drivers: PL011: allow avoiding UART enabling/disabling

The SBSA UART should not be enabled or disabled (it is always on),
and consequently the spec lacks the UART_CR register.
Add a vendor specific property to skip disabling or enabling of the
UART. This will be used later by the SBSA UART support.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Tested-by: Mark Langsdorf <mlangsdo@redhat.com>
Tested-by: Naresh Bhat <nbhat@cavium.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 12 insertions, 6 deletions

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 7ecf3b380132..3f6b9150e575 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -78,6 +78,7 @@ struct vendor_data {
         bool                    oversampling;
         bool                    dma_threshold;
         bool                    cts_event_workaround;
+        bool                    always_enabled;
 
         unsigned int (*get_fifosize)(struct amba_device *dev);
 };
@@ -94,6 +95,7 @@ static struct vendor_data vendor_arm = {
         .oversampling           = false,
         .dma_threshold          = false,
         .cts_event_workaround   = false,
+        .always_enabled         = false,
         .get_fifosize           = get_fifosize_arm,
 };
 
@@ -109,6 +111,7 @@ static struct vendor_data vendor_st = {
         .oversampling           = true,
         .dma_threshold          = true,
         .cts_event_workaround   = true,
+        .always_enabled         = false,
         .get_fifosize           = get_fifosize_st,
 };
 
@@ -1958,7 +1961,7 @@ static void
 pl011_console_write(struct console *co, const char *s, unsigned int count)
 {
         struct uart_amba_port *uap = amba_ports[co->index];
-        unsigned int status, old_cr, new_cr;
+        unsigned int status, old_cr = 0, new_cr;
         unsigned long flags;
         int locked = 1;
 
@@ -1975,10 +1978,12 @@ pl011_console_write(struct console *co, const char *s, unsigned int count)
         /*
          *      First save the CR then disable the interrupts
          */
-        old_cr = readw(uap->port.membase + UART011_CR);
-        new_cr = old_cr & ~UART011_CR_CTSEN;
-        new_cr |= UART01x_CR_UARTEN | UART011_CR_TXE;
-        writew(new_cr, uap->port.membase + UART011_CR);
+        if (!uap->vendor->always_enabled) {
+                old_cr = readw(uap->port.membase + UART011_CR);
+                new_cr = old_cr & ~UART011_CR_CTSEN;
+                new_cr |= UART01x_CR_UARTEN | UART011_CR_TXE;
+                writew(new_cr, uap->port.membase + UART011_CR);
+        }
 
         uart_console_write(&uap->port, s, count, pl011_console_putchar);
 
@@ -1989,7 +1994,8 @@ pl011_console_write(struct console *co, const char *s, unsigned int count)
         do {
                 status = readw(uap->port.membase + UART01x_FR);
         } while (status & UART01x_FR_BUSY);
-        writew(old_cr, uap->port.membase + UART011_CR);
+        if (!uap->vendor->always_enabled)
+                writew(old_cr, uap->port.membase + UART011_CR);
 
         if (locked)
                 spin_unlock(&uap->port.lock);