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Wed, 18 Dec 2024 12:26:54 +0100 (CET) Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-ap.st.com (STMicroelectronics) with ESMTP id B5B6840048; Wed, 18 Dec 2024 12:25:29 +0100 (CET) Received: from Webmail-eu.st.com (shfdag1node3.st.com [10.75.129.71]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 42FCB26C440; Wed, 18 Dec 2024 12:24:23 +0100 (CET) Received: from [10.129.178.212] (10.129.178.212) by SHFDAG1NODE3.st.com (10.75.129.71) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.37; Wed, 18 Dec 2024 12:24:22 +0100 Message-ID: Date: Wed, 18 Dec 2024 12:24:21 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/5] PCI: stm32: Add PCIe host support for STM32MP25 To: Manivannan Sadhasivam CC: , , , , , , , , , , , , , , , , References: <20241126155119.1574564-1-christian.bruel@foss.st.com> <20241126155119.1574564-3-christian.bruel@foss.st.com> <20241203145244.trgrobtfmumtiwuc@thinkpad> <20241218094606.sljdx2w27thc5ahj@thinkpad> Content-Language: en-US From: Christian Bruel In-Reply-To: <20241218094606.sljdx2w27thc5ahj@thinkpad> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.129.178.212] X-ClientProxiedBy: SHFCAS1NODE2.st.com (10.75.129.73) To SHFDAG1NODE3.st.com (10.75.129.71) X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.60.29 definitions=2024-09-06_09,2024-09-06_01,2024-09-02_01 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241218_032708_042528_73848E6B X-CRM114-Status: GOOD ( 29.69 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 12/18/24 10:46, Manivannan Sadhasivam wrote: > On Mon, Dec 16, 2024 at 10:00:27AM +0100, Christian Bruel wrote: > > [...] > >>> >>>> + msleep(PCIE_T_RRS_READY_MS); >>>> + >>>> + return ret; >>>> +} >>>> + >>>> +static void stm32_pcie_stop_link(struct dw_pcie *pci) >>>> +{ >>>> + struct stm32_pcie *stm32_pcie = to_stm32_pcie(pci); >>>> + >>>> + regmap_update_bits(stm32_pcie->regmap, SYSCFG_PCIECR, >>>> + STM32MP25_PCIECR_LTSSM_EN, 0); >>>> + >>>> + /* Assert PERST# */ >>>> + if (stm32_pcie->perst_gpio) >>>> + gpiod_set_value(stm32_pcie->perst_gpio, 1); >>> >>> I don't like tying PERST# handling with start/stop link. PERST# should be >>> handled based on the power/clock state. >> >> I don't understand your point: We turn off the PHY in suspend_noirq(), so >> that seems a logical place to de-assert in resume_noirq after the refclk is >> ready. PERST# should be kept active until the PHY stablilizes the clock in >> resume. From the PCIe electromechanical specs, PERST# goes active while the >> refclk is not stable/ >> > > While your understanding about PERST# is correct, your implementation is not. > You are toggling PERST# from start/stop link callbacks which are supposed to > control the LTSSM state only. I don't have issues with toggling PERST# in > stm32_pcie_{suspend/resume}_noirq(). Ah OK. this function is split now into 2 functional blocks in the upcoming version > >> >>> >>>> +} >>>> + >>>> +static int stm32_pcie_suspend(struct device *dev) >>>> +{ >>>> + struct stm32_pcie *stm32_pcie = dev_get_drvdata(dev); >>>> + >>>> + if (device_may_wakeup(dev) || device_wakeup_path(dev)) >>>> + enable_irq_wake(stm32_pcie->wake_irq); >>>> + >>>> + return 0; >>>> +} >>>> + >>>> +static int stm32_pcie_resume(struct device *dev) >>>> +{ >>>> + struct stm32_pcie *stm32_pcie = dev_get_drvdata(dev); >>>> + >>>> + if (device_may_wakeup(dev) || device_wakeup_path(dev)) >>>> + disable_irq_wake(stm32_pcie->wake_irq); >>>> + >>>> + return 