linux-kernel - [PATCH V3 15/21] PCI: tegra194: Disable L1.2 capability of Tegra234 EP

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Date:   Fri, 14 Oct 2022 00:08:48 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     <lpieralisi@...nel.org>, <robh@...nel.org>, <kw@...ux.com>,
        <bhelgaas@...gle.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <kishon@...com>, <vkoul@...nel.org>,
        <mani@...nel.org>, <Sergey.Semin@...kalelectronics.ru>,
        <ffclaire1224@...il.com>
CC:     <linux-pci@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-phy@...ts.infradead.org>,
        <kthota@...dia.com>, <mmaddireddy@...dia.com>, <vidyas@...dia.com>,
        <sagar.tv@...il.com>
Subject: [PATCH V3 15/21] PCI: tegra194: Disable L1.2 capability of Tegra234 EP

When Tegra234 is operating in the endpoint mode with L1.2 enabled, PCIe
link goes down during L1.2 exit. This is because Tegra234 is powering up
UPHY PLL immediately without making sure that the REFCLK is stable.
This is causing UPHY PLL to not lock to the correct frequency and leading
to link going down. There is no hardware fix for this, hence do not
advertise the L1.2 capability in the endpoint mode.

Signed-off-by: Vidya Sagar <vidyas@...dia.com>
---
V3:
* This is a new patch in this series

 drivers/pci/controller/dwc/pcie-tegra194.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
index e6fd713e9868..d592cf68b02c 100644
--- a/drivers/pci/controller/dwc/pcie-tegra194.c
+++ b/drivers/pci/controller/dwc/pcie-tegra194.c
@@ -246,6 +246,7 @@ struct tegra_pcie_dw_of_data {
 	bool has_sbr_reset_fix;
 	bool has_l1ss_exit_fix;
 	bool has_ltr_req_fix;
+	bool disable_l1_2;
 	u32 cdm_chk_int_en_bit;
 	u32 gen4_preset_vec;
 	u8 n_fts[2];
@@ -1967,10 +1968,11 @@ static void pex_ep_event_pex_rst_deassert(struct tegra_pcie_dw *pcie)
 	init_host_aspm(pcie);
 
 	/* Disable ASPM-L1SS advertisement if there is no CLKREQ routing */
-	if (!pcie->supports_clkreq) {
+	if (!pcie->supports_clkreq)
 		disable_aspm_l11(pcie);
+
+	if (!pcie->supports_clkreq || pcie->of_data->disable_l1_2)
 		disable_aspm_l12(pcie);
-	}
 
 	if (!pcie->of_data->has_l1ss_exit_fix) {
 		val = dw_pcie_readl_dbi(pci, GEN3_RELATED_OFF);
@@ -2589,6 +2591,7 @@ static const struct tegra_pcie_dw_of_data tegra234_pcie_dw_ep_of_data = {
 	.mode = DW_PCIE_EP_TYPE,
 	.has_l1ss_exit_fix = true,
 	.has_ltr_req_fix = true,
+	.disable_l1_2 = true,
 	.cdm_chk_int_en_bit = BIT(18),
 	/* Gen4 - 6, 8 and 9 presets enabled */
 	.gen4_preset_vec = 0x340,
-- 
2.17.1