From: Francesco Dolcini <francesco.dolcini@toradex.com>
To: Lucas Stach <l.stach@pengutronix.de>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: "Richard Zhu" <hongxing.zhu@nxp.com>,
"Rob Herring" <robh@kernel.org>,
"Krzysztof Wilczyński" <kw@linux.com>,
"Pengutronix Kernel Team" <kernel@pengutronix.de>,
"Fabio Estevam" <festevam@gmail.com>,
"NXP Linux Team" <linux-imx@nxp.com>,
"Bjorn Helgaas" <helgaas@kernel.org>,
"Shawn Guo" <shawnguo@kernel.org>,
"Sascha Hauer" <s.hauer@pengutronix.de>,
linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
"Francesco Dolcini" <francesco.dolcini@toradex.com>
Subject: Re: [PATCH v2] PCI: imx6: Fix PERST# start-up sequence
Date: Thu, 3 Mar 2022 08:34:57 +0100 [thread overview]
Message-ID: <20220303073457.GA333450@francesco-nb.int.toradex.com> (raw)
In-Reply-To: <20220214161522.102810-1-francesco.dolcini@toradex.com>
Just a gently ping. Should I resend adding the acked-by Richard Zhu?
Francesco
On Mon, Feb 14, 2022 at 05:15:22PM +0100, Francesco Dolcini wrote:
> According to the PCIe standard the PERST# signal (reset-gpio in
> fsl,imx* compatible dts) should be kept asserted for at least 100 usec
> before the PCIe refclock is stable, should be kept asserted for at
> least 100 msec after the power rails are stable and the host should wait
> at least 100 msec after it is de-asserted before accessing the
> configuration space of any attached device.
>
> From PCIe CEM r2.0, sec 2.6.2
>
> T-PVPERL: Power stable to PERST# inactive - 100 msec
> T-PERST-CLK: REFCLK stable before PERST# inactive - 100 usec.
>
> From PCIe r5.0, sec 6.6.1
>
> With a Downstream Port that does not support Link speeds greater than
> 5.0 GT/s, software must wait a minimum of 100 ms before sending a
> Configuration Request to the device immediately below that Port.
>
> Failure to do so could prevent PCIe devices to be working correctly,
> and this was experienced with real devices.
>
> Move reset assert to imx6_pcie_assert_core_reset(), this way we ensure
> that PERST# is asserted before enabling any clock, move de-assert to the
> end of imx6_pcie_deassert_core_reset() after the clock is enabled and
> deemed stable and add a new delay of 100 msec just afterward.
>
> Link: https://lore.kernel.org/all/20220211152550.286821-1-francesco.dolcini@toradex.com
> Fixes: bb38919ec56e ("PCI: imx6: Add support for i.MX6 PCIe controller")
> Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
> ---
> v2: Add complete reference to the PCIe standards, s/PCI-E/PCIe/g
> ---
> drivers/pci/controller/dwc/pci-imx6.c | 23 ++++++++++++++---------
> 1 file changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 7b200b66114a..73baa2044ccf 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -408,6 +408,11 @@ static void imx6_pcie_assert_core_reset(struct imx6_pcie *imx6_pcie)
> dev_err(dev, "failed to disable vpcie regulator: %d\n",
> ret);
> }
> +
> + /* Some boards don't have PCIe reset GPIO. */
> + if (gpio_is_valid(imx6_pcie->reset_gpio))
> + gpio_set_value_cansleep(imx6_pcie->reset_gpio,
> + imx6_pcie->gpio_active_high);
> }
>
> static unsigned int imx6_pcie_grp_offset(const struct imx6_pcie *imx6_pcie)
> @@ -544,15 +549,6 @@ static void imx6_pcie_deassert_core_reset(struct imx6_pcie *imx6_pcie)
> /* allow the clocks to stabilize */
> usleep_range(200, 500);
>
> - /* Some boards don't have PCIe reset GPIO. */
> - if (gpio_is_valid(imx6_pcie->reset_gpio)) {
> - gpio_set_value_cansleep(imx6_pcie->reset_gpio,
> - imx6_pcie->gpio_active_high);
> - msleep(100);
> - gpio_set_value_cansleep(imx6_pcie->reset_gpio,
> - !imx6_pcie->gpio_active_high);
> - }
> -
> switch (imx6_pcie->drvdata->variant) {
> case IMX8MQ:
> reset_control_deassert(imx6_pcie->pciephy_reset);
> @@ -599,6 +595,15 @@ static void imx6_pcie_deassert_core_reset(struct imx6_pcie *imx6_pcie)
> break;
> }
>
> + /* Some boards don't have PCIe reset GPIO. */
> + if (gpio_is_valid(imx6_pcie->reset_gpio)) {
> + msleep(100);
> + gpio_set_value_cansleep(imx6_pcie->reset_gpio,
> + !imx6_pcie->gpio_active_high);
> + /* Wait for 100ms after PERST# deassertion (PCIe r5.0, 6.6.1) */
> + msleep(100);
> + }
> +
> return;
>
> err_ref_clk:
> --
> 2.25.1
>
prev parent reply other threads:[~2022-03-03 7:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-14 16:15 [PATCH v2] PCI: imx6: Fix PERST# start-up sequence Francesco Dolcini
2022-02-16 8:24 ` Hongxing Zhu
2022-03-03 7:34 ` Francesco Dolcini [this message]
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