mmc: sdhci-st: Handle interconnect clock

Some ST platforms contain interconnect (ICN) clocks which must be handed
correctly in order to obtain full functionality of a given IP.  In this
case, if the ICN clocks are not handled properly by the ST SDHCI driver
MMC will break and the following output can be observed:

    [   13.916949] mmc0: Timeout waiting for hardware interrupt.
    [   13.922349] sdhci: =========== REGISTER DUMP (mmc0)===========
    [   13.928175] sdhci: Sys addr: 0x00000000 | Version:  0x00001002
    [   13.933999] sdhci: Blk size: 0x00007040 | Blk cnt:  0x00000001
    [   13.939825] sdhci: Argument: 0x00fffff0 | Trn mode: 0x00000013
    [   13.945650] sdhci: Present:  0x1fff0206 | Host ctl: 0x00000011
    [   13.951475] sdhci: Power:    0x0000000f | Blk gap:  0x00000080
    [   13.957300] sdhci: Wake-up:  0x00000000 | Clock:    0x00003f07
    [   13.963126] sdhci: Timeout:  0x00000004 | Int stat: 0x00000000
    [   13.968952] sdhci: Int enab: 0x02ff008b | Sig enab: 0x02ff008b
    [   13.974777] sdhci: AC12 err: 0x00000000 | Slot int: 0x00000000
    [   13.980602] sdhci: Caps:     0x21ed3281 | Caps_1:   0x00000000
    [   13.986428] sdhci: Cmd:      0x0000063a | Max curr: 0x00000000
    [   13.992252] sdhci: Host ctl2: 0x00000000
    [   13.996166] sdhci: ADMA Err: 0x00000000 | ADMA Ptr: 0x7c048200
    [   14.001990] sdhci: ===========================================
    [   14.009802] mmc0: Got data interrupt 0x02000000 even though no data operation was in progress.

A decent point was raised about minimising the use of a local variable that
we 'could' do without.  I've chosen consistency over the possibility of
reducing the local variable count by 1.  Thinking that it's more important
for the code to be grouped and authoured in a similar manner/style for
greater maintainability/readability.

Cc: stable@vger.kernel.org
Tested-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-st.c

@@ -28,6 +28,7 @@
 
 struct st_mmc_platform_data {
 	struct  reset_control *rstc;
+	struct  clk *icnclk;
 	void __iomem *top_ioaddr;
 };
 
@@ -353,7 +354,7 @@ static int sdhci_st_probe(struct platform_device *pdev)
 	struct sdhci_host *host;
 	struct st_mmc_platform_data *pdata;
 	struct sdhci_pltfm_host *pltfm_host;
-	struct clk *clk;
+	struct clk *clk, *icnclk;
 	int ret = 0;
 	u16 host_version;
 	struct resource *res;
@@ -365,6 +366,11 @@ static int sdhci_st_probe(struct platform_device *pdev)
 		return PTR_ERR(clk);
 	}
 
+	/* ICN clock isn't compulsory, but use it if it's provided. */
+	icnclk = devm_clk_get(&pdev->dev, "icn");
+	if (IS_ERR(icnclk))
+		icnclk = NULL;
+
 	rstc = devm_reset_control_get(&pdev->dev, NULL);
 	if (IS_ERR(rstc))
 		rstc = NULL;
@@ -389,6 +395,7 @@ static int sdhci_st_probe(struct platform_device *pdev)
 	}
 
 	clk_prepare_enable(clk);
+	clk_prepare_enable(icnclk);
 
 	/* Configure the FlashSS Top registers for setting eMMC TX/RX delay */
 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
@@ -400,6 +407,7 @@ static int sdhci_st_probe(struct platform_device *pdev)
 	}
 
 	pltfm_host->clk = clk;
+	pdata->icnclk = icnclk;
 
 	/* Configure the Arasan HC inside the flashSS */
 	st_mmcss_cconfig(np, host);
@@ -422,6 +430,7 @@ static int sdhci_st_probe(struct platform_device *pdev)
 	return 0;
 
 err_out:
+	clk_disable_unprepare(icnclk);
 	clk_disable_unprepare(clk);
 err_of:
 	sdhci_pltfm_free(pdev);
@@ -442,6 +451,8 @@ static int sdhci_st_remove(struct platform_device *pdev)
 
 	ret = sdhci_pltfm_unregister(pdev);
 
+	clk_disable_unprepare(pdata->icnclk);
+
 	if (rstc)
 		reset_control_assert(rstc);
 
@@ -462,6 +473,7 @@ static int sdhci_st_suspend(struct device *dev)
 	if (pdata->rstc)
 		reset_control_assert(pdata->rstc);
 
+	clk_disable_unprepare(pdata->icnclk);
 	clk_disable_unprepare(pltfm_host->clk);
 out:
 	return ret;
@@ -475,6 +487,7 @@ static int sdhci_st_resume(struct device *dev)
 	struct device_node *np = dev->of_node;
 
 	clk_prepare_enable(pltfm_host->clk);
+	clk_prepare_enable(pdata->icnclk);
 
 	if (pdata->rstc)
 		reset_control_deassert(pdata->rstc);