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

[Adrian Hunter]

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.

> 
> 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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