Re: [PATCH v4 2/2] PCI: cadence: Add debugfs property to provide LTSSM status of the PCIe link

[Hans Zhang <18255117159@163.com>]

On 5/13/26 16:34, Aksh Garg wrote:

>>>
>>
>> The above LTSSM states are internal LTSSM encoding states and may not 
>> be available for software to use.
>> The LTSSM states in the document pointed by Aksh (TI Soc) are the 
>> states  available in all cadence controllers.
> 
> Is this true for HPA IPs as well? The test performed by Hans:
> root@orangepi6plus:~# cat /sys/kernel/debug/cdns_pcie_a0*/ltss*
> L0_STATE (0x29)
> L0_STATE (0x29)
> L0_STATE (0x29)
> 
> This implies that the L0_STATE LTSSM state is mapped to 0x29 (41) there,
> which according to your response is internal LTSSM encoding, and hence
> the register read should have resulted in 0x10 instead of 0x29.
> 

Hi Aksh,


For HPA, my view is similar to that of DWC - it requires a common 
internal LTSSM state. For each of its own Root Port drivers, a callback 
can be used to implement the reading of LTSSM. This part can be referred 
to as the implementation of the function in DWC.


static inline enum dw_pcie_ltssm dw_pcie_get_ltssm(struct dw_pcie *pci)
{
	u32 val;

	if (pci->ops && pci->ops->get_ltssm)
		return pci->ops->get_ltssm(pci);

	val = dw_pcie_readl_dbi(pci, PCIE_PORT_DEBUG0);

	return (enum dw_pcie_ltssm)FIELD_GET(PORT_LOGIC_LTSSM_STATE_MASK, val);
}


static int ltssm_status_show(struct seq_file *s, void *v)
{
	struct dw_pcie *pci = s->private;
	enum dw_pcie_ltssm val;

	val = dw_pcie_get_ltssm(pci);
	seq_printf(s, "%s (0x%02x)\n", dw_pcie_ltssm_status_string(val), val);

	return 0;
}



For example, it can be modified as follows. Of course, the function name 
will start with "cdns".

For LGA IP, currently we will allow each Root Port driver to implement 
the corresponding ops::get_ltssm() by itself.

static int ltssm_status_show(struct seq_file *s, void *v)
{
	struct dw_pcie *pci = s->private;
	enum dw_pcie_ltssm val;

	if (pci->ops && pci->ops->get_ltssm)
		val = pci->ops->get_ltssm(pci);
	else
		val = dw_pcie_get_ltssm(pci);
	seq_printf(s, "%s (0x%02x)\n", dw_pcie_ltssm_status_string(val), val);

	return 0;
}


Best regards,
Hans