Re: [PATCH v3 2/2] tty/serial: Add rx-tx-swap OF option to stm32-usart

[Martin DEVERA]

On 3/2/21 6:44 PM, Fabrice Gasnier wrote:

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 <de...@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.gasn...@foss.st.com>

The has_7bits_data was what made me a bit unsure. Ok fixed now.
Thank you for your review.

Martin