Re: [PATCH] hw/sd/allwinner-sdhost: report FIFO water level as 1 when data ready

[Peter Maydell]

On Mon, 23 May 2022 at 17:40, Icenowy Zheng <uwu@icenowy.me> wrote:
>
> 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 <uwu@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 <uwu@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 .

Thanks. Since this patch fixes u-boot and is a reasonable
approximation to correct device behaviour assuming we don't
want to bother emulating the FIFO properly, I've applied
it to my target-arm.next tree.

-- PMM