Re: [PATCH] iommu/qcom: add optional clock for TLB invalidate

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Sat 09 May 06:08 PDT 2020, Shawn Guo wrote:

> On some SoCs like MSM8939 with A405 adreno, there is a gfx_tbu clock
> needs to be on while doing TLB invalidate. Otherwise, TLBSYNC status
> will not be correctly reflected, causing the system to go into a bad
> state.  Add it as an optional clock, so that platforms that have this
> clock can pass it over DT.
> 
> Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
> ---
>  drivers/iommu/qcom_iommu.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/iommu/qcom_iommu.c b/drivers/iommu/qcom_iommu.c
> index 0e2a96467767..2f6c6da7d540 100644
> --- a/drivers/iommu/qcom_iommu.c
> +++ b/drivers/iommu/qcom_iommu.c
> @@ -45,6 +45,7 @@ struct qcom_iommu_dev {
>  	struct device		*dev;
>  	struct clk		*iface_clk;
>  	struct clk		*bus_clk;
> +	struct clk		*tlb_clk;
>  	void __iomem		*local_base;
>  	u32			 sec_id;
>  	u8			 num_ctxs;
> @@ -643,11 +644,20 @@ static int qcom_iommu_enable_clocks(struct qcom_iommu_dev *qcom_iommu)
>  		return ret;
>  	}
>  
> +	ret = clk_prepare_enable(qcom_iommu->tlb_clk);
> +	if (ret) {
> +		dev_err(qcom_iommu->dev, "Couldn't enable tlb_clk\n");
> +		clk_disable_unprepare(qcom_iommu->bus_clk);
> +		clk_disable_unprepare(qcom_iommu->iface_clk);
> +		return ret;
> +	}

Seems this is an excellent opportunity to replace
qcom_iommu_enable_clocks() to clk_bulk_prepare_enable() and disable,
respectively.

> +
>  	return 0;
>  }
>  
>  static void qcom_iommu_disable_clocks(struct qcom_iommu_dev *qcom_iommu)
>  {
> +	clk_disable_unprepare(qcom_iommu->tlb_clk);
>  	clk_disable_unprepare(qcom_iommu->bus_clk);
>  	clk_disable_unprepare(qcom_iommu->iface_clk);
>  }
> @@ -839,6 +849,12 @@ static int qcom_iommu_device_probe(struct platform_device *pdev)
>  		return PTR_ERR(qcom_iommu->bus_clk);
>  	}
>  
> +	qcom_iommu->tlb_clk = devm_clk_get(dev, "tlb");

Wouldn't "tbu" be a better name for this clock? Given that seems the
actually be the hardware block you're clocking.


That said, I thought we used device links and pm_runtime to ensure that
the TBUs are powered and clocked...

Regards,
Bjorn

> +	if (IS_ERR(qcom_iommu->tlb_clk)) {
> +		dev_dbg(dev, "failed to get tlb clock\n");
> +		qcom_iommu->tlb_clk = NULL;
> +	}
> +
>  	if (of_property_read_u32(dev->of_node, "qcom,iommu-secure-id",
>  				 &qcom_iommu->sec_id)) {
>  		dev_err(dev, "missing qcom,iommu-secure-id property\n");
> -- 
> 2.17.1
> 
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