Re: [PATCH] PCI: apple: Fix REFCLK1 enable/poll logic

[Hector Martin]

On 01/12/2021 01.49, Lorenzo Pieralisi wrote:
> On Wed, Nov 17, 2021 at 05:56:12PM +0000, Marc Zyngier wrote:
> > On Wed, 17 Nov 2021 14:00:44 +0000,
> > Hector Martin <marcan@xxxxxxxxx> wrote:
> > > REFCLK1 has req/ack bits just like REFCLK0
> > >
> > > Signed-off-by: Hector Martin <marcan@xxxxxxxxx>
> > > ---
> > >   drivers/pci/controller/pcie-apple.c | 7 ++++---
> > >   1 file changed, 4 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c
> > > index b665d29af77a..420c291a5c68 100644
> > > --- a/drivers/pci/controller/pcie-apple.c
> > > +++ b/drivers/pci/controller/pcie-apple.c
> > > @@ -42,8 +42,9 @@
> > >   #define   CORE_FABRIC_STAT_MASK		0x001F001F
> > >   #define CORE_LANE_CFG(port)		(0x84000 + 0x4000 * (port))
> > >   #define   CORE_LANE_CFG_REFCLK0REQ	BIT(0)
> > > -#define   CORE_LANE_CFG_REFCLK1		BIT(1)
> > > +#define   CORE_LANE_CFG_REFCLK1REQ	BIT(1)
> > >   #define   CORE_LANE_CFG_REFCLK0ACK	BIT(2)
> > > +#define   CORE_LANE_CFG_REFCLK1ACK	BIT(3)
> > >   #define   CORE_LANE_CFG_REFCLKEN	(BIT(9) | BIT(10))
> > >   #define CORE_LANE_CTL(port)		(0x84004 + 0x4000 * (port))
> > >   #define   CORE_LANE_CTL_CFGACC		BIT(15)
> > > @@ -481,9 +482,9 @@ static int apple_pcie_setup_refclk(struct apple_pcie *pcie,
> > >   	if (res < 0)
> > >   		return res;
> > >   
> > > -	rmw_set(CORE_LANE_CFG_REFCLK1, pcie->base + CORE_LANE_CFG(port->idx));
> > > +	rmw_set(CORE_LANE_CFG_REFCLK1REQ, pcie->base + CORE_LANE_CFG(port->idx));
> > >   	res = readl_relaxed_poll_timeout(pcie->base + CORE_LANE_CFG(port->idx),
> > > -					 stat, stat & CORE_LANE_CFG_REFCLK1,
> > > +					 stat, stat & CORE_LANE_CFG_REFCLK1ACK,
> > >   					 100, 50000);
> > >   
> > >   	if (res < 0)
> > > --
> > > 2.33.0
> >
> > Fixes: 1e33888fbe44 ("PCI: apple: Add initial hardware bring-up")
> > Acked-by: Marc Zyngier <maz@xxxxxxxxxx>
>
> Hi Hector, Bjorn,
>
> if this is a fix we can aim at one of the upcoming -rcX.
>
> It would be nicer though to explain a bit better what it is
> fixing in the commit log (and what's broken if we don't merge it),
> as it stands it is a bit terse.

I don't think anything is broken per se, it still works without this 
patch (probably because the refclk gets enabled fast enough that we 
don't have to wait for it); it's just that I think this is the correct 
logic. This is all reverse engineered anyway, so ultimately there is no 
hardware documentation to point to to say what's right and what's wrong...

--
Hector Martin (marcan@xxxxxxxxx)
Public Key: https://mrcn.st/pub