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 for linux-mtd@lists.infradead.org; Thu, 05 Apr 2018 11:27:06 +0000
Subject: Re: [PATCH 1/1] mtd:nand:fix memory leak
To: Boris Brezillon <boris.brezillon@bootlin.com>,
 Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Xidong Wang <wangxidong_97@163.com>, Mans Rullgard <mans@mansr.com>,
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 Cyrille Pitchen <cyrille.pitchen@wedev4u.fr>,
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 David Woodhouse <dwmw2@infradead.org>,
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From: Marc Gonzalez <marc.w.gonzalez@free.fr>
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Date: Thu, 5 Apr 2018 13:26:31 +0200
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On 05/04/2018 11:54, Boris Brezillon wrote:

> On Thu, 5 Apr 2018 11:12:11 +0200, Marc Gonzalez wrote:
> 
>> I was not aware that clk_get() allocated memory, and required clk_put()
>> for cleanup. IIRC, I looked at Documentation/clk.txt
>>
>> On tango, clocks are configured by the boot loader. The existing clk driver
>> provides only read access to various clocks -- except the CPU clock, which
>> can be changed by tweaking a post-divider. Tweaking the PLLs requires much
>> more complex code. The boot loader enables every clock, and Linux has no
>> way to gate any of them.
> 
> Well, even if that's not supported today, it's always a good practice
> to retain reference and prepare/enable clks your HW depends on. This
> change should be harmless and when/if you someday decide to provide a
> way to gate clks, it will work out of the box.

IIUC, you're saying:
1) use devm_clk_get() instead of clk_get() to solve the memory leak
2) call clk_prepare_enable() before clk_get_rate() even if the former is a no-op today

The following patch implements these suggestions.
(Only compile-tested)

diff --git a/drivers/mtd/nand/tango_nand.c b/drivers/mtd/nand/tango_nand.c
index c5bee00b7f5e..39d190b7521f 100644
--- a/drivers/mtd/nand/tango_nand.c
+++ b/drivers/mtd/nand/tango_nand.c
@@ -643,7 +643,7 @@ static int tango_nand_probe(struct platform_device *pdev)
 
        writel_relaxed(MODE_RAW, nfc->pbus_base + PBUS_PAD_MODE);
 
-       clk = clk_get(&pdev->dev, NULL);
+       clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(clk))
                return PTR_ERR(clk);
 
@@ -651,6 +651,10 @@ static int tango_nand_probe(struct platform_device *pdev)
        if (IS_ERR(nfc->chan))
                return PTR_ERR(nfc->chan);
 
+       err = clk_prepare_enable(clk);
+       if (err)
+               return err;
+
        platform_set_drvdata(pdev, nfc);
        nand_hw_control_init(&nfc->hw);
        nfc->freq_kHz = clk_get_rate(clk) / 1000;