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Date: Thu, 26 Mar 2020 00:47:38 +0100 From: Giulio Benetti <giulio.benetti@...ronovasrl.com> To: Heiko Stuebner <heiko@...ech.de>, gregkh@...uxfoundation.org Cc: jslaby@...e.com, andriy.shevchenko@...ux.intel.com, matwey.kornilov@...il.com, linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org, lukas@...ner.de, christoph.muellner@...obroma-systems.com, Heiko Stuebner <heiko.stuebner@...obroma-systems.com> Subject: Re: [PATCH v2 4/7] serial: 8250: Handle implementations not having TEMT interrupt using em485 Hi Heiko, very cleaner way to handle TEMT as a capability! And I've found one thing... Il 26/03/2020 00:14, Heiko Stuebner ha scritto: > From: Giulio Benetti <giulio.benetti@...ronovasrl.com> > > Some 8250 ports have a TEMT interrupt but it's not a part of the 8250 > standard, instead only available on some implementations. > > The current em485 implementation does not work on ports without it. > The only chance to make it work is to loop-read on LSR register. > > So add UART_CAP_TEMT to mark 8250 uarts having this interrupt, > update all current em485 users with that capability and make > the stop_tx function loop-read on uarts not having it. > > Signed-off-by: Giulio Benetti <giulio.benetti@...ronovasrl.com> > [moved to use added UART_CAP_TEMT, use readx_poll_timeout] > Signed-off-by: Heiko Stuebner <heiko.stuebner@...obroma-systems.com> > --- > drivers/tty/serial/8250/8250.h | 1 + > drivers/tty/serial/8250/8250_bcm2835aux.c | 2 +- > drivers/tty/serial/8250/8250_of.c | 2 ++ > drivers/tty/serial/8250/8250_omap.c | 2 +- > drivers/tty/serial/8250/8250_port.c | 25 +++++++++++++++++++---- > 5 files changed, 26 insertions(+), 6 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h > index 52bb21205bb6..770eb00db497 100644 > --- a/drivers/tty/serial/8250/8250.h > +++ b/drivers/tty/serial/8250/8250.h > @@ -82,6 +82,7 @@ struct serial8250_config { > #define UART_CAP_MINI (1 << 17) /* Mini UART on BCM283X family lacks: > * STOP PARITY EPAR SPAR WLEN5 WLEN6 > */ > +#define UART_CAP_TEMT (1 << 18) /* UART has TEMT interrupt */ > > #define UART_BUG_QUOT (1 << 0) /* UART has buggy quot LSB */ > #define UART_BUG_TXEN (1 << 1) /* UART has buggy TX IIR status */ > diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c > index 12d03e678295..3881242424ca 100644 > --- a/drivers/tty/serial/8250/8250_bcm2835aux.c > +++ b/drivers/tty/serial/8250/8250_bcm2835aux.c > @@ -91,7 +91,7 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev) > return -ENOMEM; > > /* initialize data */ > - up.capabilities = UART_CAP_FIFO | UART_CAP_MINI; > + up.capabilities = UART_CAP_FIFO | UART_CAP_MINI | UART_CAP_TEMT; > up.port.dev = &pdev->dev; > up.port.regshift = 2; > up.port.type = PORT_16550; > diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c > index 65e9045dafe6..841f6fcb2878 100644 > --- a/drivers/tty/serial/8250/8250_of.c > +++ b/drivers/tty/serial/8250/8250_of.c > @@ -225,6 +225,8 @@ static int of_platform_serial_probe(struct platform_device *ofdev) > &port8250.overrun_backoff_time_ms) != 0) > port8250.overrun_backoff_time_ms = 0; > > + port8250.capabilities |= UART_CAP_TEMT; > + Shouldn't this be NOT UART_CAP_TEMT set by default? On all other vendor specific files you enable it, I think here you shouldn't enable it too by default. Right? Best regards -- Giulio Benetti CTO MICRONOVA SRL Sede: Via A. Niedda 3 - 35010 Vigonza (PD) Tel. 049/8931563 - Fax 049/8931346 Cod.Fiscale - P.IVA 02663420285 Capitale Sociale € 26.000 i.v. Iscritta al Reg. Imprese di Padova N. 02663420285 Numero R.E.A. 258642 > ret = serial8250_register_8250_port(&port8250); > if (ret < 0) > goto err_dispose; > diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c > index dd69226ce918..d29d5b0cf8c1 100644 > --- a/drivers/tty/serial/8250/8250_omap.c > +++ b/drivers/tty/serial/8250/8250_omap.c > @@ -1140,7 +1140,7 @@ static int omap8250_probe(struct platform_device *pdev) > up.port.regshift = 2; > up.port.fifosize = 64; > up.tx_loadsz = 64; > - up.capabilities = UART_CAP_FIFO; > + up.capabilities = UART_CAP_FIFO | UART_CAP_TEMT; > #ifdef CONFIG_PM > /* > * Runtime PM is mostly transparent. However to do it right we need to a > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c > index 47c059987538..41ad7db6a31e 100644 > --- a/drivers/tty/serial/8250/8250_port.c > +++ b/drivers/tty/serial/8250/8250_port.c > @@ -15,6 +15,7 @@ > #include <linux/moduleparam.h> > #include <linux/ioport.h> > #include <linux/init.h> > +#include <linux/iopoll.h> > #include <linux/console.h> > #include <linux/sysrq.h> > #include <linux/delay.h> > @@ -1520,6 +1521,11 @@ static inline void __do_stop_tx(struct uart_8250_port *p) > serial8250_rpm_put_tx(p); > } > > +static inline int __get_lsr(struct uart_8250_port *p) > +{ > + return serial_in(p, UART_LSR); > +} > + > static inline void __stop_tx(struct uart_8250_port *p) > { > struct uart_8250_em485 *em485 = p->em485; > @@ -1529,11 +1535,22 @@ static inline void __stop_tx(struct uart_8250_port *p) > /* > * To provide required timeing and allow FIFO transfer, > * __stop_tx_rs485() must be called only when both FIFO and > - * shift register are empty. It is for device driver to enable > - * interrupt on TEMT. > + * shift register are empty. If 8250 port supports it, > + * it is for device driver to enable interrupt on TEMT. > + * Otherwise must loop-read until TEMT and THRE flags are set. > */ > - if ((lsr & BOTH_EMPTY) != BOTH_EMPTY) > - return; > + if (p->capabilities & UART_CAP_TEMT) { > + if ((lsr & BOTH_EMPTY) != BOTH_EMPTY) > + return; > + } else { > + int lsr; > + > + if (readx_poll_timeout(__get_lsr, p, lsr, > + (lsr & BOTH_EMPTY) == BOTH_EMPTY, > + 0, 10000) < 0) > + pr_warn("%s: timeout waiting for fifos to empty\n", > + p->port.name); > + } > > __stop_tx_rs485(p); > } >
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