[PATCH 02/12] i3c: mipi-i3c-hci: Fix Hot-Join NACK

[Frank Li]

On Mon, Mar 02, 2026 at 10:42:33AM +0200, Adrian Hunter wrote:
> On 27/02/2026 18:03, Frank Li wrote:
> > On Fri, Feb 27, 2026 at 04:11:39PM +0200, Adrian Hunter wrote:
> >> The MIPI I3C HCI host controller driver does not implement Hot-Join
> >> handling, yet Hot-Join response control defaults to allowing devices to
> >> Hot‑Join the bus.  Configure HC_CONTROL_HOT_JOIN_CTRL to NACK all Hot‑Join
> >> attempts.
> >>
> >> Fixes: 9ad9a52cce282 ("i3c/master: introduce the mipi-i3c-hci driver")
> >> Cc: stable at vger.kernel.org
> >> Signed-off-by: Adrian Hunter <adrian.hunter at intel.com>
> >> ---
> >>  drivers/i3c/master/mipi-i3c-hci/core.c | 6 ++++--
> >>  1 file changed, 4 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
> >> index dbe93df0c70e..4877a321edf9 100644
> >> --- a/drivers/i3c/master/mipi-i3c-hci/core.c
> >> +++ b/drivers/i3c/master/mipi-i3c-hci/core.c
> >> @@ -152,7 +152,8 @@ static int i3c_hci_bus_init(struct i3c_master_controller *m)
> >>  	if (hci->quirks & HCI_QUIRK_RESP_BUF_THLD)
> >>  		amd_set_resp_buf_thld(hci);
> >>
> >> -	reg_set(HC_CONTROL, HC_CONTROL_BUS_ENABLE);
> >> +	/* Enable bus with Hot-Join disabled */
> >> +	reg_set(HC_CONTROL, HC_CONTROL_BUS_ENABLE | HC_CONTROL_HOT_JOIN_CTRL);
> >
> > Can you check varible master->hotjoin? so needn't change it when anable HJ
> > in future?
>
> This is the simplest bug-fix.  There is no need to consider future
> support because anything needed can be done then.

It is also simple if check varible, only one line change

HC_CONTROL_BUS_ENABLE | (master->hotjoin ? 0 : HC_CONTROL_HOT_JOIN_CTRL)

Anyways, it is up to you.

Reviewed-by: Frank Li <Frank.Li at nxp.com>

>
> >
> > Frank
> >
> >>  	dev_dbg(&hci->master.dev, "HC_CONTROL = %#x", reg_read(HC_CONTROL));
> >>
> >>  	return 0;
> >> @@ -764,7 +765,8 @@ static int i3c_hci_runtime_resume(struct device *dev)
> >>
> >>  	hci->io->resume(hci);
> >>
> >> -	reg_set(HC_CONTROL, HC_CONTROL_BUS_ENABLE);
> >> +	/* Enable bus with Hot-Join disabled */
> >> +	reg_set(HC_CONTROL, HC_CONTROL_BUS_ENABLE | HC_CONTROL_HOT_JOIN_CTRL);
> >>
> >>  	return 0;
> >>  }
> >> --
> >> 2.51.0
> >>
> >>
> >> --
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> >> linux-i3c at lists.infradead.org
> >> http://lists.infradead.org/mailman/listinfo/linux-i3c
>
>
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