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

[Matthias Brugger]

On 14/10/2020 05:06, Nicolas Boichat wrote:
> On Wed, Oct 14, 2020 at 10:29 AM Wenbin Mei <wenbin.mei@xxxxxxxxxxxx> wrote:
> > 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@xxxxxxxxxxxx>
> > > > ---
> > > >    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.
>
> Yes I guess the constants end up in .rodata (or similar section), but
> I'm not sure if this is absolutely guaranteed.
>
> In any case, this is a commonly used pattern, so I'd hope it's fine
> (just a sample, there are more):
> https://elixir.bootlin.com/linux/latest/source/drivers/pci/controller/dwc/pcie-qcom.c#L266
> https://elixir.bootlin.com/linux/latest/source/sound/soc/codecs/wm8994.c#L4638
> https://elixir.bootlin.com/linux/latest/source/drivers/mfd/madera-core.c#L467
> https://elixir.bootlin.com/linux/latest/source/drivers/gpio/gpio-dwapb.c#L675

Alright, then this looks good, sorry for the noise!
Matthias