From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751068AbeBHFTU (ORCPT ); Thu, 8 Feb 2018 00:19:20 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:37148 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750711AbeBHFTR (ORCPT ); Thu, 8 Feb 2018 00:19:17 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 9697460790 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=vviswana@codeaurora.org From: Vijay Viswanath Subject: Re: [PATCH RFC 2/2] mmc: sdhci-msm: support voltage pad switching To: Bjorn Andersson Cc: adrian.hunter@intel.com, ulf.hansson@linaro.org, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, shawn.lin@rock-chips.com, linux-arm-msm@vger.kernel.org, georgi.djakov@linaro.org, asutoshd@codeaurora.org, stummala@codeaurora.org, venkatg@codeaurora.org, pramod.gurav@linaro.org, jeremymc@redhat.com, Krishna Konda References: <1516262742-44326-1-git-send-email-vviswana@codeaurora.org> <1516262742-44326-3-git-send-email-vviswana@codeaurora.org> <20180202215154.GI12728@builder> Message-ID: <288d817a-0c9d-5c9f-c0bc-c5b523793670@codeaurora.org> Date: Thu, 8 Feb 2018 10:49:10 +0530 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180202215154.GI12728@builder> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/3/2018 3:21 AM, Bjorn Andersson wrote: > On Thu 18 Jan 00:05 PST 2018, Vijay Viswanath wrote: > >> From: Krishna Konda >> >> The PADs for sdhc controller are dual-voltage that support 3v/1.8v. >> Those PADs have a control signal (io_pad_pwr_switch/mode18 ) that >> indicates whether the PAD works in 3v or 1.8v. >> >> SDHC core on msm platforms should have IO_PAD_PWR_SWITCH bit set/unset >> based on actual voltage used for IO lines. So when power irq is >> triggered for io high or io low, the driver should check the voltages >> supported and set the pad accordingly. >> > > I'll try to find some time to check that this doesn't break 8916 and > 8974...again... > Thanks! Btwn, I had tested the code in db410c. >> Signed-off-by: Krishna Konda >> Signed-off-by: Venkat Gopalakrishnan >> Signed-off-by: Vijay Viswanath >> --- >> drivers/mmc/host/sdhci-msm.c | 38 ++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 38 insertions(+) >> >> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c >> index 5c23e92..f5728a8 100644 >> --- a/drivers/mmc/host/sdhci-msm.c >> +++ b/drivers/mmc/host/sdhci-msm.c >> @@ -78,6 +78,8 @@ >> #define CORE_HC_MCLK_SEL_DFLT (2 << 8) >> #define CORE_HC_MCLK_SEL_HS400 (3 << 8) >> #define CORE_HC_MCLK_SEL_MASK (3 << 8) >> +#define CORE_IO_PAD_PWR_SWITCH_EN (1 << 15) >> +#define CORE_IO_PAD_PWR_SWITCH (1 << 16) >> #define CORE_HC_SELECT_IN_EN BIT(18) >> #define CORE_HC_SELECT_IN_HS400 (6 << 19) >> #define CORE_HC_SELECT_IN_MASK (7 << 19) >> @@ -1166,6 +1168,35 @@ static void sdhci_msm_handle_pwr_irq(struct sdhci_host *host, int irq) >> */ >> writel_relaxed(irq_ack, msm_host->core_mem + CORE_PWRCTL_CTL); >> >> + /* >> + * SDHC has core_mem and hc_mem device memory and these memory >> + * addresses do not fall within 1KB region. Hence, any update to >> + * core_mem address space would require an mb() to ensure this gets >> + * completed before its next update to registers within hc_mem. >> + */ >> + mb(); > > If you just use writel() instead of writel_relaxed() you don't need to > sprinkle the driver with comments like this. And you really should be > able to just say "Ensure ordering between core_mem and hc_mem writes" if > you really feel like making it explicit. > >> + /* >> + * We should unset IO PAD PWR switch only if the register write can >> + * set IO lines high and the regulator also switches to 3 V. >> + * Else, we should keep the IO PAD PWR switch set. >> + * This is applicable to certain targets where eMMC vccq supply is only >> + * 1.8V. In such targets, even during REQ_IO_HIGH, the IO PAD PWR >> + * switch must be kept set to reflect actual regulator voltage. This >> + * way, during initialization of controllers with only 1.8V, we will >> + * set the IO PAD bit without waiting for a REQ_IO_LOW. >> + */ >> + if ((io_level & REQ_IO_HIGH) && (msm_host->caps_0 & CORE_3_0V_SUPPORT)) >> + writel_relaxed((readl_relaxed(host->ioaddr + CORE_VENDOR_SPEC) & >> + ~CORE_IO_PAD_PWR_SWITCH), host->ioaddr + >> + CORE_VENDOR_SPEC); > > Please split this up in read, modify and write operations. > Will do >> + else if ((io_level & REQ_IO_LOW) || >> + (msm_host->caps_0 & CORE_1_8V_SUPPORT)) >> + writel_relaxed((readl_relaxed(host->ioaddr + CORE_VENDOR_SPEC) | >> + CORE_IO_PAD_PWR_SWITCH), host->ioaddr + >> + CORE_VENDOR_SPEC); >> + /* Ensure that the IO PAD switches are updated before proceeding */ > > That's not what "mb()" does, it ensures that any writes that was done > before this line will hit the hardware before any writes that is done > after this line. > Will update the comments. > But again, using writel() would save us from doing this explicitly > throughout the code. > >> + mb(); >> + >> if (pwr_state) >> msm_host->curr_pwr_state = pwr_state; >> if (io_level) >> @@ -1518,6 +1549,13 @@ static int sdhci_msm_probe(struct platform_device *pdev) >> } >> >> /* >> + * Set the PAD_PWR_SWITCH_EN bit so that the PAD_PWR_SWITCH bit can >> + * be used as required later on. >> + */ >> + writel_relaxed((readl_relaxed(host->ioaddr + CORE_VENDOR_SPEC) | >> + CORE_IO_PAD_PWR_SWITCH_EN), host->ioaddr + >> + CORE_VENDOR_SPEC); > > Please rewrite as 3 operations. > > Do we need to set the pwr switch value as well? Or we're fine relying on > the existing value here? After the IO_PAD_PWR_SWTCH is enabled, we will call sdhci_msm_handle_pwr_irq. If there is any pending power irq interrupt, that will set the appropriate pwr switch value. Otherwise, an appropriate value will get set during REQ_BUS_ON event. > > Regards, > Bjorn > -- > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >