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Date:   Tue, 5 May 2020 09:38:11 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Rajendra Nayak <rnayak@...eaurora.org>
Cc:     viresh.kumar@...aro.org, sboyd@...nel.org,
        bjorn.andersson@...aro.org, agross@...nel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mark Brown <broonie@...nel.org>,
        Alok Chauhan <alokc@...eaurora.org>,
        Akash Asthana <akashast@...eaurora.org>,
        linux-spi@...r.kernel.org
Subject: Re: [PATCH v4 6/6] spi: spi-qcom-qspi: Use OPP API to set clk/perf
 state

Hi Rajendra,

On Sun, May 03, 2020 at 05:34:29PM +0530, Rajendra Nayak wrote:
> QSPI needs to vote on a performance state of a power domain depending on
> the clock rate. Add support for it by specifying the perf state/clock rate
> as an OPP table in device tree.
> 
> Signed-off-by: Rajendra Nayak <rnayak@...eaurora.org>
> Cc: Mark Brown <broonie@...nel.org>
> Cc: Alok Chauhan <alokc@...eaurora.org>
> Cc: Akash Asthana <akashast@...eaurora.org>
> Cc: linux-spi@...r.kernel.org
> ---
>  drivers/spi/spi-qcom-qspi.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-qcom-qspi.c b/drivers/spi/spi-qcom-qspi.c
> index 3c4f83b..eb53c00 100644
> --- a/drivers/spi/spi-qcom-qspi.c
> +++ b/drivers/spi/spi-qcom-qspi.c
> @@ -8,6 +8,7 @@
>  #include <linux/of.h>
>  #include <linux/of_platform.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/pm_opp.h>
>  #include <linux/spi/spi.h>
>  #include <linux/spi/spi-mem.h>
>  
> @@ -139,6 +140,8 @@ struct qcom_qspi {
>  	struct device *dev;
>  	struct clk_bulk_data *clks;
>  	struct qspi_xfer xfer;
> +	struct opp_table *opp_table;
> +	bool has_opp_table;
>  	/* Lock to protect xfer and IRQ accessed registers */
>  	spinlock_t lock;
>  };
> @@ -235,7 +238,7 @@ static int qcom_qspi_transfer_one(struct spi_master *master,
>  		speed_hz = xfer->speed_hz;
>  
>  	/* In regular operation (SBL_EN=1) core must be 4x transfer clock */
> -	ret = clk_set_rate(ctrl->clks[QSPI_CLK_CORE].clk, speed_hz * 4);
> +	ret = dev_pm_opp_set_rate(ctrl->dev, speed_hz * 4);
>  	if (ret) {
>  		dev_err(ctrl->dev, "Failed to set core clk %d\n", ret);
>  		return ret;
> @@ -481,6 +484,20 @@ static int qcom_qspi_probe(struct platform_device *pdev)
>  	master->handle_err = qcom_qspi_handle_err;
>  	master->auto_runtime_pm = true;
>  
> +	ctrl->opp_table = dev_pm_opp_set_clkname(&pdev->dev, "core");
> +	if (IS_ERR(ctrl->opp_table)) {
> +		ret = PTR_ERR(ctrl->opp_table);
> +		goto exit_probe_master_put;
> +	}
> +	/* OPP table is optional */
> +	ret = dev_pm_opp_of_add_table(&pdev->dev);
> +	if (!ret) {
> +		ctrl->has_opp_table = true;
> +	} else if (ret != -ENODEV) {
> +		dev_err(&pdev->dev, "invalid OPP table in device tree\n");
> +		goto exit_probe_master_put;
> +	}
> +
>  	pm_runtime_enable(dev);
>  
>  	ret = spi_register_master(master);
> @@ -488,6 +505,9 @@ static int qcom_qspi_probe(struct platform_device *pdev)
>  		return 0;
>  
>  	pm_runtime_disable(dev);
> +	if (ctrl->has_opp_table)
> +		dev_pm_opp_of_remove_table(&pdev->dev);
> +	dev_pm_opp_put_clkname(ctrl->opp_table);
>  
>  exit_probe_master_put:
>  	spi_master_put(master);
> @@ -498,6 +518,11 @@ static int qcom_qspi_probe(struct platform_device *pdev)
>  static int qcom_qspi_remove(struct platform_device *pdev)
>  {
>  	struct spi_master *master = platform_get_drvdata(pdev);
> +	struct qcom_qspi *ctrl = spi_master_get_devdata(master);
> +
> +	if (ctrl->has_opp_table)
> +		dev_pm_opp_of_remove_table(&pdev->dev);
> +	dev_pm_opp_put_clkname(ctrl->opp_table);

IIUC there can still be active transfers before the controller is
unregistered. If that is correct the above should be done after the
spi_unregister_master() call below.

>  
>  	/* Unregister _before_ disabling pm_runtime() so we stop transfers */
>  	spi_unregister_master(master);
> @@ -512,6 +537,8 @@ static int __maybe_unused qcom_qspi_runtime_suspend(struct device *dev)
>  	struct spi_master *master = dev_get_drvdata(dev);
>  	struct qcom_qspi *ctrl = spi_master_get_devdata(master);
>  
> +	/* Drop the performance state vote */
> +	dev_pm_opp_set_rate(dev, 0);
>  	clk_bulk_disable_unprepare(QSPI_NUM_CLKS, ctrl->clks);
>  
>  	return 0;

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