netdev - Re: [PATCH 02/10] rtw88: Drop rf

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Message-ID: <af80039404cb3eb9dd036ab5734ddea95d31cf49.camel@realtek.com>
Date:   Fri, 20 May 2022 03:49:06 +0000
From:   Pkshih <pkshih@...ltek.com>
To:     "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>
CC:     "johannes@...solutions.net" <johannes@...solutions.net>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "neojou@...il.com" <neojou@...il.com>,
        "kvalo@...nel.org" <kvalo@...nel.org>,
        "tony0620emma@...il.com" <tony0620emma@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "martin.blumenstingl@...glemail.com" 
        <martin.blumenstingl@...glemail.com>,
        "linux@...i-kroll.de" <linux@...i-kroll.de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH 02/10] rtw88: Drop rf_lock

On Wed, 2022-05-18 at 10:23 +0200, Sascha Hauer wrote:
> The rtwdev->rf_lock spinlock protects the rf register accesses in
> rtw_read_rf() and rtw_write_rf(). Most callers of these functions hold
> rtwdev->mutex already with the exception of the callsites in the debugfs
> code. The debugfs code doesn't justify an extra lock, so acquire the mutex
> there as well before calling rf register accessors and drop the now
> unnecessary spinlock.
> 
> Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
> ---
>  drivers/net/wireless/realtek/rtw88/debug.c | 11 +++++++++++
>  drivers/net/wireless/realtek/rtw88/hci.h   |  9 +++------
>  drivers/net/wireless/realtek/rtw88/main.c  |  1 -
>  drivers/net/wireless/realtek/rtw88/main.h  |  3 ---
>  4 files changed, 14 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtw88/debug.c
> b/drivers/net/wireless/realtek/rtw88/debug.c
> index 1a52ff585fbc7..ba5ba852efb8c 100644
> --- a/drivers/net/wireless/realtek/rtw88/debug.c
> +++ b/drivers/net/wireless/realtek/rtw88/debug.c
> 

[...]

> @@ -523,6 +527,8 @@ static int rtw_debug_get_rf_dump(struct seq_file *m, void *v)
>  	u32 addr, offset, data;
>  	u8 path;
>  
> +	mutex_lock(&rtwdev->mutex);
> +
>  	for (path = 0; path < rtwdev->hal.rf_path_num; path++) {
>  		seq_printf(m, "RF path:%d\n", path);
>  		for (addr = 0; addr < 0x100; addr += 4) {
> @@ -537,6 +543,8 @@ static int rtw_debug_get_rf_dump(struct seq_file *m, void *v)
>  		seq_puts(m, "\n");
>  	}
>  
> +	mutex_unlock(&rtwdev->mutex);
> +
>  	return 0;
>  }
> 

This will take time to dump all RF registers for debugging
purpose. For PCI interface, I think this would be okay.
Could you try to dump registers via debufs while you are
using a USB WiFi device, such as play Youtube or download files...

If it doesn't work very well, I suggest to use rf_mutex to
replace rf_lock inplace, but not just remove rf_lock.

--
Ping-Ke