Re: [PATCH v3 4/4] mmc: mediatek: Add subsys clock control for MT8192 msdc

[Nicolas Boichat <drinkcat@chromium.org>]

On Wed, Sep 30, 2020 at 4:31 PM Wenbin Mei <wenbin.mei@mediatek.com> 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@mediatek.com>
> ---
>  drivers/mmc/host/mtk-sd.c | 77 ++++++++++++++++++++++++++++++---------
>  1 file changed, 59 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/mmc/host/mtk-sd.c b/drivers/mmc/host/mtk-sd.c
> index a704745e5882..9a1422955593 100644
> --- a/drivers/mmc/host/mtk-sd.c
> +++ b/drivers/mmc/host/mtk-sd.c
> @@ -425,6 +425,8 @@ struct msdc_host {
>         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 */
> +       struct clk *sys_clk_cg; /* msdc subsys clock control gate */
> +       struct clk_bulk_data bulk_clks[3];      /* pclk, axi, ahb clock control gate */
>         u32 mclk;               /* mmc subsystem clock frequency */
>         u32 src_clk_freq;       /* source clock frequency */
>         unsigned char timing;
> @@ -784,6 +786,8 @@ static void msdc_set_busy_timeout(struct msdc_host *host, u64 ns, u64 clks)
>
>  static void msdc_gate_clock(struct msdc_host *host)
>  {
> +       clk_bulk_disable_unprepare(ARRAY_SIZE(host->bulk_clks),
> +                                  host->bulk_clks);
>         clk_disable_unprepare(host->src_clk_cg);
>         clk_disable_unprepare(host->src_clk);
>         clk_disable_unprepare(host->bus_clk);
> @@ -792,10 +796,17 @@ static void msdc_gate_clock(struct msdc_host *host)
>
>  static void msdc_ungate_clock(struct msdc_host *host)
>  {
> +       int ret;
> +
>         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);
> +       ret = clk_bulk_prepare_enable(ARRAY_SIZE(host->bulk_clks),
> +                                     host->bulk_clks);
> +       if (ret)
> +               dev_dbg(host->dev, "enable clks failed!\n");

dev_err looks a lot more appropriate. Also, don't you want to exit the
function in that case, rather than going to the while loop below where
you may get stuck?

> +
>         while (!(readl(host->base + MSDC_CFG) & MSDC_CFG_CKSTB))
>                 cpu_relax();
>  }
> @@ -2366,6 +2377,52 @@ static void msdc_of_property_parse(struct platform_device *pdev,
>                 host->cqhci = false;
>  }
>
> +static int msdc_of_clock_parse(struct platform_device *pdev,
> +                              struct msdc_host *host)
> +{
> +       struct clk *clk;
> +
> +       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(&pdev->dev, "bus_clk");
> +       if (IS_ERR(host->bus_clk))
> +               host->bus_clk = NULL;

Use devm_clk_get_optional instead (ditto for the next 2).

> +
> +       /*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))
> +               host->src_clk_cg = NULL;
> +
> +       host->sys_clk_cg = devm_clk_get(&pdev->dev, "sys_cg");
> +       if (IS_ERR(host->sys_clk_cg))
> +               host->sys_clk_cg = NULL;
> +       else
> +               clk_prepare_enable(host->sys_clk_cg);

This doesn't need to be in an else branch, calling clk_prepare_enable
on a NULL clock is fine.

However, is it expected that this clock is turned on forever after
probe?! At the very least, the clock should be disabled in
msdc_drv_remove, but, really, I think it should be enabled as needed,
like the other clocks, in msdc_gate_clock?

> +
> +       clk = devm_clk_get(&pdev->dev, "pclk_cg");
> +       if (IS_ERR(clk))
> +               clk = NULL;
> +       host->bulk_clks[0].clk = clk;
> +
> +       clk = devm_clk_get(&pdev->dev, "axi_cg");
> +       if (IS_ERR(clk))
> +               clk = NULL;
> +       host->bulk_clks[1].clk = clk;
> +
> +       clk = devm_clk_get(&pdev->dev, "ahb_cg");
> +       if (IS_ERR(clk))
> +               clk = NULL;
> +       host->bulk_clks[2].clk = clk;

Use devm_clk_bulk_get_optional for these 3.

> +
> +       return 0;
> +}
> +
>  static int msdc_drv_probe(struct platform_device *pdev)
>  {
>         struct mmc_host *mmc;
> @@ -2405,25 +2462,9 @@ static int msdc_drv_probe(struct platform_device *pdev)
>         if (ret)
>                 goto host_free;
>
> -       host->src_clk = devm_clk_get(&pdev->dev, "source");
> -       if (IS_ERR(host->src_clk)) {
> -               ret = PTR_ERR(host->src_clk);
> -               goto host_free;
> -       }
> -
> -       host->h_clk = devm_clk_get(&pdev->dev, "hclk");
> -       if (IS_ERR(host->h_clk)) {
> -               ret = PTR_ERR(host->h_clk);
> +       ret = msdc_of_clock_parse(pdev, host);
> +       if (ret)
>                 goto host_free;
> -       }
> -
> -       host->bus_clk = devm_clk_get(&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(&pdev->dev, "source_cg");
> -       if (IS_ERR(host->src_clk_cg))
> -               host->src_clk_cg = NULL;
>
>         host->reset = devm_reset_control_get_optional_exclusive(&pdev->dev,
>                                                                 "hrst");
> --
> 2.18.0