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Date: Mon, 29 Aug 2022 09:27:01 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Pali Rohár <pali@...nel.org>
Cc: gregkh@...uxfoundation.org, linux-serial@...r.kernel.org,
linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH 3/3] tty: serial: use uart_port_tx_limit() helper
On 11. 04. 22, 13:51, Pali Rohár wrote:
> On Monday 11 April 2022 12:54:05 Jiri Slaby wrote:
>> uart_port_tx_limit() is a new helper to send characters to the device.
>> Use it in these drivers.
>>
>> It means we have to define two new uart hooks: tx_ready() and put_char()
>> to do the real job now.
>>
>> And mux.c also needs to define tx_done(). But I'm not sure if the driver
>> really wants to wait for all the characters to dismiss from the HW fifo
>> at this code point. Hence I marked this as FIXME.
>>
>> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
>> Cc: Russell King <linux@...linux.org.uk>
>> Cc: Florian Fainelli <f.fainelli@...il.com>
>> Cc: bcm-kernel-feedback-list@...adcom.com
>> Cc: "Pali Rohár" <pali@...nel.org>
>> Cc: Kevin Cernekee <cernekee@...il.com>
>> Cc: Palmer Dabbelt <palmer@...belt.com>
>> Cc: Paul Walmsley <paul.walmsley@...ive.com>
>> Cc: Orson Zhai <orsonzhai@...il.com>
>> Cc: Baolin Wang <baolin.wang7@...il.com>
>> Cc: Chunyan Zhang <zhang.lyra@...il.com>
>> Cc: Patrice Chotard <patrice.chotard@...s.st.com>
>> Cc: linux-riscv@...ts.infradead.org
>> ---
>> drivers/tty/serial/21285.c | 40 +++++++--------------
>> drivers/tty/serial/altera_jtaguart.c | 43 ++++++----------------
>> drivers/tty/serial/amba-pl010.c | 40 ++++-----------------
>> drivers/tty/serial/apbuart.c | 37 ++++---------------
>> drivers/tty/serial/bcm63xx_uart.c | 48 ++++++-------------------
>> drivers/tty/serial/mux.c | 48 ++++++++-----------------
>> drivers/tty/serial/mvebu-uart.c | 47 +++++++-----------------
>> drivers/tty/serial/omap-serial.c | 53 +++++++---------------------
>> drivers/tty/serial/pxa.c | 43 +++++-----------------
>> drivers/tty/serial/rp2.c | 36 ++++++-------------
>> drivers/tty/serial/serial_txx9.c | 40 ++++-----------------
>> drivers/tty/serial/sifive.c | 48 ++++---------------------
>> drivers/tty/serial/sprd_serial.c | 41 ++++-----------------
>> drivers/tty/serial/st-asc.c | 51 ++++----------------------
>> drivers/tty/serial/vr41xx_siu.c | 42 ++++------------------
>> 15 files changed, 143 insertions(+), 514 deletions(-)
> ...
>> diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c
>> index 0429c2a54290..3d07ab9eb15e 100644
>> --- a/drivers/tty/serial/mvebu-uart.c
>> +++ b/drivers/tty/serial/mvebu-uart.c
>> @@ -194,6 +194,16 @@ static unsigned int mvebu_uart_tx_empty(struct uart_port *port)
>> return (st & STAT_TX_EMP) ? TIOCSER_TEMT : 0;
>> }
>>
>> +static bool mvebu_uart_tx_ready(struct uart_port *port)
>> +{
>> + return !(readl(port->membase + UART_STAT) & STAT_TX_FIFO_FUL);
>
> mvebu-uart.c driver in its tx_ready function should probably use
> STAT_TX_RDY macro (access to STAT_TX_RDY bit in register).
>
> Documentation for UART1 (STD) about this bit says:
>
> This bit is set when TRANS_HLD (our UART_TSH macro) is empty and ready
> for the CPU to write the next character to be transmitted out. The TSR
> can still shift out the previous character when this bit is set. This
> bit is cleared when the CPU writes to TRANS_HLD.
>
> For UART2 (EXT) there is just information: UART Tx Ready for 1 Byte
> Write. UART2 (EXT) has also bit (bit 5) which indicates that CPU can
> load 4 bytes, but seems that this is not used by mvebu-uart.c driver.
>
> Macro STAT_TX_RDY() is polled also in wait_for_xmitr() function.
Hi,
so care to send fixes for the two issues :)? The series is not meant to
change behavior...
>> +}
>> +
>> +static void mvebu_uart_put_char(struct uart_port *port, unsigned char ch)
>> +{
>> + writel(ch, port->membase + UART_TSH(port));
>> +}
>> +
>> static unsigned int mvebu_uart_get_mctrl(struct uart_port *port)
>> {
>> return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
>> @@ -324,40 +334,7 @@ static void mvebu_uart_rx_chars(struct uart_port *port, unsigned int status)
>>
>> static void mvebu_uart_tx_chars(struct uart_port *port, unsigned int status)
>> {
>> - struct circ_buf *xmit = &port->state->xmit;
>> - unsigned int count;
>> - unsigned int st;
>> -
>> - if (port->x_char) {
>> - writel(port->x_char, port->membase + UART_TSH(port));
>> - port->icount.tx++;
>> - port->x_char = 0;
>> - return;
>> - }
>> -
>> - if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
>> - mvebu_uart_stop_tx(port);
>> - return;
>> - }
>> -
>> - for (count = 0; count < port->fifosize; count++) {
>> - writel(xmit->buf[xmit->tail], port->membase + UART_TSH(port));
>> - xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
>> - port->icount.tx++;
>> -
>> - if (uart_circ_empty(xmit))
>> - break;
>> -
>> - st = readl(port->membase + UART_STAT);
>> - if (st & STAT_TX_FIFO_FUL)
>> - break;
>
> I see that driver here currently use STAT_TX_FIFO_FUL for checking if it
> can do next iteration and write next character to UART_TSH.
>
> Documentation about this bit says that ... the FIFO is full, which is
> indicated by TX_FIFO_FULL. TX_READY status is set as long as the FIFO is
> not full. The Tx ready status is cleared when in THR FIFO is full.
>
> In case driver does not use 4 byte loads for UART2, TX_READY and
> !TX_FIFO_FULL are probably same...
>
> Anyway, mvebu_uart_tx_chars() is called from the mvebu_uart_tx_isr()
> interrupt handler which is registered for CTRL_RX_RDY_INT interrupt
> which should signal when TX_READY is set.
>
>> - }
>> -
>> - if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
>> - uart_write_wakeup(port);
>> -
>> - if (uart_circ_empty(xmit))
>> - mvebu_uart_stop_tx(port);
>> + uart_port_tx_limit(port, port->fifosize);
>> }
>>
>> static irqreturn_t mvebu_uart_isr(int irq, void *dev_id)
>> @@ -654,6 +631,8 @@ static void mvebu_uart_put_poll_char(struct uart_port *port, unsigned char c)
>>
>> static const struct uart_ops mvebu_uart_ops = {
>> .tx_empty = mvebu_uart_tx_empty,
>> + .tx_ready = mvebu_uart_tx_ready,
>> + .put_char = mvebu_uart_put_char,
>> .set_mctrl = mvebu_uart_set_mctrl,
>> .get_mctrl = mvebu_uart_get_mctrl,
>> .stop_tx = mvebu_uart_stop_tx,
thanks,
--
js
suse labs
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