RE: [PATCH v5 2/2] serial:sunplus-uart:Add Sunplus SoC UART Driver

Hammer Hsieh 謝宏孟
2021-12-13T11:37:35Z

Hi, Jiri Slaby:

Thanks for your review.
My response is below in mail.

Best Regards,
Hammer Hsieh

> -----Original Message-----
> From: Jiri Slaby <jirislaby@kernel.org>
> Sent: Monday, December 13, 2021 3:47 PM
> To: Hammer Hsieh <hammerh0314@gmail.com>; gregkh@linuxfoundation.org;
> robh+dt@kernel.org; linux-serial@vger.kernel.org; devicetree@vger.kernel.org;
> linux-kernel@vger.kernel.org; p.zabel@pengutronix.de
> Cc: Wells Lu 呂芳騰 <wells.lu@sunplus.com>; Hammer Hsieh 謝宏孟
> <hammer.hsieh@sunplus.com>
> Subject: Re: [PATCH v5 2/2] serial:sunplus-uart:Add Sunplus SoC UART Driver
>
> On 13. 12. 21, 8:10, Hammer Hsieh wrote:
> > Add Sunplus SoC UART Driver
> >
> > Signed-off-by: Hammer Hsieh <hammer.hsieh@sunplus.com>
>
> ...
>
> > --- /dev/null
> > +++ b/drivers/tty/serial/sunplus-uart.c
>
> ...
>
> > +static void receive_chars(struct uart_port *port) {
> > + unsigned int lsr = readl(port->membase + SUP_UART_LSR);
> > + unsigned int ch, flag;
> > +
> > + do {
> > + ch = readl(port->membase + SUP_UART_DATA);
> > + flag = TTY_NORMAL;
> > + port->icount.rx++;
> > +
> > + if (unlikely(lsr & SUP_UART_LSR_BRK_ERROR_BITS)) {
> > + if (lsr & SUP_UART_LSR_BC) {
> > + lsr &= ~(SUP_UART_LSR_FE | SUP_UART_LSR_PE);
> > + port->icount.brk++;
> > + if (uart_handle_break(port))
> > + goto ignore_char;
> > + } else if (lsr & SUP_UART_LSR_PE) {
> > + port->icount.parity++;
> > + } else if (lsr & SUP_UART_LSR_FE) {
> > + port->icount.frame++;
> > + }
> > +
> > + if (lsr & SUP_UART_LSR_OE)
> > + port->icount.overrun++;
> > +
> > + if (lsr & SUP_UART_LSR_BC)
> > + flag = TTY_BREAK;
> > + else if (lsr & SUP_UART_LSR_PE)
> > + flag = TTY_PARITY;
> > + else if (lsr & SUP_UART_LSR_FE)
> > + flag = TTY_FRAME;
>
> Why do you handle these separately and not above?
>

Indeed, I will modify as below.
if (lsr & SUP_UART_LSR_BC) {
lsr &= ~(SUP_UART_LSR_FE | SUP_UART_LSR_PE);
port->icount.brk++;
flag = TTY_BREAK;
if (uart_handle_break(port))
goto ignore_char;
} else if (lsr & SUP_UART_LSR_PE) {
port->icount.parity++;
flag = TTY_PARITY;
} else if (lsr & SUP_UART_LSR_FE) {
port->icount.frame++;
flag = TTY_FRAME;
}

> > + }
> > +
> > + if (port->ignore_status_mask & SUP_DUMMY_READ)
> > + goto ignore_char;
> > +
> > + if (uart_handle_sysrq_char(port, ch))
> > + goto ignore_char;
> > +
> > + uart_insert_char(port, lsr, SUP_UART_LSR_OE, ch, flag);
> > +
> > +ignore_char:
> > + lsr = readl(port->membase + SUP_UART_LSR);
> > + } while (lsr & SUP_UART_LSR_RX);
> > +
> > + tty_flip_buffer_push(&port->state->port);
> > +}
> > +
> > +static irqreturn_t sunplus_uart_irq(int irq, void *args) {
> > + struct uart_port *port = (struct uart_port *)args;
>
> No need to cast here.
>

Ok, will modify it.

> > + unsigned int isc = readl(port->membase + SUP_UART_ISC);
>
> Shouldn't this be under the spinlock?
>
> And "if (!isc) return IRQ_NONE"?
>

Will modify it as below.
Spin_lock()
isc = readl(port->membase + SUP_UART_ISC);
if (!isc) return IRQ_NONE;
if(isc&RX) receive_chars();
if(isc&TX) transmit_chars();
Spin_unlock()

> > + spin_lock(&port->lock);
> > +
> > + if (isc & SUP_UART_ISC_RX)
> > + receive_chars(port);
> > +
> > + if (isc & SUP_UART_ISC_TX)
> > + transmit_chars(port);
> > +
> > + spin_unlock(&port->lock);
> > +
> > + return IRQ_HANDLED;
> > +}
> > +
> > +static int sunplus_startup(struct uart_port *port) {
> > + unsigned long flags;
> > + unsigned int isc;
> > + int ret;
> > +
> > + ret = request_irq(port->irq, sunplus_uart_irq, 0, "sunplus_uart",
> > +port);
>
> Cannot the interrupt be shared?
>

Each UART have its own hardware interrupt in Sunplus SP7021 SoC.
No need to set IRQF_SHARED for serial driver.

> > + if (ret)
> > + return ret;
> > +
> > + spin_lock_irqsave(&port->lock, flags);
> > +
> > + isc |= SUP_UART_ISC_RXM;
> > + writel(isc, port->membase + SUP_UART_ISC);
> > +
> > + spin_unlock_irqrestore(&port->lock, flags);
> > +
> > + return 0;
> > +}
> > +
> > +static void sunplus_shutdown(struct uart_port *port) {
> > + unsigned long flags;
> > +
> > + spin_lock_irqsave(&port->lock, flags);
> > + writel(0, port->membase + SUP_UART_ISC);
>
> What bus is this -- posting?
>

Here just clear interrupt.
Not really understand your comment?

> > + spin_unlock_irqrestore(&port->lock, flags);
> > +
> > + free_irq(port->irq, port);
> > +}
>
> ...
>
> > +static void sunplus_release_port(struct uart_port *port) { }
> > +
> > +static int sunplus_request_port(struct uart_port *port) {
> > + return 0;
> > +}
>
> These two are optional -- no need to provide them.
>

Ok, thanks.
I will remove these two functions.

> regards,
> --
> js
> suse labs