linux-kernel - Re: [PATCH 2/2] serial: imx: Add more comments on port lock status

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Message-ID: <2200890.irdbgypaU6@steina-w>
Date: Fri, 13 Sep 2024 11:17:04 +0200
From: Alexander Stein <alexander.stein@...tq-group.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>, Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, Pengutronix Kernel Team <kernel@...gutronix.de>, Fabio Estevam <festevam@...il.com>, John Ogness <john.ogness@...uxtronix.de>, linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org, imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, Esben Haabendal <esben@...nix.com>, Esben Haabendal <esben@...nix.com>
Subject: Re: [PATCH 2/2] serial: imx: Add more comments on port lock status

Hi,

Am Freitag, 13. September 2024, 10:39:50 CEST schrieb Esben Haabendal:
> Comments regarding status of port.lock on internal functions is useful when
> reviewing correct handling of registers that must be protected by this
> lock.
> 
> Signed-off-by: Esben Haabendal <esben@...nix.com>
> ---
>  drivers/tty/serial/imx.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index efa3eb3a2c57..bea4510743ef 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -370,6 +370,7 @@ static void imx_uart_soft_reset(struct imx_port *sport)
>  	sport->idle_counter = 0;
>  }
>  
> +/* called with port.lock taken and irqs off */
>  static void imx_uart_disable_loopback_rs485(struct imx_port *sport)
>  {
>  	unsigned int uts;

I think you are referring to sport.lock. On the other hand, instead of
just adding comments, wouldn't it be better to make it explicit?
Adding 
> lockdep_assert_held(&sport->port->lock);
and/or sparse annoations
> __must_hold(&sport->port->lock)

seems more reasonable to me than adding non-enforcing comments.

Best regards,
Alexander

> @@ -470,6 +471,7 @@ static void imx_uart_stop_tx(struct uart_port *port)
>  	}
>  }
>  
> +/* called with port.lock taken and irqs off */
>  static void imx_uart_stop_rx_with_loopback_ctrl(struct uart_port *port, bool loopback)
>  {
>  	struct imx_port *sport = to_imx_port(port);
> @@ -803,6 +805,8 @@ static irqreturn_t imx_uart_txint(int irq, void *dev_id)
>   * issuing soft reset to the UART (just stop/start of RX does not help). Note
>   * that what we do here is sending isolated start bit about 2.4 times shorter
>   * than it is to be on UART configured baud rate.
> + *
> + * Called with port.lock taken and irqs off.
>   */
>  static void imx_uart_check_flood(struct imx_port *sport, u32 usr2)
>  {
> @@ -838,6 +842,7 @@ static void imx_uart_check_flood(struct imx_port *sport, u32 usr2)
>  	}
>  }
>  
> +/* called with port.lock taken and irqs off */
>  static irqreturn_t __imx_uart_rxint(int irq, void *dev_id)
>  {
>  	struct imx_port *sport = dev_id;
> @@ -916,6 +921,7 @@ static void imx_uart_clear_rx_errors(struct imx_port *sport);
>  /*
>   * We have a modem side uart, so the meanings of RTS and CTS are inverted.
>   */
> +/* called with port.lock taken and irqs off */
>  static unsigned int imx_uart_get_hwmctrl(struct imx_port *sport)
>  {
>  	unsigned int tmp = TIOCM_DSR;
> @@ -938,6 +944,8 @@ static unsigned int imx_uart_get_hwmctrl(struct imx_port *sport)
>  
>  /*
>   * Handle any change of modem status signal since we were last called.
> + *
> + * Called with port.lock taken and irqs off.
>   */
>  static void imx_uart_mctrl_check(struct imx_port *sport)
>  {
> @@ -1277,6 +1285,7 @@ static int imx_uart_start_rx_dma(struct imx_port *sport)
>  	return 0;
>  }
>  
> +/* called with port.lock taken and irqs off */
>  static void imx_uart_clear_rx_errors(struct imx_port *sport)
>  {
>  	struct tty_port *port = &sport->port.state->port;
> @@ -1407,6 +1416,7 @@ static int imx_uart_dma_init(struct imx_port *sport)
>  	return ret;
>  }
>  
> +/* called with port.lock taken and irqs off */
>  static void imx_uart_enable_dma(struct imx_port *sport)
>  {
>  	u32 ucr1;
> 
> 


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