Re: [PATCH] PCI: spacemit: Ignore link partner PERST on K1

["Encrow Thorne" <encrow.thorne@linux.spacemit.com>]

On Sun Oct 18, 2026 at 12:26 PM CST, Manivannan Sadhasivam wrote:
> On 2026-09-24 10:04 +0800, Encrow Thorne wrote:
>> The K1 PCIe controller and PHY are affected by the PERST signal from
>> the link partner during initialization. With some devices connected,
>> this can prevent host initialization from progressing and cause the
>> system to hang while probing the PCIe controller.
>> 
>> Set PCIE_IGNORE_PERSTN before accessing the DBI registers. When set,
>> this bit makes both the PCIe controller and PHY ignore the PERST
>> signal from the link partner.
>> 
>> This allows host initialization to complete without being affected by
>> the link partner's PERST state.
>> 
>> Signed-off-by: Encrow Thorne <encrow.thorne@linux.spacemit.com>
>> ---
>>  drivers/pci/controller/dwc/pcie-spacemit-k1.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>> 
>> diff --git a/drivers/pci/controller/dwc/pcie-spacemit-k1.c b/drivers/pci/controller/dwc/pcie-spacemit-k1.c
>> index 0564c46e2f48..98f067e1ba81 100644
>> --- a/drivers/pci/controller/dwc/pcie-spacemit-k1.c
>> +++ b/drivers/pci/controller/dwc/pcie-spacemit-k1.c
>> @@ -44,6 +44,7 @@
>>  
>>  #define PCIE_CONTROL_LOGIC			0x0004
>>  #define PCIE_SOFT_RESET			BIT(0)
>> +#define PCIE_IGNORE_PERSTN			BIT(2)
>>  
>>  struct k1_pcie {
>>  	struct dw_pcie pci;
>> @@ -137,6 +138,13 @@ static int k1_pcie_init(struct dw_pcie_rp *pp)
>>  	if (ret)
>>  		return ret;
>>  
>> +	/*
>> +	 * When set to 1, the PCIe controller and PHY ignore the PERST signal
>> +	 * from the link partner in both RC and EP modes.
>> +	 */
>
Hi Mani

> What? PERST# is an output signal to RC and input to Endpoint. PERST# is not
> controlled by the Endpoint, but only by the RC/host.
>
> - Mani

You are right; my earlier wording was misleading.

On K1, the PERST# pad input feeds back into the local controller's
internal reset input even in RC mode. Thus, the RC can reset itself
when asserting PERST# to reset the endpoint.

PCIE_IGNORE_PERSTN masks this input path without affecting the
RC's control of the external PERST# signal.

Regards,
Encrow Thorne