2020-04-09 06:27:41

by Raviteja Narayanam

Subject: [PATCH v2 0/2] serial: uartps: Add tx_empty checks

This patch series does the following:
Use cdns_uart_tx_empty function in the driver.
Wait for empty.

v2:
Modified the wait in console setup and used cdns_uart_tx_empty function
in console_write as suggested by Maarten.

Raviteja Narayanam (2):
serial: uartps: Wait for tx_empty in console setup
serial: uartps: Use cdns_uart_tx_empty in console_write

drivers/tty/serial/xilinx_uartps.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

--
2.7.4

2020-04-09 06:27:58

by Raviteja Narayanam

Subject: [PATCH v2 2/2] serial: uartps: Use cdns_uart_tx_empty in console_write

Instead of accessing the registers and checking for tx_empty,
use cdns_uart_tx_empty in cdns_uart_console_write function.

Signed-off-by: Raviteja Narayanam <[email protected]>
---
drivers/tty/serial/xilinx_uartps.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 0bf946b..042aa6f 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1233,9 +1233,7 @@ static void cdns_uart_console_write(struct console *co, const char *s,
writel(ctrl, port->membase + CDNS_UART_CR);

uart_console_write(port, s, count, cdns_uart_console_putchar);
- while ((readl(port->membase + CDNS_UART_SR) &
- (CDNS_UART_SR_TXEMPTY | CDNS_UART_SR_TACTIVE)) !=
- CDNS_UART_SR_TXEMPTY)
+ while (cdns_uart_tx_empty(port) != TIOCSER_TEMT)
cpu_relax();

/* restore interrupt state */
--
2.7.4

2020-04-09 06:28:04

by Raviteja Narayanam

Subject: [PATCH v2 1/2] serial: uartps: Wait for tx_empty in console setup

On some platforms, the log is corrupted while console is being
registered. It is observed that when set_termios is called, there
are still some bytes in the FIFO to be transmitted.

So, wait for tx_empty inside cdns_uart_console_setup before calling
set_termios.

Signed-off-by: Raviteja Narayanam <[email protected]>
---
drivers/tty/serial/xilinx_uartps.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 6b26f76..0bf946b 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1260,6 +1260,7 @@ static int cdns_uart_console_setup(struct console *co, char *options)
int bits = 8;
int parity = 'n';
int flow = 'n';
+ unsigned long time_out;

if (!port->membase) {
pr_debug("console on " CDNS_UART_TTY_NAME "%i not present\n",
@@ -1270,6 +1271,13 @@ static int cdns_uart_console_setup(struct console *co, char *options)
if (options)
uart_parse_options(options, &baud, &parity, &bits, &flow);

+ /* Wait for tx_empty before setting up the console */
+ time_out = jiffies + usecs_to_jiffies(TX_TIMEOUT);
+
+ while (time_before(jiffies, time_out) &&
+ cdns_uart_tx_empty(port) != TIOCSER_TEMT)
+ cpu_relax();
+
return uart_set_options(port, co, baud, parity, bits, flow);
}
#endif /* CONFIG_SERIAL_XILINX_PS_UART_CONSOLE */
--
2.7.4

2020-04-13 10:11:46

by Shubhrajyoti Datta

Subject: Re: [PATCH v2 0/2] serial: uartps: Add tx_empty checks

Hi Raviteja,
thanks for the patch.

On Thu, Apr 9, 2020 at 11:59 AM Raviteja Narayanam
<[email protected]> wrote:
>
> This patch series does the following:
> Use cdns_uart_tx_empty function in the driver.
> Wait for empty.
>
> v2:
> Modified the wait in console setup and used cdns_uart_tx_empty function
> in console_write as suggested by Maarten.
>
Reviewed-by: Shubhrajyoti Datta <[email protected]>

> Raviteja Narayanam (2):
> serial: uartps: Wait for tx_empty in console setup
> serial: uartps: Use cdns_uart_tx_empty in console_write
>
> drivers/tty/serial/xilinx_uartps.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> --
> 2.7.4
>