Hello,
> The com_read_reg() function returns a uint8_t, which means that only
> the lower 8 bits of the CPR register are returned. So what you need
> here is something like
>
> cpr = bus_space_read_4(sc->sc_iot, sc->sc_ioh, com_cpr << 2);
> sc->sc_fifolen = CPR_FIFO_MODE(cpr) * 16;
> With that change, the Rockchip RK3399 UART reports a 64-byte FIFO,
> which matches the datasheet for that SoC.
okay, fixed.
> What happens on the H6 and H616 with that code? Does it also report a
> non-zero FIFO size? In that case we probably should change the code a
> bit.
Allwinner's chip has no CPR and returns zero value, so that code
results "com0 at simplebus0: DesignWare APB UART, no fifo"
even if (the actual FIFO size is unknwon but) FIFO is implemented.
How about this new diff for com.c? Minimal FIFO size is increased to 16byte
by comment from chrisz@. And FIFO size will be displayed when meaningful
FIFO size is obtained from CPR.
Regards,
--
SASANO Takayoshi (JG1UAA) <u...@mx5.nisiq.net>
Index: com.c
===================================================================
RCS file: /cvs/src/sys/dev/ic/com.c,v
retrieving revision 1.174
diff -u -p -r1.174 com.c
--- com.c 6 May 2021 20:35:21 -0000 1.174
+++ com.c 8 Jan 2022 21:14:44 -0000
@@ -1300,7 +1300,8 @@ void
com_attach_subr(struct com_softc *sc)
{
int probe = 0;
- u_int8_t lcr;
+ u_int8_t lcr, fifo;
+ u_int32_t cpr;
sc->sc_ier = 0;
/* disable interrupts */
@@ -1480,6 +1481,26 @@ com_attach_subr(struct com_softc *sc)
SET(sc->sc_hwflags, COM_HW_FIFO);
sc->sc_fifolen = 256;
break;
+ case COM_UART_DW_APB:
+ printf(": DesignWare APB UART");
+ SET(sc->sc_hwflags, COM_HW_FIFO);
+ cpr = bus_space_read_4(sc->sc_iot, sc->sc_ioh, com_cpr << 2);
+ sc->sc_fifolen = CPR_FIFO_MODE(cpr) * 16;
+ if (sc->sc_fifolen) {
+ printf(", %d byte fifo\n", sc->sc_fifolen);
+ } else {
+ printf("\n");
+ /*
+ * Allwinner H6's DW-APB configuration does not have
+ * CPR register and detect as no fifo.
+ * But this UART has 256 bytes FIFO and disabling FIFO
+ * makes problem; LSR_RXRDY is still set after
+ * reading com_data when FIFO is disabled (errata?).
+ * For workaround, treat as 16 byte FIFO.
+ */
+ sc->sc_fifolen = 16;
+ }
+ break;
default:
panic("comattach: bad fifo type");
}
@@ -1496,10 +1517,13 @@ com_attach_subr(struct com_softc *sc)
}
/* clear and disable fifo */
- com_write_reg(sc, com_fifo, FIFO_RCV_RST | FIFO_XMT_RST);
+ /* DW-APB UART cannot turn off FIFO here (ddb will not work) */
+ fifo = (sc->sc_uarttype == COM_UART_DW_APB) ?
+ (FIFO_ENABLE | FIFO_TRIGGER_1) : 0;
+ com_write_reg(sc, com_fifo, fifo | FIFO_RCV_RST | FIFO_XMT_RST);
if (ISSET(com_read_reg(sc, com_lsr), LSR_RXRDY))
(void)com_read_reg(sc, com_data);
- com_write_reg(sc, com_fifo, 0);
+ com_write_reg(sc, com_fifo, fifo);
sc->sc_mcr = 0;
com_write_reg(sc, com_mcr, sc->sc_mcr);
