On Tue, Sep 06, 2022 at 09:04:05AM +0800, Peng Fan wrote: > > > On 9/5/2022 5:58 PM, Johannes Schneider wrote: > > on imx8(mm) the RXDMUXSEL needs to be set for data going over the wire > > (as observable on a connected 'scope) to actually make it into the > > RXFIFO > > > > the reference manual is not overly clear about this, and only > > mentiones that "UCR3_RXDMUXSEL should always be set." - and since the > > CR3 register reverts to its reset values after setting the baudrate, > > setting this bit is done during '_mxc_serial_setbgr' > > > > Signed-off-by: Johannes Schneider <[email protected]> > > > > --- > > > > (no changes since v1) > > > > drivers/serial/serial_mxc.c | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/drivers/serial/serial_mxc.c b/drivers/serial/serial_mxc.c > > index 70a0e5e919..5f283cc635 100644 > > --- a/drivers/serial/serial_mxc.c > > +++ b/drivers/serial/serial_mxc.c > > @@ -61,6 +61,11 @@ > > #define UCR3_AWAKEN (1<<4) /* Async wake interrupt enable */ > > #define UCR3_REF25 (1<<3) /* Ref freq 25 MHz */ > > #define UCR3_REF30 (1<<2) /* Ref Freq 30 MHz */ > > + > > +//imx8 names these bitsfields instead: > > +#define UCR3_DTRDEN BIT(3) /* bit not used in this chip */ > > +#define UCR3_RXDMUXSEL BIT(2) /* RXD muxed input selected; 'should > > always be set' */ > > + > > #define UCR3_INVT (1<<1) /* Inverted Infrared transmission */ > > #define UCR3_BPEN (1<<0) /* Preset registers enable */ > > #define UCR4_CTSTL_32 (32<<10) /* CTS trigger level (32 chars) */ > > @@ -176,6 +181,12 @@ static void _mxc_serial_setbrg(struct mxc_uart *base, > > unsigned long clk, > > writel(UCR2_WS | UCR2_IRTS | UCR2_RXEN | UCR2_TXEN | UCR2_SRST, > > &base->cr2); > > + > > + // setting the baudrate triggers a reset, returning cr3 to its > > + // reset value but UCR3_RXDMUXSEL "should always be set." > > + // according to the imx8 reference-manual > > + writel(readl(&base->cr3) | UCR3_RXDMUXSEL, &base->cr3); > > Please fix comment format.
We allow '//' style comments, just like the linux kernel does these days. There should be a space before the "imx8" in the first hunk here. -- Tom
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