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Subject: Re: [PATCH v3 2/2] tty/serial: Add rx-tx-swap OF option to
 stm32-usart
To:     Martin Devera <devik@eaxlabs.cz>, <linux-kernel@vger.kernel.org>
CC:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Rob Herring <robh+dt@kernel.org>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        "Alexandre Torgue" <alexandre.torgue@st.com>,
        Jiri Slaby <jirislaby@kernel.org>, Le Ray <erwan.leray@st.com>,
        <linux-serial@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-stm32@st-md-mailman.stormreply.com>,
        <linux-arm-kernel@lists.infradead.org>
References: <439a0d7a-cc0e-764b-7ed8-668b5a85f4a7@foss.st.com>
 <20210302131558.19375-1-devik@eaxlabs.cz>
 <20210302131558.19375-2-devik@eaxlabs.cz>
From:   Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Message-ID: <aeefa74e-fa19-6c31-5240-0f14fca89298@foss.st.com>
Date:   Tue, 2 Mar 2021 18:44:26 +0100
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On 3/2/21 2:15 PM, Martin Devera wrote:
> STM32 F7/H7 usarts supports RX & TX pin swapping.
> Add option to turn it on.
> Tested on STM32MP157.
> 
> Signed-off-by: Martin Devera <devik@eaxlabs.cz>
> ---
>  drivers/tty/serial/stm32-usart.c | 11 ++++++++++-
>  drivers/tty/serial/stm32-usart.h |  5 +++++
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
> index b3675cf25a69..d390f7da1441 100644
> --- a/drivers/tty/serial/stm32-usart.c
> +++ b/drivers/tty/serial/stm32-usart.c
> @@ -644,6 +644,12 @@ static int stm32_usart_startup(struct uart_port *port)
>  	if (ret)
>  		return ret;
>  
> +	if (stm32_port->swap) {
> +		val = readl_relaxed(port->membase + ofs->cr2);
> +		val |= USART_CR2_SWAP;
> +		writel_relaxed(val, port->membase + ofs->cr2);
> +	}
> +
>  	/* RX FIFO Flush */
>  	if (ofs->rqr != UNDEF_REG)
>  		stm32_usart_set_bits(port, ofs->rqr, USART_RQR_RXFRQ);
> @@ -758,7 +764,7 @@ static void stm32_usart_set_termios(struct uart_port *port,
>  	cr1 = USART_CR1_TE | USART_CR1_RE;
>  	if (stm32_port->fifoen)
>  		cr1 |= USART_CR1_FIFOEN;
> -	cr2 = 0;
> +	cr2 = stm32_port->swap ? USART_CR2_SWAP : 0;
>  	cr3 = readl_relaxed(port->membase + ofs->cr3);
>  	cr3 &= USART_CR3_TXFTIE | USART_CR3_RXFTCFG_MASK | USART_CR3_RXFTIE
>  		| USART_CR3_TXFTCFG_MASK;
> @@ -1006,6 +1012,9 @@ static int stm32_usart_init_port(struct stm32_port *stm32port,
>  			return stm32port->wakeirq ? : -ENODEV;
>  	}
>  
> +	stm32port->swap = stm32port->info->cfg.has_swap &&
> +		of_property_read_bool(pdev->dev.of_node, "rx-tx-swap");
> +
>  	stm32port->fifoen = stm32port->info->cfg.has_fifo;
>  
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h
> index cb4f327c46db..bd18dd1c1bcd 100644
> --- a/drivers/tty/serial/stm32-usart.h
> +++ b/drivers/tty/serial/stm32-usart.h
> @@ -25,6 +25,7 @@ struct stm32_usart_offsets {
>  struct stm32_usart_config {
>  	u8 uart_enable_bit; /* USART_CR1_UE */
>  	bool has_7bits_data;
> +	bool has_swap;
>  	bool has_wakeup;
>  	bool has_fifo;
>  	int fifosize;
> @@ -55,6 +56,7 @@ struct stm32_usart_info stm32f4_info = {
>  	.cfg = {
>  		.uart_enable_bit = 13,
>  		.has_7bits_data = false,
> +		.has_swap = false,

Hi Martin,

Only one minor comment from me here. No need to add a false (zero)
initialization in this struct. I'm not sure why this is the case for the
has_7bits_data here...

With that fixed, you can add my:
Acked-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>

Thanks for your patch,
Best Regards,
Fabrice

>  		.fifosize = 1,
>  	}
>  };
> @@ -76,6 +78,7 @@ struct stm32_usart_info stm32f7_info = {
>  	.cfg = {
>  		.uart_enable_bit = 0,
>  		.has_7bits_data = true,
> +		.has_swap = true,
>  		.fifosize = 1,
>  	}
>  };
> @@ -97,6 +100,7 @@ struct stm32_usart_info stm32h7_info = {
>  	.cfg = {
>  		.uart_enable_bit = 0,
>  		.has_7bits_data = true,
> +		.has_swap = true,
>  		.has_wakeup = true,
>  		.has_fifo = true,
>  		.fifosize = 16,
> @@ -271,6 +275,7 @@ struct stm32_port {
>  	int last_res;
>  	bool tx_dma_busy;	 /* dma tx busy               */
>  	bool hw_flow_control;
> +	bool swap;		 /* swap RX & TX pins */
>  	bool fifoen;
>  	int wakeirq;
>  	int rdr_mask;		/* receive data register mask */
>