serial: sccnxp: Adds a delay between sequential read/write cycles

This patch adds a delay between sequential read/write cycles,
to ensure the required minimum inactive time (tRWD). A time value
from the datasheet has been added for each type of supported chips.
The “inline” compiler attribute has been removed from the
read/write functions, simply allow the compiler to control this.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 27 insertions, 5 deletions

diff --git a/drivers/tty/serial/sccnxp.c b/drivers/tty/serial/sccnxp.c
index 339befdd2f4d..c0a68eee4479 100644
--- a/drivers/tty/serial/sccnxp.c
+++ b/drivers/tty/serial/sccnxp.c
@@ -12,6 +12,7 @@
 #endif
 
 #include <linux/clk.h>
+#include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
@@ -103,6 +104,8 @@ struct sccnxp_chip {
         unsigned long           freq_max;
         unsigned int            flags;
         unsigned int            fifosize;
+        /* Time between read/write cycles */
+        unsigned int            trwd;
 };
 
 struct sccnxp_port {
@@ -137,6 +140,7 @@ static const struct sccnxp_chip sc2681 = {
         .freq_max       = 4000000,
         .flags          = SCCNXP_HAVE_IO,
         .fifosize       = 3,
+        .trwd           = 200,
 };
 
 static const struct sccnxp_chip sc2691 = {
@@ -147,6 +151,7 @@ static const struct sccnxp_chip sc2691 = {
         .freq_max       = 4000000,
         .flags          = 0,
         .fifosize       = 3,
+        .trwd           = 150,
 };
 
 static const struct sccnxp_chip sc2692 = {
@@ -157,6 +162,7 @@ static const struct sccnxp_chip sc2692 = {
         .freq_max       = 4000000,
         .flags          = SCCNXP_HAVE_IO,
         .fifosize       = 3,
+        .trwd           = 30,
 };
 
 static const struct sccnxp_chip sc2891 = {
@@ -167,6 +173,7 @@ static const struct sccnxp_chip sc2891 = {
         .freq_max       = 8000000,
         .flags          = SCCNXP_HAVE_IO | SCCNXP_HAVE_MR0,
         .fifosize       = 16,
+        .trwd           = 27,
 };
 
 static const struct sccnxp_chip sc2892 = {
@@ -177,6 +184,7 @@ static const struct sccnxp_chip sc2892 = {
         .freq_max       = 8000000,
         .flags          = SCCNXP_HAVE_IO | SCCNXP_HAVE_MR0,
         .fifosize       = 16,
+        .trwd           = 17,
 };
 
 static const struct sccnxp_chip sc28202 = {
@@ -187,6 +195,7 @@ static const struct sccnxp_chip sc28202 = {
         .freq_max       = 50000000,
         .flags          = SCCNXP_HAVE_IO | SCCNXP_HAVE_MR0,
         .fifosize       = 256,
+        .trwd           = 10,
 };
 
 static const struct sccnxp_chip sc68681 = {
@@ -197,6 +206,7 @@ static const struct sccnxp_chip sc68681 = {
         .freq_max       = 4000000,
         .flags          = SCCNXP_HAVE_IO,
         .fifosize       = 3,
+        .trwd           = 200,
 };
 
 static const struct sccnxp_chip sc68692 = {
@@ -207,24 +217,36 @@ static const struct sccnxp_chip sc68692 = {
         .freq_max       = 4000000,
         .flags          = SCCNXP_HAVE_IO,
         .fifosize       = 3,
+        .trwd           = 200,
 };
 
-static inline u8 sccnxp_read(struct uart_port *port, u8 reg)
+static u8 sccnxp_read(struct uart_port *port, u8 reg)
 {
-        return readb(port->membase + (reg << port->regshift));
+        struct sccnxp_port *s = dev_get_drvdata(port->dev);
+        u8 ret;
+
+        ret = readb(port->membase + (reg << port->regshift));
+
+        ndelay(s->chip->trwd);
+
+        return ret;
 }
 
-static inline void sccnxp_write(struct uart_port *port, u8 reg, u8 v)
+static void sccnxp_write(struct uart_port *port, u8 reg, u8 v)
 {
+        struct sccnxp_port *s = dev_get_drvdata(port->dev);
+
         writeb(v, port->membase + (reg << port->regshift));
+
+        ndelay(s->chip->trwd);
 }
 
-static inline u8 sccnxp_port_read(struct uart_port *port, u8 reg)
+static u8 sccnxp_port_read(struct uart_port *port, u8 reg)
 {
         return sccnxp_read(port, (port->line << 3) + reg);
 }
 
-static inline void sccnxp_port_write(struct uart_port *port, u8 reg, u8 v)
+static void sccnxp_port_write(struct uart_port *port, u8 reg, u8 v)
 {
         sccnxp_write(port, (port->line << 3) + reg, v);
 }