Re: [PATCH] serial: 8250_omap: Implementation of Errata i2310

[Kumar, Udit]

On 6/14/2024 1:58 PM, Ilpo Järvinen wrote:
> On Fri, 14 Jun 2024, Udit Kumar wrote:
>
> > As per Errata i2310[0], Erroneous timeout can be triggered,
> > if this Erroneous interrupt is not cleared then it may leads
> > to strom of interrupts, therefore apply Errata i2310 solution.
> >
> > [0] https://www.ti.com/lit/pdf/sprz536 page 23
> >
> > Signed-off-by: Udit Kumar <u-kumar1@xxxxxx>
> > ---
> >   drivers/tty/serial/8250/8250_omap.c | 25 ++++++++++++++++++++-----
> >   1 file changed, 20 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
> > index 170639d12b2a..38eb639f78d3 100644
> > --- a/drivers/tty/serial/8250/8250_omap.c
> > +++ b/drivers/tty/serial/8250/8250_omap.c
> > @@ -115,6 +115,10 @@
> >   /* RX FIFO occupancy indicator */
> >   #define UART_OMAP_RX_LVL		0x19
> >   
> > +/* Timeout Low and High */
> > +#define UART_OMAP_TO_L                 0x26
> > +#define UART_OMAP_TO_H                 0x27
> > +
> >   /*
> >    * Copy of the genpd flags for the console.
> >    * Only used if console suspend is disabled
> > @@ -663,13 +667,24 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
> >   
> >   	/*
> >   	 * On K3 SoCs, it is observed that RX TIMEOUT is signalled after
> > -	 * FIFO has been drained, in which case a dummy read of RX FIFO
> > -	 * is required to clear RX TIMEOUT condition.
> > +	 * FIFO has been drained or erroneously.
> > +	 * So apply solution of Errata i2310 as mentioned in
> > +	 * https://www.ti.com/lit/pdf/sprz536
> >   	 */
> >   	if (priv->habit & UART_RX_TIMEOUT_QUIRK &&
> > -	    (iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT &&
> > -	    serial_port_in(port, UART_OMAP_RX_LVL) == 0) {
> > -		serial_port_in(port, UART_RX);
> > +		(iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT) {
> > +		unsigned char efr2, timeout_h, timeout_l;
> > +
> > +		efr2 = serial_in(up, UART_OMAP_EFR2);
> > +		timeout_h = serial_in(up, UART_OMAP_TO_H);
> > +		timeout_l = serial_in(up, UART_OMAP_TO_L);
> > +		serial_out(up, UART_OMAP_TO_H, 0xFF);
> > +		serial_out(up, UART_OMAP_TO_L, 0xFF);
> > +		serial_out(up, UART_OMAP_EFR2, 0x1);
> Eh, this doesn't match the workaround in the errata???
>
> Also, don't use literals but name the bits with defines (for the correct
> bit there's probably a pre-existing define but it's not named as good as
> it could be, I'd say it should be named as
> UART_OMAP_EFR2_TIMEOUT_PERIODIC).


Thanks, will address in v2.


> > +		serial_in(up, UART_IIR);
> > +		serial_out(up, UART_OMAP_EFR2, efr2);
> > +		serial_out(up, UART_OMAP_TO_H, timeout_h);
> > +		serial_out(up, UART_OMAP_TO_L, timeout_l);