linux-kernel - [RFC] mmc: sdhci: implement light and heavy runtime pm resume

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Message-ID: <20150205182031.1a47d726@xhacker>
Date:	Thu, 5 Feb 2015 18:20:31 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	Ulf Hansson <ulf.hansson@...aro.org>,
	Chris Ball <chris@...ntf.net>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: [RFC] mmc: sdhci: implement light and heavy runtime pm resume

Hi all,

Most sdhci_runtime_resume_host() users just gate their clocks in their runtime
suspend implementation, so the sdhci_runtime_resume_host() is too heavy, we only
need to restore interrupts registers.

The change is something as following:

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 0ad412a..9d5bdde 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -2856,7 +2856,7 @@ int sdhci_runtime_suspend_host(struct sdhci_host *host)
 }
 EXPORT_SYMBOL_GPL(sdhci_runtime_suspend_host);
 
-int sdhci_runtime_resume_host(struct sdhci_host *host)
+static void sdhci_runtime_resume_reinit(struct sdhci_host *host)
 {
 	unsigned long flags;
 	int host_flags = host->flags;
@@ -2880,6 +2880,15 @@ int sdhci_runtime_resume_host(struct sdhci_host *host)
 		sdhci_enable_preset_value(host, true);
 		spin_unlock_irqrestore(&host->lock, flags);
 	}
+}
+
+int sdhci_runtime_resume_host(struct sdhci_host *host, bool power_keeped)
+{
+	unsigned long flags;
+	int host_flags = host->flags;
+
+	if (!power_keeped)
+		sdhci_runtime_resume_reinit(host);
 
 	/* Set the re-tuning expiration flag */
 	if (host->flags & SDHCI_USING_RETUNING_TIMER)


It's ugly, but per my test on marvell BG2Q platforms, this change can improve
the resume latency from 5500us to 11us. Is there any better solution?

Thanks in advance,
Jisheng
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