0; >>>> +} >>>> + >>>> +static int stm32_pcie_suspend_noirq(struct device *dev) >>>> +{ >>>> + struct stm32_pcie *stm32_pcie = dev_get_drvdata(dev); >>>> + >>>> + stm32_pcie->link_is_up = dw_pcie_link_up(stm32_pcie->pci); >>>> + >>>> + stm32_pcie_stop_link(stm32_pcie->pci); >>> >>> I don't understand how endpoint can wakeup the host if PERST# gets asserted. >> >> The stm32 PCIe doesn't support L2, we don't expect an in-band beacon for the >> wakeup. We support wakeup only from sideband WAKE#, that will restart the >> link from IRQ >> > > I don't understand how WAKE# is supported without L2. Only in L2 state, endpoint > will make use of Vaux and it will wakeup the host using either beacon or WAKE#. > If you don't support L2, then the endpoint will reach L3 (link off) state. I think this is what happens, my understanding is that the device is still powered to get the wakeup event (eg WoL magic packet), triggers the PCIe wake_IRQ from the WAKE#. > >>> >>>> + clk_disable_unprepare(stm32_pcie->clk); >>>> + >>>> + if (!device_may_wakeup(dev) && !device_wakeup_path(dev)) >>>> + phy_exit(stm32_pcie->phy); >>>> + >>>> + return pinctrl_pm_select_sleep_state(dev); >>>> +} >>>> + >>>> +static int stm32_pcie_resume_noirq(struct device *dev) >>>> +{ >>>> + struct stm32_pcie *stm32_pcie = dev_get_drvdata(dev); >>>> + struct dw_pcie *pci = stm32_pcie->pci; >>>> + struct dw_pcie_rp *pp = &pci->pp; >>>> + int ret; >>>> + >>>> + /* init_state must be called first to force clk_req# gpio when no >>> >>> CLKREQ# >>> >>> Why RC should control CLKREQ#? >> >> REFCLK is gated with CLKREQ#, So we cannot access the core >> without CLKREQ# if no device is present. So force it with a init pinmux >> the time to init the PHY and the core DBI registers >> > > Ok. You should add a comment to clarify it in the code as this is not a standard > behavior. > OK >>> >>> Also please use preferred style for multi-line comments: >>> >>> /* >>> * ... >>> */ >>> >>>> + * device is plugged. >>>> + */ >>>> + if (!IS_ERR(dev->pins->init_state)) >>>> + ret = pinctrl_select_state(dev->pins->p, dev->pins->init_state); >>>> + else >>>> + ret = pinctrl_pm_select_default_state(dev); >>>> + >>>> + if (ret) { >>>> + dev_err(dev, "Failed to activate pinctrl pm state: %d\n", ret); >>>> + return ret; >>>> + } >>>> + >>>> + if (!device_may_wakeup(dev) && !device_wakeup_path(dev)) { >>>> + ret = phy_init(stm32_pcie->phy); >>>> + if (ret) { >>>> + pinctrl_pm_select_default_state(dev); >>>> + return ret; >>>> + } >>>> + } >>>> + >>>> + ret = clk_prepare_enable(stm32_pcie->clk); >>>> + if (ret) >>>> + goto clk_err; >>> >>> Please name the goto labels of their purpose. Like err_phy_exit. >> >> OK >> >>> >>>> + >>>> + ret = dw_pcie_setup_rc(pp); >>>> + if (ret) >>>> + goto pcie_err; >>> >>> This should be, 'err_disable_clk'. >>> >>>> + >>>> + if (stm32_pcie->link_is_up) { >>> >>> Why do you need this check? You cannot start the link in the absence of an >>> endpoint? >>> >> >> It is an optimization to avoid unnecessary "dw_pcie_wait_for_link" if no >> device is present during suspend >> > > In that case you'll not trigger LTSSM if there was no endpoint connected before > suspend. What if users connect an endpoint after resume? Yes, exactly. We don't support hotplug, and plugging a device while the system is in stand-by is something that we don't expect. The imx6 platform does this also. thanks, Christian > > - Mani >