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From: Matt Redfearn <matt.redfearn@mips.com>
To: Michal Simek <michal.simek@xilinx.com>,
	<linux-kernel@vger.kernel.org>, <monstr@monstr.eu>
Cc: stable <stable@vger.kernel.org>, Jiri Slaby <jslaby@suse.com>,
	Douglas Anderson <dianders@chromium.org>,
	<linux-serial@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jeffy Chen <jeffy.chen@rock-chips.com>
Subject: Re: [PATCH] serial: 8250_early: Setup divider when uartclk is passed
Date: Mon, 23 Apr 2018 14:21:53 +0100	[thread overview]
Message-ID: <f8c69fee-8889-f0aa-1235-b7a65068238b@mips.com> (raw)
In-Reply-To: <93a7871c8654a6273b1ab35a8071e9f830e2a0c8.1524475087.git.michal.simek@xilinx.com>

Hi Michal

On 23/04/18 10:18, Michal Simek wrote:
> device->baud is always non zero value because it is checked already in
> early_serial8250_setup() before init_port is called.

True, currently init_port is only called from the one location and so 
the test is a little redundant, though I don't see the harm in testing 
both inputs to the divisor calculation immediately before use such that 
any future call path avoids setting a bad divisor.

> 
> Fixes: 0ff3ab701963 ("serial: 8250_early: Only set divisor if valid clk & baud")
> Cc: stable <stable@vger.kernel.org>

Even if the test is dropped going forward, I wouldn't consider it's 
presence a "bug" such that a fix needs to be backported.

Thanks,
Matt

> Signed-off-by: Michal Simek <michal.simek@xilinx.com>
> ---
> 
>   drivers/tty/serial/8250/8250_early.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
> index ae6a256524d8..5cd8c36c8fcc 100644
> --- a/drivers/tty/serial/8250/8250_early.c
> +++ b/drivers/tty/serial/8250/8250_early.c
> @@ -122,7 +122,7 @@ static void __init init_port(struct earlycon_device *device)
>   	serial8250_early_out(port, UART_FCR, 0);	/* no fifo */
>   	serial8250_early_out(port, UART_MCR, 0x3);	/* DTR + RTS */
>   
> -	if (port->uartclk && device->baud) {
> +	if (port->uartclk) {
>   		divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
>   		c = serial8250_early_in(port, UART_LCR);
>   		serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
> 

WARNING: multiple messages have this Message-ID (diff)
From: Matt Redfearn <matt.redfearn@mips.com>
To: Michal Simek <michal.simek@xilinx.com>,
	linux-kernel@vger.kernel.org, monstr@monstr.eu
Cc: stable <stable@vger.kernel.org>, Jiri Slaby <jslaby@suse.com>,
	Douglas Anderson <dianders@chromium.org>,
	linux-serial@vger.kernel.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jeffy Chen <jeffy.chen@rock-chips.com>
Subject: Re: [PATCH] serial: 8250_early: Setup divider when uartclk is passed
Date: Mon, 23 Apr 2018 14:21:53 +0100	[thread overview]
Message-ID: <f8c69fee-8889-f0aa-1235-b7a65068238b@mips.com> (raw)
In-Reply-To: <93a7871c8654a6273b1ab35a8071e9f830e2a0c8.1524475087.git.michal.simek@xilinx.com>

Hi Michal

On 23/04/18 10:18, Michal Simek wrote:
> device->baud is always non zero value because it is checked already in
> early_serial8250_setup() before init_port is called.

True, currently init_port is only called from the one location and so 
the test is a little redundant, though I don't see the harm in testing 
both inputs to the divisor calculation immediately before use such that 
any future call path avoids setting a bad divisor.

> 
> Fixes: 0ff3ab701963 ("serial: 8250_early: Only set divisor if valid clk & baud")
> Cc: stable <stable@vger.kernel.org>

Even if the test is dropped going forward, I wouldn't consider it's 
presence a "bug" such that a fix needs to be backported.

Thanks,
Matt

> Signed-off-by: Michal Simek <michal.simek@xilinx.com>
> ---
> 
>   drivers/tty/serial/8250/8250_early.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
> index ae6a256524d8..5cd8c36c8fcc 100644
> --- a/drivers/tty/serial/8250/8250_early.c
> +++ b/drivers/tty/serial/8250/8250_early.c
> @@ -122,7 +122,7 @@ static void __init init_port(struct earlycon_device *device)
>   	serial8250_early_out(port, UART_FCR, 0);	/* no fifo */
>   	serial8250_early_out(port, UART_MCR, 0x3);	/* DTR + RTS */
>   
> -	if (port->uartclk && device->baud) {
> +	if (port->uartclk) {
>   		divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
>   		c = serial8250_early_in(port, UART_LCR);
>   		serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
> 

  reply	other threads:[~2018-04-23 13:21 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-23  9:18 [PATCH] serial: 8250_early: Setup divider when uartclk is passed Michal Simek
2018-04-23  9:18 ` Michal Simek
2018-04-23 13:21 ` Matt Redfearn [this message]
2018-04-23 13:21   ` Matt Redfearn
2018-04-24 12:27   ` Michal Simek
2018-04-24 12:27     ` Michal Simek
2018-04-25 12:51 ` Greg Kroah-Hartman

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