linux-kernel - Re: [PATCH v4 5/7] PCI: spacemit: introduce SpacemiT PCIe host driver

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Message-ID: <6872beb1-f27f-48b9-a756-5b7faa380cec@riscstar.com>
Date: Mon, 3 Nov 2025 10:51:11 -0600
From: Alex Elder <elder@...cstar.com>
To: lpieralisi@...nel.org, kwilczynski@...nel.org, mani@...nel.org,
 robh@...nel.org, bhelgaas@...gle.com, dlan@...too.org, johannes@...felt.com,
 p.zabel@...gutronix.de, christian.bruel@...s.st.com,
 thippeswamy.havalige@....com, krishna.chundru@....qualcomm.com,
 mayank.rana@....qualcomm.com, qiang.yu@....qualcomm.com,
 shradha.t@...sung.com, inochiama@...il.com, guodong@...cstar.com,
 linux-pci@...r.kernel.org, spacemit@...ts.linux.dev,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 5/7] PCI: spacemit: introduce SpacemiT PCIe host driver

On 10/31/25 5:31 PM, Aurelien Jarno wrote:
> Hi Alex,
> 
> On 2025-10-30 17:02, Alex Elder wrote:
>> +/* Disable ASPM L1 for now, until reported errors can be reproduced */
> 
> Thanks for adding this function.
> 
>> +static void k1_pcie_post_init(struct dw_pcie_rp *pp)
>> +{
>> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
>> +	u8 offset;
>> +	u32 val;
>> +
>> +	offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
>> +
>> +	dw_pcie_dbi_ro_wr_en(pci);
>> +
>> +	/* Turn off ASPM L1 for the link */
>> +	val = readl(pci->dbi_base + offset + PCI_EXP_LNKCAP);
> 
> Why not using dw_pcie_readl_dbi() instead?
> 
>> +	val &= ~PCI_EXP_LNKCAP_ASPM_L1;
>> +	writel(val, pci->dbi_base + offset + PCI_EXP_LNKCAP);
> 
> And here dw_pcie_writel_dbi()?
> 
>> +
>> +	dw_pcie_dbi_ro_wr_dis(pci);
>> +}
>> +
>> +static void k1_pcie_deinit(struct dw_pcie_rp *pp)
>> +{
>> +	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
>> +	struct k1_pcie *k1 = to_k1_pcie(pci);
>> +
>> +	/* Assert fundamental reset (drive PERST# low) */
>> +	regmap_set_bits(k1->pmu, k1->pmu_off + PCIE_CLK_RESET_CONTROL,
>> +			PCIE_RC_PERST);
>> +
>> +	phy_exit(k1->phy);
>> +
>> +	k1_pcie_disable_resources(k1);
>> +}
>> +
>> +static const struct dw_pcie_host_ops k1_pcie_host_ops = {
>> +	.init		= k1_pcie_init,
>> +	.post_init	= k1_pcie_post_init,
> 
> Unfortunately, while I can see the effect of the change with for
> instance lspci -vvv, this happens way too late in the device scan
> process, i.e. after pcie_aspm_override_default_link_state() and causes
> L1 to still be enabled.

OK thanks for this information.  I am going to contact you
privately to get more information on your errors (and those
Johannes is reporting) so that I can try to resolve them
before I post the next version of this patch series.

					-Alex

> 
> I have tried to move it earlier, in k1_pcie_init() after writing the
> vendor and device IDs. This works as long as "nvme scan" is run in
> U-Boot. But if I don't run this command, it seems that the change is
> ignored or lost (i.e. I can still see L1 enabled with lspci -vvv).
> 
> Moving it at the end of k1_pcie_init() works fine, like moving it at the
> beginning of k1_pcie_start_link(). But my knowledge is too limited to
> know where is the correct place.
> 
> Regards
> Aurelien
>