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Fri, 11 Sep 2026 14:16:08 -0700 (PDT) From: =?UTF-8?q?Enrique=20Hern=C3=A1ndez=20Bello?= To: shawn.lin@rock-chips.com, lpieralisi@kernel.org, kwilczynski@kernel.org, mani@kernel.org, bhelgaas@google.com Cc: robh@kernel.org, heiko@sntech.de, dlemoal@kernel.org, linux-pci@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, =?UTF-8?q?Enrique=20Hern=C3=A1ndez=20Bello?= Subject: [PATCH v2] PCI: rockchip: Skip the Tpvperl wait when power is already valid Date: Fri, 11 Sep 2026 22:15:59 +0100 Message-ID: <20260911211559.207990-1-ehbello@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Since commit c47f90be4c89 ("PCI: rockchip-host: Fix rockchip_pcie_host_init_port() PERST# handling"), a JMicron JMB585 behind an rk3399 root port almost never becomes usable: the link trains normally, but the endpoint's configuration space never answers, so the device is not enumerated. On this controller a configuration read that gets no usable completion is reported as an external abort rather than as an all-ones response, which on arm64 brings the machine down. The change added an unconditional 100 ms sleep so that PERST# stays asserted for at least Tpvperl after power becomes valid. The wait is performed while PERST# is asserted, so it also extends the reset by 100 ms, and this endpoint does not tolerate the longer assertion. Tpvperl is counted from the supplies becoming valid (PCIe CEM r5.1, sec 2.9.2). On boards whose PCIe supplies are always-on -- vcc3v3_pcie on ROCK Pi 4 is regulator-always-on and regulator-boot-on -- power has been valid since boot, seconds before the driver probes, so the requirement is already met and the sleep only lengthens the reset. Record whether the supplies were already enabled before the driver enabled them, and skip the wait in that case. A supply that is already on at probe was brought up either by the bootloader or by the regulator core at boot, both of which precede a PCIe probe by far more than Tpvperl. When the driver really does bring the rails up the full wait still happens, as it does if regulator_is_enabled() cannot tell. The same check is repeated on resume rather than assuming that power was cycled: suspend calls regulator_disable() on the 0.9V supply, which only drops a reference, so on a board where that rail is always-on or shared with another consumer the power stays valid across the cycle. Skipping the wait only when every supply is already on is strictly more conservative than what this driver did for years: until the change cited above there was no Tpvperl wait at all, and PERST# stayed asserted only for as long as the register writes in between took. Measured on a ROCK Pi 4C with a Radxa Penta SATA HAT (JMB585) by booting repeatedly and counting how often the endpoint enumerated: unmodified .................................... 0 out of 84 boots with this patch ............................... 3 out of 3 boots other ways of dropping the same wait .......... 16 out of 16 boots Fisher's exact test, pooling the last two rows against the first, gives p = 4.1e-21. With the patch the endpoint enumerated on every boot and all four disks behind it came up. Each of the three PERST#-related changes that landed together in v6.11-rc1 was also reverted individually; only removing this wait made any difference. Moving the wait to before link training is enabled, rather than removing it, did not help (0 out of 15 boots), which is what identified the length of the PERST# assertion rather than any interaction with link training as the cause. The measurements were taken on 6.18, but the code in question is unchanged between v6.11 and v7.2. Fixes: c47f90be4c89 ("PCI: rockchip-host: Fix rockchip_pcie_host_init_port() PERST# handling") Cc: stable@vger.kernel.org Signed-off-by: Enrique Hernández Bello --- --- v2: - Re-evaluate the supplies in rockchip_pcie_resume_noirq() instead of assuming that the 0.9V rail was really turned off. On a board where that rail is always-on or shared, regulator_disable() leaves it on, and forcing the wait there would reintroduce on resume exactly the failure this patch fixes. Spotted by an automated review of v1. - Factor the test into rockchip_pcie_supplies_enabled() now that it has two callers. v1: https://lore.kernel.org/all/20260911104952.4190994-1-ehbello@gmail.com/ --- a/drivers/pci/controller/pcie-rockchip.h +++ b/drivers/pci/controller/pcie-rockchip.h @@ -318,6 +318,7 @@ struct regulator *vpcie1v8; /* 1.8V power supply */ struct regulator *vpcie0v9; /* 0.9V power supply */ struct gpio_desc *perst_gpio; + bool supplies_pre_enabled; u32 lanes; u8 lanes_map; int link_gen; --- a/drivers/pci/controller/pcie-rockchip-host.c +++ b/drivers/pci/controller/pcie-rockchip-host.c @@ -314,7 +314,9 @@ rockchip_pcie_write(rockchip, PCIE_CLIENT_LINK_TRAIN_ENABLE, PCIE_CLIENT_CONFIG); - msleep(PCIE_T_PVPERL_MS); + if (!rockchip->supplies_pre_enabled) + msleep(PCIE_T_PVPERL_MS); + gpiod_set_value_cansleep(rockchip->perst_gpio, 1); msleep(PCIE_RESET_CONFIG_WAIT_MS); @@ -609,11 +611,33 @@ return 0; } +/* + * Tpvperl is counted from the supplies becoming valid, and the driver waits + * for it with PERST# asserted, so the wait also lengthens the reset pulse. + * Supplies that are already enabled before this driver enables them were + * brought up by the bootloader or by the regulator core at boot, both of + * which precede this point by far more than Tpvperl, so the requirement is + * already met. Treat an error from regulator_is_enabled() as "not known to + * be on" so that the caller waits. + */ +static bool rockchip_pcie_supplies_enabled(struct rockchip_pcie *rockchip) +{ + return (IS_ERR(rockchip->vpcie12v) || + regulator_is_enabled(rockchip->vpcie12v) > 0) && + (IS_ERR(rockchip->vpcie3v3) || + regulator_is_enabled(rockchip->vpcie3v3) > 0) && + regulator_is_enabled(rockchip->vpcie1v8) > 0 && + regulator_is_enabled(rockchip->vpcie0v9) > 0; +} + static int rockchip_pcie_set_vpcie(struct rockchip_pcie *rockchip) { struct device *dev = rockchip->dev; int err; + rockchip->supplies_pre_enabled = + rockchip_pcie_supplies_enabled(rockchip); + if (!IS_ERR(rockchip->vpcie12v)) { err = regulator_enable(rockchip->vpcie12v); if (err) { @@ -890,6 +914,13 @@ struct rockchip_pcie *rockchip = dev_get_drvdata(dev); int err; + /* + * Suspend calls regulator_disable() on the 0.9V supply, but on boards + * where it is always-on or shared the rail does not actually drop, so + * re-evaluate instead of assuming that power was cycled. + */ + rockchip->supplies_pre_enabled = rockchip_pcie_supplies_enabled(rockchip); + err = regulator_enable(rockchip->vpcie0v9); if (err) { dev_err(dev, "fail to enable vpcie0v9 regulator\n");