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Subject[PATCH 2/2] serial: mvebu-uart: initialize over sampling stack register
Date
The baudrate derivation relies on the state of the programmable over
sampling stack (OSAMP register) being empty, while never initializing
it.

Set all the fields of this register to 0 (except reserved areas) to
ensure a x16 divisor, as assumed by the driver.

The suspend/resume callbacks are untouched because they already
save/restore correctly this register.

Suggested-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
drivers/tty/serial/mvebu-uart.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c
index df6e4d8cdbd6..231f751d1ef4 100644
--- a/drivers/tty/serial/mvebu-uart.c
+++ b/drivers/tty/serial/mvebu-uart.c
@@ -73,6 +73,7 @@

#define UART_OSAMP 0x14
#define OSAMP_DEFAULT_DIVISOR 16
+#define OSAMP_DIVISORS_MASK 0x3F3F3F3F

#define MVEBU_NR_UARTS 2

@@ -446,7 +447,7 @@ static int mvebu_uart_baud_rate_set(struct uart_port *port, unsigned int baud)
{
struct mvebu_uart *mvuart = to_mvuart(port);
unsigned int d_divisor, m_divisor;
- u32 brdv;
+ u32 brdv, osamp;

if (IS_ERR(mvuart->clk))
return -PTR_ERR(mvuart->clk);
@@ -469,6 +470,10 @@ static int mvebu_uart_baud_rate_set(struct uart_port *port, unsigned int baud)
brdv |= d_divisor;
writel(brdv, port->membase + UART_BRDV);

+ osamp = readl(port->membase + UART_OSAMP);
+ osamp &= ~OSAMP_DIVISORS_MASK;
+ writel(osamp, port->membase + UART_OSAMP);
+
return 0;
}

--
2.19.1
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