serial: 8250: add serial_in_poll_timeout helper
From: Heiko Stuebner <heiko.stuebner@...> Date: Wed, 18 Mar 2020 15:08:34 +0100
Commit-Message
In cases where a serial register needs to be polled until a specific state, this should have a timeout as noted in the thread bringing em485 support to 8250_dw. To not re-implement timeout handling in each case, add a helper modelled after readx_poll_timeout / regmap_read_poll_timeout to facilitate this. Signed-off-by: Heiko Stuebner <heiko.stuebner@...>
Patch-Comment
drivers/tty/serial/8250/8250.h | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+)
Statistics
- 34 lines added
- 0 lines removed
Changes
------------------------ drivers/tty/serial/8250/8250.h ------------------------
index 33ad9d6de532..50a4c174410d 100644
@@ -118,6 +118,40 @@ static inline void serial_out(struct uart_8250_port *up, int offset, int value)
up->port.serial_out(&up->port, offset, value);
}
+/**
+ * serial_in_poll_timeout - Poll until a condition is met or a timeout occurs
+ *
+ * @port: uart_8250_port to read from
+ * @offs: Offset to poll
+ * @val: Integer variable to read the value into
+ * @cond: Break condition (usually involving @val)
+ * @timeout_us: Timeout in us, 0 means never timeout
+ *
+ * Returns 0 on success and -ETIMEDOUT upon a timeout or the serial_in
+ * error return value in case of a error read.
+ *
+ * This is modelled after the readx_poll_timeout macros in linux/iopoll.h.
+ */
+#define serial_in_poll_timeout(port, offs, val, cond, timeout_us) \
+({ \
+ u64 __timeout_us = (timeout_us); \
+ ktime_t __timeout = ktime_add_us(ktime_get(), __timeout_us); \
+ for (;;) { \
+ val = serial_in((port), (offs)); \
+ if (val < 0) \
+ break; \
+ if (cond) \
+ break; \
+ if ((__timeout_us) && \
+ ktime_compare(ktime_get(), __timeout) > 0) { \
+ val = serial_in((port), (offs)); \
+ break; \
+ } \
+ cpu_relax(); \
+ } \
+ (val < 0) ? val : ((cond) ? 0 : -ETIMEDOUT); \
+})
+
void serial8250_clear_and_reinit_fifos(struct uart_8250_port *p);
static inline int serial_dl_read(struct uart_8250_port *up)