From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yangbo Lu Subject: [v2, 2/2] mmc: sdhci-of-esdhc: avoid clock glitch when frequency is changing Date: Mon, 26 Dec 2016 17:46:30 +0800 Message-ID: <1482745590-29718-2-git-send-email-yangbo.lu@nxp.com> References: <1482745590-29718-1-git-send-email-yangbo.lu@nxp.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from mail-co1nam03on0051.outbound.protection.outlook.com ([104.47.40.51]:59155 "EHLO NAM03-CO1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755299AbcLZJ7V (ORCPT ); Mon, 26 Dec 2016 04:59:21 -0500 In-Reply-To: <1482745590-29718-1-git-send-email-yangbo.lu@nxp.com> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: linux-mmc@vger.kernel.org, ulf.hansson@linaro.org, Adrian Hunter Cc: Yangbo Lu The eSDHC_PRSSTAT[SDSTB] bit indicates whether the internal card clock is stable. This bit is for the host driver to poll clock status when changing the clock frequency. It is recommended to clear eSDHC_SYSCTL[SDCLKEN] to remove glitch on the card clock when the frequency is changing. This patch is to disable SDCLKEN bit before changing frequency and enable it after SDSTB bit is set. Signed-off-by: Yangbo Lu --- Changes for v2: - added Adrian into to list --- drivers/mmc/host/sdhci-esdhc.h | 5 +++++ drivers/mmc/host/sdhci-of-esdhc.c | 21 ++++++++++++++++++--- 2 files changed, 23 insertions(+), 3 deletions(-) diff --git a/drivers/mmc/host/sdhci-esdhc.h b/drivers/mmc/host/sdhci-esdhc.h index 8cd8449..ece8b37 100644 --- a/drivers/mmc/host/sdhci-esdhc.h +++ b/drivers/mmc/host/sdhci-esdhc.h @@ -31,6 +31,10 @@ * eSDHC register definition */ +/* Present State Register */ +#define ESDHC_PRSSTAT 0x24 +#define ESDHC_CLOCK_STABLE 0x00000008 + /* Protocol Control Register */ #define ESDHC_PROCTL 0x28 #define ESDHC_CTRL_4BITBUS (0x1 << 1) @@ -43,6 +47,7 @@ #define ESDHC_CLOCK_MASK 0x0000fff0 #define ESDHC_PREDIV_SHIFT 8 #define ESDHC_DIVIDER_SHIFT 4 +#define ESDHC_CLOCK_SDCLKEN 0x00000008 #define ESDHC_CLOCK_PEREN 0x00000004 #define ESDHC_CLOCK_HCKEN 0x00000002 #define ESDHC_CLOCK_IPGEN 0x00000001 diff --git a/drivers/mmc/host/sdhci-of-esdhc.c b/drivers/mmc/host/sdhci-of-esdhc.c index 9a6eb44..0849885 100644 --- a/drivers/mmc/host/sdhci-of-esdhc.c +++ b/drivers/mmc/host/sdhci-of-esdhc.c @@ -431,6 +431,7 @@ static void esdhc_of_set_clock(struct sdhci_host *host, unsigned int clock) struct sdhci_esdhc *esdhc = sdhci_pltfm_priv(pltfm_host); int pre_div = 1; int div = 1; + u32 timeout; u32 temp; host->mmc->actual_clock = 0; @@ -451,8 +452,8 @@ static void esdhc_of_set_clock(struct sdhci_host *host, unsigned int clock) } temp = sdhci_readl(host, ESDHC_SYSTEM_CONTROL); - temp &= ~(ESDHC_CLOCK_IPGEN | ESDHC_CLOCK_HCKEN | ESDHC_CLOCK_PEREN - | ESDHC_CLOCK_MASK); + temp &= ~(ESDHC_CLOCK_SDCLKEN | ESDHC_CLOCK_IPGEN | ESDHC_CLOCK_HCKEN | + ESDHC_CLOCK_PEREN | ESDHC_CLOCK_MASK); sdhci_writel(host, temp, ESDHC_SYSTEM_CONTROL); while (host->max_clk / pre_div / 16 > clock && pre_div < 256) @@ -472,7 +473,21 @@ static void esdhc_of_set_clock(struct sdhci_host *host, unsigned int clock) | (div << ESDHC_DIVIDER_SHIFT) | (pre_div << ESDHC_PREDIV_SHIFT)); sdhci_writel(host, temp, ESDHC_SYSTEM_CONTROL); - mdelay(1); + + /* Wait max 20 ms */ + timeout = 20; + while (!(sdhci_readl(host, ESDHC_PRSSTAT) & ESDHC_CLOCK_STABLE)) { + if (timeout == 0) { + pr_err("%s: Internal clock never stabilised.\n", + mmc_hostname(host->mmc)); + return; + } + timeout--; + mdelay(1); + } + + temp |= ESDHC_CLOCK_SDCLKEN; + sdhci_writel(host, temp, ESDHC_SYSTEM_CONTROL); } static void esdhc_pltfm_set_bus_width(struct sdhci_host *host, int width) -- 2.1.0.27.g96db324