Re: [PATCH 2/4] mmc: sdhci-of-arasan: Control clock for accessing syscon

Heiko Stübner
2016-08-29T08:25:20Z

Hi Shawn,

Am Montag, 29. August 2016, 16:02:57 schrieb Shawn Lin:
> In the eariler commit 65820199272d ("Documentation: mmc:
> sdhci-of-arasan: Add soc-ctl-syscon for corecfg regs"), we
> introduced syscon to control corecfg_* stuff provided by
> arasan. But given that we may need to ungate the clock for
> accessing corecfg_*, it not so perfect as it depends on
> whether specific clock driver disables it if not referenced.
> Meanwhile, if we don't need arasan contoller to work anymore,
> there is no reason to still enable it. So let's control this
> clock when needed.
>
> Signed-off-by: Shawn Lin <shawn.lin-TNX95d0MmH7DzftRWevZcw@public.gmane.org>
> ---
>
> drivers/mmc/host/sdhci-of-arasan.c | 25 ++++++++++++++++++++++---
> 1 file changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-of-arasan.c
> b/drivers/mmc/host/sdhci-of-arasan.c index 0b3a9cf..7ae3ae4 100644
> --- a/drivers/mmc/host/sdhci-of-arasan.c
> +++ b/drivers/mmc/host/sdhci-of-arasan.c
> @@ -78,6 +78,7 @@ struct sdhci_arasan_soc_ctl_map {
> * struct sdhci_arasan_data
> * @host: Pointer to the main SDHCI host structure.
> * @clk_ahb: Pointer to the AHB clock
> + * @clk_syscon: Pointer to the optional clock for accessing syscon
> * @phy: Pointer to the generic phy
> * @is_phy_on: True if the PHY is on; false if not.
> * @sdcardclk_hw: Struct for the clock we might provide to a PHY.
> @@ -88,6 +89,7 @@ struct sdhci_arasan_soc_ctl_map {
> struct sdhci_arasan_data {
> struct sdhci_host *host;
> struct clk *clk_ahb;
> + struct clk *clk_syscon;
> struct phy *phy;
> bool is_phy_on;
>
> @@ -290,6 +292,7 @@ static int sdhci_arasan_suspend(struct device *dev)
>
> clk_disable(pltfm_host->clk);
> clk_disable(sdhci_arasan->clk_ahb);
> + clk_disable(sdhci_arasan->clk_syscon);
>
> return 0;
> }
> @@ -309,6 +312,12 @@ static int sdhci_arasan_resume(struct device *dev)
> struct sdhci_arasan_data *sdhci_arasan = sdhci_pltfm_priv(pltfm_host);
> int ret;
>
> + ret = clk_enable(sdhci_arasan->clk_syscon);
> + if (ret) {
> + dev_err(dev, "Cannot enable syscon clock.\n");
> + return ret;
> + }
> +
> ret = clk_enable(sdhci_arasan->clk_ahb);
> if (ret) {
> dev_err(dev, "Cannot enable AHB clock.\n");
> @@ -528,26 +537,33 @@ static int sdhci_arasan_probe(struct platform_device
> *pdev) ret);
> goto err_pltfm_free;
> }
> +
> + sdhci_arasan->clk_syscon = devm_clk_get(&pdev->dev,
> + "clk_syscon");
> + if (clk_prepare_enable(sdhci_arasan->clk_syscon)) {
> + dev_err(&pdev->dev, "Unable to enable syscon clock.\n");
> + goto err_pltfm_free;
> + }

doesn't look very "optional" to me.
clk_get specifies:
"Returns a struct clk corresponding to the clock producer, or
valid IS_ERR() condition containing errno."

So later clk_* on that err_ptr will produce failures and the clock-framework
could also request deferal.

Heiko

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