Gemini SoC UART has aditional prescaler register at the same
address as EFR accessible only when DLAB=1.
We need this flag for autodetection to work correctly.
Signed-off-by: Paulius Zaleckas <paulius.zaleckas@xxxxxxxxxxxx>
---
drivers/serial/8250.c | 12 +++++++++---
include/linux/serial_core.h | 1 +
2 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 9ccc563..0ca1f9d 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -843,6 +843,9 @@ static void autoconfig_16550a(struct uart_8250_port *up)
up->port.type = PORT_16550A;
up->capabilities |= UART_CAP_FIFO;
+ if (up->port.flags & UPF_NO_EFR)
+ goto skip_efr;
+
/*
* Check for presence of the EFR when DLAB is set.
* Only ST16C650V1 UARTs pass this test.
@@ -872,6 +875,7 @@ static void autoconfig_16550a(struct uart_8250_port *up)
return;
}
+skip_efr:
/*
* Check for a National Semiconductor SuperIO chip.
* Attempt to switch to bank 2, read the value of the LOOP bit
@@ -1076,9 +1080,11 @@ static void autoconfig(struct uart_8250_port *up, unsigned int probeflags)
* We also initialise the EFR (if any) to zero for later. The
* EFR occupies the same register location as the FCR and IIR.
*/
- serial_outp(up, UART_LCR, 0xBF);
- serial_outp(up, UART_EFR, 0);
- serial_outp(up, UART_LCR, 0);
+ if (!(up->port.flags & UPF_NO_EFR)) {
+ serial_outp(up, UART_LCR, 0xBF);
+ serial_outp(up, UART_EFR, 0);
+ serial_outp(up, UART_LCR, 0);
+ }
serial_outp(up, UART_FCR, UART_FCR_ENABLE_FIFO);
scratch = serial_in(up, UART_IIR) >> 6;
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 3b2f6c0..7a87ba6 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -285,6 +285,7 @@ struct uart_port {
#define UPF_HARDPPS_CD ((__force upf_t) (1 << 11))
#define UPF_LOW_LATENCY ((__force upf_t) (1 << 13))
#define UPF_BUGGY_UART ((__force upf_t) (1 << 14))
+#define UPF_NO_EFR ((__force upf_t) (1 << 15))
#define UPF_MAGIC_MULTIPLIER ((__force upf_t) (1 << 16))
#define UPF_CONS_FLOW ((__force upf_t) (1 << 23))
#define UPF_SHARE_IRQ ((__force upf_t) (1 << 24))
--
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