Re: [PATCH 2/4] drm/msm: dsi: Use OPP API to set clk/perf state

[Matthias Kaehlcke <mka@chromium.org>]

On Tue, Jun 30, 2020 at 05:26:14PM +0530, Rajendra Nayak wrote:
> On SDM845 DSI needs to express a perforamnce state

nit: performance

> requirement on a power domain depending on the clock rates.
> Use OPP table from DT to register with OPP framework and use
> dev_pm_opp_set_rate() to set the clk/perf state.
> 
> Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
> ---
>  drivers/gpu/drm/msm/dsi/dsi.h      |  2 ++
>  drivers/gpu/drm/msm/dsi/dsi_cfg.c  |  4 +--
>  drivers/gpu/drm/msm/dsi/dsi_host.c | 58 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 62 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/dsi.h b/drivers/gpu/drm/msm/dsi/dsi.h
> index 4de771d..ba7583c 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi.h
> +++ b/drivers/gpu/drm/msm/dsi/dsi.h
> @@ -180,10 +180,12 @@ int msm_dsi_runtime_suspend(struct device *dev);
>  int msm_dsi_runtime_resume(struct device *dev);
>  int dsi_link_clk_set_rate_6g(struct msm_dsi_host *msm_host);
>  int dsi_link_clk_set_rate_v2(struct msm_dsi_host *msm_host);
> +int dsi_link_clk_set_rate_6g_v2(struct msm_dsi_host *msm_host);
>  int dsi_link_clk_enable_6g(struct msm_dsi_host *msm_host);
>  int dsi_link_clk_enable_v2(struct msm_dsi_host *msm_host);
>  void dsi_link_clk_disable_6g(struct msm_dsi_host *msm_host);
>  void dsi_link_clk_disable_v2(struct msm_dsi_host *msm_host);
> +void dsi_link_clk_disable_6g_v2(struct msm_dsi_host *msm_host);
>  int dsi_tx_buf_alloc_6g(struct msm_dsi_host *msm_host, int size);
>  int dsi_tx_buf_alloc_v2(struct msm_dsi_host *msm_host, int size);
>  void *dsi_tx_buf_get_6g(struct msm_dsi_host *msm_host);
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_cfg.c b/drivers/gpu/drm/msm/dsi/dsi_cfg.c
> index 813d69d..773c4fe 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_cfg.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_cfg.c
> @@ -210,9 +210,9 @@ static const struct msm_dsi_host_cfg_ops msm_dsi_6g_host_ops = {
>  };
>  
>  static const struct msm_dsi_host_cfg_ops msm_dsi_6g_v2_host_ops = {
> -	.link_clk_set_rate = dsi_link_clk_set_rate_6g,
> +	.link_clk_set_rate = dsi_link_clk_set_rate_6g_v2,
>  	.link_clk_enable = dsi_link_clk_enable_6g,
> -	.link_clk_disable = dsi_link_clk_disable_6g,
> +	.link_clk_disable = dsi_link_clk_disable_6g_v2,
>  	.clk_init_ver = dsi_clk_init_6g_v2,
>  	.tx_buf_alloc = dsi_tx_buf_alloc_6g,
>  	.tx_buf_get = dsi_tx_buf_get_6g,
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index 11ae5b8..890531c 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -14,6 +14,7 @@
>  #include <linux/of_graph.h>
>  #include <linux/of_irq.h>
>  #include <linux/pinctrl/consumer.h>
> +#include <linux/pm_opp.h>
>  #include <linux/regmap.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/spinlock.h>
> @@ -111,6 +112,9 @@ struct msm_dsi_host {
>  	struct clk *pixel_clk_src;
>  	struct clk *byte_intf_clk;
>  
> +	struct opp_table *opp_table;
> +	bool has_opp_table;
> +
>  	u32 byte_clk_rate;
>  	u32 pixel_clk_rate;
>  	u32 esc_clk_rate;
> @@ -537,6 +541,38 @@ int dsi_link_clk_set_rate_6g(struct msm_dsi_host *msm_host)
>  	return 0;
>  }
>  
> +int dsi_link_clk_set_rate_6g_v2(struct msm_dsi_host *msm_host)
> +{
> +	int ret;
> +	struct device *dev = &msm_host->pdev->dev;
> +
> +	DBG("Set clk rates: pclk=%d, byteclk=%d",
> +		msm_host->mode->clock, msm_host->byte_clk_rate);
> +
> +	ret = dev_pm_opp_set_rate(dev, msm_host->byte_clk_rate);
> +	if (ret) {
> +		pr_err("%s: dev_pm_opp_set_rate failed %d\n", __func__, ret);
> +		return ret;
> +	}
> +
> +	ret = clk_set_rate(msm_host->pixel_clk, msm_host->pixel_clk_rate);
> +	if (ret) {
> +		pr_err("%s: Failed to set rate pixel clk, %d\n", __func__, ret);
> +		return ret;
> +	}
> +
> +	if (msm_host->byte_intf_clk) {
> +		ret = clk_set_rate(msm_host->byte_intf_clk,
> +				   msm_host->byte_clk_rate / 2);
> +		if (ret) {
> +			pr_err("%s: Failed to set rate byte intf clk, %d\n",
> +			       __func__, ret);
> +			return ret;
> +		}
> +	}
> +
> +	return 0;
> +}

xThis function is essentially the same as dsi_link_clk_set_rate_6g(),
except for the use of dev_pm_opp_set_rate() instead of clk_set_rate().

IIUC dev_pm_opp_set_rate() just calls clk_set_rate() if the device has
no OPP table. If that's correct you could just call dev_pm_opp_set_rate()
in dsi_link_clk_set_rate_6g().

	/*
    	* For IO devices which require an OPP on some platforms/SoCs
    	* while just needing to scale the clock on some others
    	* we look for empty OPP tables with just a clock handle and
    	* scale only the clk. This makes dev_pm_opp_set_rate()
	* equivalent to a clk_set_rate()
	*/
	if (!_get_opp_count(opp_table)) {
		ret = _generic_set_opp_clk_only(dev, clk, freq);
		goto put_opp_table;
	}

https://elixir.bootlin.com/linux/v5.7.6/source/drivers/opp/core.c#L855

>  int dsi_link_clk_enable_6g(struct msm_dsi_host *msm_host)
>  {
> @@ -665,6 +701,13 @@ void dsi_link_clk_disable_6g(struct msm_dsi_host *msm_host)
>  	clk_disable_unprepare(msm_host->byte_clk);
>  }
>  
> +void dsi_link_clk_disable_6g_v2(struct msm_dsi_host *msm_host)
> +{
> +	/* Drop the performance state vote */
> +	dev_pm_opp_set_rate(&msm_host->pdev->dev, 0);

Couldn't you just do this in dsi_link_clk_disable_6g() ?

> +	dsi_link_clk_disable_6g(msm_host);
> +}
> +