Re: [PATCH 5/6] ARM: ks8695, serial: skip manual tx IRQ ack

Greg Ungerer
2019-04-20T02:15:55Z

Hi Arnd,

On 16/4/19 6:24 am, Arnd Bergmann wrote:
> The TX interrupt is marked as edge triggered, so it will
> already be acked by the top-level irq code, and does not
> need the ack in the driver.
>
> Removing this avoids a nasty dependency on the regs-irq.h
> file that is otherwise reserved for the interrupt controller
> driver.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/tty/serial/serial_ks8695.c | 5 -----
> 1 file changed, 5 deletions(-)
>
> diff --git a/drivers/tty/serial/serial_ks8695.c b/drivers/tty/serial/serial_ks8695.c
> index b461d791188c..6c5e9900e69d 100644
> --- a/drivers/tty/serial/serial_ks8695.c
> +++ b/drivers/tty/serial/serial_ks8695.c
> @@ -21,7 +21,6 @@
> #include <asm/mach/irq.h>
>
> #include <mach/regs-uart.h>
> -#include <mach/regs-irq.h>
>
> #if defined(CONFIG_SERIAL_KS8695_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
> #define SUPPORT_SYSRQ
> @@ -52,8 +51,6 @@
> #define UART_GET_BRDR(p) __raw_readl((p)->membase + KS8695_URBD)
> #define UART_PUT_BRDR(p, c) __raw_writel((c), (p)->membase + KS8695_URBD)
>
> -#define KS8695_CLR_TX_INT() __raw_writel(1 << KS8695_IRQ_UART_TX, KS8695_IRQ_VA + KS8695_INTST)
> -
> #define UART_DUMMY_LSR_RX 0x100
> #define UART_PORT_SIZE (KS8695_USR - KS8695_URRB + 4)
>
> @@ -207,7 +204,6 @@ static irqreturn_t ks8695uart_tx_chars(int irq, void *dev_id)
> unsigned int count;
>
> if (port->x_char) {
> - KS8695_CLR_TX_INT();
> UART_PUT_CHAR(port, port->x_char);
> port->icount.tx++;
> port->x_char = 0;
> @@ -221,7 +217,6 @@ static irqreturn_t ks8695uart_tx_chars(int irq, void *dev_id)
>
> count = 16; /* fifo size */
> while (!uart_circ_empty(xmit) && (count-- > 0)) {
> - KS8695_CLR_TX_INT();

I haven't looked at the ks8695 in quite a while...
But I recall that this was very problematic at the time. Without this being
done after each character it was very easy to get the transmitter to "hang" -
and stop wanting to send any more characters.

I'd like to test this before acking.

Regards
Greg

> UART_PUT_CHAR(port, xmit->buf[xmit->tail]);
>
> xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
>