Re: [PATCH 2/2] mmc: mediatek: add bus_clk control

Chaotian Jing
2018-09-29T02:39:42Z

On Sat, 2018-09-29 at 01:28 +0800, Sean Wang wrote:
> Hi,
>
> On Fri, 2018-09-28 at 19:40 +0800, Chaotian Jing wrote:
> > when gate MSDC0_HCLK, access register will hang, even the MSDC driver
> > will never accessing register after HCLK was gated, but for safety, need
> > gate the bus_clk(which used to access register) too.
> >
> > Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>
> > ---
> > drivers/mmc/host/mtk-sd.c | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
> > index 0484138..1c1c967 100644
> > --- a/drivers/mmc/host/mtk-sd.c
> > +++ b/drivers/mmc/host/mtk-sd.c
> > @@ -387,6 +387,7 @@ struct msdc_host {
> >
> > struct clk *src_clk; /* msdc source clock */
> > struct clk *h_clk; /* msdc h_clk */
> > + struct clk *bus_clk; /* bus clock which used to access register */
> > struct clk *src_clk_cg; /* msdc source clock control gate */
> > u32 mclk; /* mmc subsystem clock frequency */
> > u32 src_clk_freq; /* source clock frequency */
> > @@ -660,12 +661,14 @@ static void msdc_gate_clock(struct msdc_host *host)
> > {
> > clk_disable_unprepare(host->src_clk_cg);
> > clk_disable_unprepare(host->src_clk);
> > + clk_disable_unprepare(host->bus_clk);
> > clk_disable_unprepare(host->h_clk);
> > }
> >
> > static void msdc_ungate_clock(struct msdc_host *host)
> > {
> > clk_prepare_enable(host->h_clk);
> > + clk_prepare_enable(host->bus_clk);
> > clk_prepare_enable(host->src_clk);
> > clk_prepare_enable(host->src_clk_cg);
> > while (!(readl(host->base + MSDC_CFG) & MSDC_CFG_CKSTB))
> > @@ -1900,6 +1903,9 @@ static int msdc_drv_probe(struct platform_device *pdev)
> > goto host_free;
> > }
> >
> > + host->bus_clk = devm_clk_get(&pdev->dev, "bus_clk");
> > + if (IS_ERR(host->bus_clk))
> > + host->bus_clk = NULL;
>
> The implementation would cause all SoCs to treat the bus_clk as the optional.
> It seems you should add a flag to see what SoC requires the bus_clk to successfully access the related registers.

> Yes, but is no harm to other SoCs, just like the handle of "source_cg"
> > /*source clock control gate is optional clock*/
> > host->src_clk_cg = devm_clk_get(&pdev->dev, "source_cg");
> > if (IS_ERR(host->src_clk_cg))
>
>