[PATCH] rockchip: efuse: fix rk3399 reading multiple values

[John Keeping]

On Mon, Apr 17, 2023 at 05:39:24PM +0000, Jonas Karlman wrote:
> On 2023-04-17 18:09, John Keeping wrote:
> > Update rk3399 to match the pattern in the other device-specific
> > implementations to ensure the previous address is cleared when reading
> > multiple blocks.
> 
> Does this fix a real issue for you?
> 
> Compared to the other device-specific implementations this reg behaves
> differently on RK3399. The addr field is not read back, or it gets
> auto-cleared when EFUSE_STROBE is cleared, the use of clrsetbits_le32
> may mislead that this reg holds the addr value from prior iteration.

I don't have an RK3399 to test with, but I spotted this when
experimenting with RK3288's secure efuse which has a similar layout to
the RK3399 efuses.

Having looked through the RK3399 TRM, I can't see anything about the
address auto-clearing and the documentation for redundancy read mode
requiring two strobe cycles suggests that the address is preserved.

Howe are you testing reads?  dump_efuse only reads one block at a time
so it isn't sufficient to trigger an issue here as there is an
unconditional write to EFUSE_CTRL before this loop.

> > 
> > Signed-off-by: John Keeping <john at metanate.com>
> > ---
> >  drivers/misc/rockchip-efuse.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/misc/rockchip-efuse.c b/drivers/misc/rockchip-efuse.c
> > index 2f96b79ea4..d302271239 100644
> > --- a/drivers/misc/rockchip-efuse.c
> > +++ b/drivers/misc/rockchip-efuse.c
> > @@ -207,8 +207,8 @@ static int rockchip_rk3399_efuse_read(struct udevice *dev, int offset,
> >  	udelay(1);
> >  
> >  	while (size--) {
> > -		setbits_le32(efuse->base + EFUSE_CTRL,
> > -			     EFUSE_STROBE | RK3399_ADDR(offset++));
> > +		clrsetbits_le32(efuse->base + EFUSE_CTRL, RK3399_A_MASK,
> > +				EFUSE_STROBE | RK3399_ADDR(offset++));
> >  		udelay(1);
> >  		*buffer++ = readl(efuse->base + EFUSE_DOUT);
> >  		clrbits_le32(efuse->base + EFUSE_CTRL, EFUSE_STROBE);
>