在 2022-05-23星期一的 15:14 +0100，Peter Maydell写道：
> On Fri, 20 May 2022 at 13:42, Icenowy Zheng <u...@icenowy.me> wrote:
> >
> > U-Boot queries the FIFO water level to reduce checking status
> > register
> > when doing PIO SD card operation.
> >
> > Report a FIFO water level of 1 when data is ready, to prevent the
> > code
> > from trying to read 0 words from the FIFO each time.
> >
> > Signed-off-by: Icenowy Zheng <u...@icenowy.me>
> > ---
> > hw/sd/allwinner-sdhost.c | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/hw/sd/allwinner-sdhost.c b/hw/sd/allwinner-sdhost.c
> > index 041e45c680..b66fd9bce7 100644
> > --- a/hw/sd/allwinner-sdhost.c
> > +++ b/hw/sd/allwinner-sdhost.c
> > @@ -114,7 +114,9 @@ enum {
> > };
> >
> > enum {
> > + SD_STAR_FIFO_EMPTY = (1 << 2),
> > SD_STAR_CARD_PRESENT = (1 << 8),
> > + SD_STAR_FIFO_LEVEL_1 = (1 << 17),
> > };
>
> Is there documentation on this hardware available somewhere?
> The Linux kernel driver for it doesn't seem to have a #define
> for this bit 17.
For the specific version on H3,
https://linux-sunxi.org/File:Allwinner_H3_Datasheet_V1.2.pdf .
>
> In an ideal world we'd actually emulate the FIFO itself
> (our pl181 and bcm2835_sdhost models do this, for example).
Interesting, I will check it.
> -- PMM
