linux-kernel - Re: [PATCH v6 4/4] mmc: mediatek: Add subsys clock control for MT8192 msdc

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Date:   Wed, 14 Oct 2020 10:28:50 +0800
From:   Wenbin Mei <wenbin.mei@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>
CC:     Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Chaotian Jing <chaotian.jing@...iatek.com>,
        <linux-mmc@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <srv_heupstream@...iatek.com>
Subject: Re: [PATCH v6 4/4] mmc: mediatek: Add subsys clock control for
 MT8192 msdc

On Tue, 2020-10-13 at 17:10 +0200, Matthias Brugger wrote:
> 
> On 12/10/2020 14:45, Wenbin Mei wrote:
> > MT8192 msdc is an independent sub system, we need control more bus
> > clocks for it.
> > Add support for the additional subsys clocks to allow it to be
> > configured appropriately.
> > 
> > Signed-off-by: Wenbin Mei <wenbin.mei@...iatek.com>
> > ---
> >   drivers/mmc/host/mtk-sd.c | 74 +++++++++++++++++++++++++++++----------
> >   1 file changed, 56 insertions(+), 18 deletions(-)
> > 
> > diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
> > index a704745e5882..c7df7510f120 100644
> > --- a/drivers/mmc/host/mtk-sd.c
> > +++ b/drivers/mmc/host/mtk-sd.c
> [...]
> > +static int msdc_of_clock_parse(struct platform_device *pdev,
> > +			       struct msdc_host *host)
> > +{
> > +	int ret;
> > +
> > +	host->src_clk = devm_clk_get(&pdev->dev, "source");
> > +	if (IS_ERR(host->src_clk))
> > +		return PTR_ERR(host->src_clk);
> > +
> > +	host->h_clk = devm_clk_get(&pdev->dev, "hclk");
> > +	if (IS_ERR(host->h_clk))
> > +		return PTR_ERR(host->h_clk);
> > +
> > +	host->bus_clk = devm_clk_get_optional(&pdev->dev, "bus_clk");
> > +	if (IS_ERR(host->bus_clk))
> > +		host->bus_clk = NULL;
> > +
> > +	/*source clock control gate is optional clock*/
> > +	host->src_clk_cg = devm_clk_get_optional(&pdev->dev, "source_cg");
> > +	if (IS_ERR(host->src_clk_cg))
> > +		host->src_clk_cg = NULL;
> > +
> > +	host->sys_clk_cg = devm_clk_get_optional(&pdev->dev, "sys_cg");
> > +	if (IS_ERR(host->sys_clk_cg))
> > +		host->sys_clk_cg = NULL;
> > +
> > +	/* If present, always enable for this clock gate */
> > +	clk_prepare_enable(host->sys_clk_cg);
> > +
> > +	host->bulk_clks[0].id = "pclk_cg";
> > +	host->bulk_clks[1].id = "axi_cg";
> > +	host->bulk_clks[2].id = "ahb_cg";
> 
> That looks at least suspicious. The pointers of id point to some strings defined 
> in the function. Aren't they out of scope once msdc_of_clock_parse() has returned?
> 
These constants are not in stack range, so they will not be lost.
And I have confirmed it after msdc_of_clock_parse() has returned, these
ids still exist.

> Regards,
> Matthias