry < MTK_BT_RESET_NUM_TRIES);
> +	if (val & MTK_BT_RST_DONE)

You're already checking `if (err < 0)`, so this check is redundant.
If the polling didn't return a timeout, the register value contains
MTK_BT_RST_DONE for sure, so you can safely remove this check.

> +		bt_dev_dbg(hdev, "Bluetooth Reset Successfully");
>   

Regards,
Angelo