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b=UokOtzCUttYGgkGIh2r2zAIvnm2J+Sro2TMwLdN8/3aVguTADhucdaUevznrK9FgXDAeJ1KlodkefCHJz2r8qX74U58fT4fxUoUgqKps1REvC5yW8X8CcchRrGtIWdoZrq0lhAlv9tYAarJ+CtLn3lyvvaXhYYlUqpbwxIKInbzBIxj2so3RPrWSWF3f4/Bd1LhiSBoVicsxI/WbDa2JLGdtbNtF5EZYAOwV3C6zNlb4HKpY3vTokxjJRsaalJVVTR87c1eNPwv2ivbbnu6l4fF9QYzljWTfZtKy2pWcvo0fz5NJgvRFX2gWi4ej5H1zo2Tim+mNXyhKcM9gIE9iNA== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from DS0PR12MB8245.namprd12.prod.outlook.com (2603:10b6:8:f2::16) by CY8PR12MB7683.namprd12.prod.outlook.com (2603:10b6:930:86::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9723.7; Sun, 15 Mar 2026 17:16:18 +0000 Received: from DS0PR12MB8245.namprd12.prod.outlook.com ([fe80::e7c5:cfca:a597:7fa4]) by DS0PR12MB8245.namprd12.prod.outlook.com ([fe80::e7c5:cfca:a597:7fa4%4]) with mapi id 15.20.9723.014; Sun, 15 Mar 2026 17:16:18 +0000 Message-ID: <2ec931b6-a287-419e-821e-35420c12378d@nvidia.com> Date: Sun, 15 Mar 2026 22:46:08 +0530 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 1/9] PCI: tegra194: Drive CLKREQ# signal low explicitly To: Manivannan Sadhasivam Cc: "bhelgaas@google.com" , "lpieralisi@kernel.org" , "kwilczynski@kernel.org" , "robh@kernel.org" , "krzk+dt@kernel.org" , "conor+dt@kernel.org" , "thierry.reding@gmail.com" , Jon Hunter , "kishon@kernel.org" , "arnd@arndb.de" , "gregkh@linuxfoundation.org" , "Frank.Li@nxp.com" , "den@valinux.co.jp" , "hongxing.zhu@nxp.com" , "jingoohan1@gmail.com" , Vidya Sagar , "cassel@kernel.org" , "18255117159@163.com" <18255117159@163.com>, "linux-pci@vger.kernel.org" , "linux-tegra@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <20260303065758.2364340-1-mmaddireddy@nvidia.com> <20260303065758.2364340-2-mmaddireddy@nvidia.com> Content-Language: en-US From: Manikanta Maddireddy X-Nvconfidentiality: public In-Reply-To: Content-Type: text/plain; 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So, as a workaround, this >> patch drives the CLKREQ# of the Root Port itself low to avoid link up >> issues between PCIe switch downstream port and Endpoint devices. This is > > Is the CLKREQ# signal shared with the switch and the endpoint devices > connected to its downstream port also? > Yes, this is the observation. >> not a wrong thing to do after all the CLKREQ# is anyway being overridden >> to '0' internally and now it is just that the same is being propagated >> outside also. >> > > What do you mean by 'propagating outside'? > > And what is the difference between APPL_PINMUX_CLKREQ_OVERRIDE and > APPL_PINMUX_CLKREQ_DEFAULT_VALUE? > > - Mani APPL_PINMUX_CLKREQ_OVERRIDE: This overrides CLKREQ# input PAD to PCIe controller. APPL_PINMUX_CLKREQ_OVERRIDE: This overrides CLKREQ# output PAD to low. Propagating outside means driving CLKREQ# pin as low. - Manikanta > >> Reviewed-by: Jon Hunter >> Tested-by: Jon Hunter >> Signed-off-by: Vidya Sagar >> Signed-off-by: Manikanta Maddireddy >> --- >> Changes V6 -> V7: Fix commit message >> Changes V1 -> V6: None >> >> drivers/pci/controller/dwc/pcie-tegra194.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c >> index b1ae46761915..2f1f882fc737 100644 >> --- a/drivers/pci/controller/dwc/pcie-tegra194.c >> +++ b/drivers/pci/controller/dwc/pcie-tegra194.c >> @@ -44,6 +44,7 @@ >> #define APPL_PINMUX_CLKREQ_OVERRIDE BIT(3) >> #define APPL_PINMUX_CLK_OUTPUT_IN_OVERRIDE_EN BIT(4) >> #define APPL_PINMUX_CLK_OUTPUT_IN_OVERRIDE BIT(5) >> +#define APPL_PINMUX_CLKREQ_DEFAULT_VALUE BIT(13) >> >> #define APPL_CTRL 0x4 >> #define APPL_CTRL_SYS_PRE_DET_STATE BIT(6) >> @@ -1411,6 +1412,7 @@ static int tegra_pcie_config_controller(struct tegra_pcie_dw *pcie, >> val = appl_readl(pcie, APPL_PINMUX); >> val |= APPL_PINMUX_CLKREQ_OVERRIDE_EN; >> val &= ~APPL_PINMUX_CLKREQ_OVERRIDE; >> + val &= ~APPL_PINMUX_CLKREQ_DEFAULT_VALUE; >> appl_writel(pcie, val, APPL_PINMUX); >> } >> >> -- >> 2.34.1 >> > -- nvpublic