[PATCH 2/4] PCI: tegra194: Remove unnecessary L1SS disable code

[Niklas Cassel]

On Tue, Nov 18, 2025 at 12:59:17PM -0600, Bjorn Helgaas wrote:
> On Wed, Nov 12, 2025 at 09:29:20AM +0100, Niklas Cassel wrote:
> > On Tue, Nov 11, 2025 at 04:16:09PM -0600, Bjorn Helgaas wrote:
> > > From: Bjorn Helgaas <bhelgaas at google.com>
> > >
> > > The DWC core clears the L1 Substates Supported bits unless the driver sets
> > > the "dw_pcie.l1ss_support" flag.
> > >
> > > The tegra194 init_host_aspm() sets "dw_pcie.l1ss_support" if the platform
> > > has the "supports-clkreq" DT property.  If "supports-clkreq" is absent,
> > > "dw_pcie.l1ss_support" is not set, and the DWC core will clear the L1
> > > Substates Supported bits.
> > >
> > > The tegra194 code to clear the L1 Substates Supported bits is unnecessary,
> > > so remove it.
> > >
> > > Signed-off-by: Bjorn Helgaas <bhelgaas at google.com>
> > > ---
> >
> > Since init_host_aspm() is now the only place using struct tegra_pcie_dw
> > struct member cfg_link_cap_l1sub, I think that you can remove this struct
> > member, and instead make this a local variable in init_host_aspm().
>
> It looks like tegra_pcie_ep_irq_thread() also uses it, although I'm
> dubious about that.
>
> It's odd that software would be responsible for sending LTR messages,
> but I guess this only happens for tegra194_pcie_dw_ep_of_data, and
> apparently it's fixed (".has_ltr_req_fix" for tegra234.
>
> And odd that we would read the capability register on every interrupt
> even though this driver is the only thing that can change it, so we
> should be able to cache the value in init_host_aspm().

Yes, sorry, my thinking was that this code in tegra_pcie_ep_irq_thread():

	/* If EP doesn't advertise L1SS, just return */
	val = dw_pcie_readl_dbi(pci, pcie->cfg_link_cap_l1sub);
	if (!(val & (PCI_L1SS_CAP_ASPM_L1_1 | PCI_L1SS_CAP_ASPM_L1_2)))
		return IRQ_HANDLED;


after your patch can be replaced with:

	/* If EP doesn't advertise L1SS, just return */
	if (!pci->l1ss_support)
		return IRQ_HANDLED;


Since we already know that if !pci->l1ss_support,
these bits will be cleared by DWC common code.


So, after that, we could replace the struct tegra_pcie_dw
struct member cfg_link_cap_l1sub with a local variable in
init_host_aspm().


Kind regards,
Niklas