linux-kernel - [PATCH 4.15 020/122] mmc: dw_mmc: Avoid accessing registers in runtime suspended state

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Message-Id: <20180307191732.271719877@linuxfoundation.org>
Date:   Wed,  7 Mar 2018 11:37:12 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Shawn Lin <shawn.lin@...k-chips.com>,
        Jaehoon Chung <jh80.chung@...sung.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: [PATCH 4.15 020/122] mmc: dw_mmc: Avoid accessing registers in runtime suspended state

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Shawn Lin <shawn.lin@...k-chips.com>

commit 5b43df8b4c1a7f0c3fbf793c9566068e6b1e570c upstream.

cat /sys/kernel/debug/mmc0/regs will hang up the system since
it's in runtime suspended state, so the genpd and biu_clk is
off. This patch fixes this problem by calling pm_runtime_get_sync
to wake it up before reading the registers.

Fixes: e9ed8835e990 ("mmc: dw_mmc: add runtime PM callback")
Cc: <stable@...r.kernel.org>
Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
Reviewed-by: Jaehoon Chung <jh80.chung@...sung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/mmc/host/dw_mmc.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -165,6 +165,8 @@ static int dw_mci_regs_show(struct seq_f
 {
 	struct dw_mci *host = s->private;
 
+	pm_runtime_get_sync(host->dev);
+
 	seq_printf(s, "STATUS:\t0x%08x\n", mci_readl(host, STATUS));
 	seq_printf(s, "RINTSTS:\t0x%08x\n", mci_readl(host, RINTSTS));
 	seq_printf(s, "CMD:\t0x%08x\n", mci_readl(host, CMD));
@@ -172,6 +174,8 @@ static int dw_mci_regs_show(struct seq_f
 	seq_printf(s, "INTMASK:\t0x%08x\n", mci_readl(host, INTMASK));
 	seq_printf(s, "CLKENA:\t0x%08x\n", mci_readl(host, CLKENA));
 
+	pm_runtime_put_autosuspend(host->dev);
+
 	return 0;
 }