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Date:   Fri, 7 Feb 2020 16:42:22 -0800
From:   Matthias Kaehlcke <mka@chromium.org>
To:     Pradeep P V K <ppvk@codeaurora.org>
Cc:     adrian.hunter@intel.com, robh+dt@kernel.org,
        ulf.hansson@linaro.org, asutoshd@codeaurora.org,
        stummala@codeaurora.org, sayalil@codeaurora.org,
        rampraka@codeaurora.org, vbadigan@codeaurora.org, sboyd@kernel.org,
        georgi.djakov@linaro.org, linux-mmc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        devicetree@vger.kernel.org, agross@kernel.org,
        linux-mmc-owner@vger.kernel.org,
        Subhash Jadavani <subhashj@codeaurora.org>
Subject: Re: [RFC v3 1/2] mmc: sdhci-msm: Add interconnect bus bandwidth
 scaling support
Message-ID: <20200208004222.GC18972@google.com>
References: <1581086695-16645-1-git-send-email-ppvk@codeaurora.org>
 <1581086695-16645-2-git-send-email-ppvk@codeaurora.org>
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Hi Pradeep,

On Fri, Feb 07, 2020 at 08:14:54PM +0530, Pradeep P V K wrote:
> Add interconnect bandwidths for SDHC driver using OPP framework that
> is required by SDHC driver based on the clock frequency and bus width
> of the card. Otherwise, the system clocks may run at minimum clock
> speed and thus affecting the performance.
> 
> This change is based on Georgi Djakov [RFC]
> (https://lkml.org/lkml/2018/10/11/499) and
> 
> Saravana Kannan [PATCH v6]
> (https://lkml.org/lkml/2019/12/6/740)
> 
> change from RFC v2 -> v3 changes:
> - Modified interconnect bandwidth support using OPP framework.
> - Addressed review comments on v2.
> 
> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
> Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
> Signed-off-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>
> Co-developed-by: Pradeep P V K <ppvk@codeaurora.org>
> Signed-off-by: Pradeep P V K <ppvk@codeaurora.org>
> ---
>  drivers/mmc/host/sdhci-msm.c | 251 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 247 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index 71f29ba..f061cd8 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -11,8 +11,10 @@
>  #include <linux/mmc/mmc.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/slab.h>
> +#include <linux/interconnect.h>
>  #include <linux/iopoll.h>
>  #include <linux/regulator/consumer.h>
> +#include <linux/pm_opp.h>
>  
>  #include "sdhci-pltfm.h"
>  
> @@ -229,6 +231,14 @@ struct sdhci_msm_variant_info {
>  	const struct sdhci_msm_offset *offset;
>  };
>  
> +struct sdhci_msm_bus_vote_data {
> +
> +	struct icc_path *sdhc_to_ddr;
> +	struct icc_path *cpu_to_sdhc;
> +	bool skip_bus_bw_voting;

nit: the name is somewhat redundant given the name of the containing
struct. 'skip_vote' or 'skip_voting' would be sufficient IMO.

> +	u32 curr_freq;
> +};
> +
>  struct sdhci_msm_host {
>  	struct platform_device *pdev;
>  	void __iomem *core_mem;	/* MSM SDCC mapped address */
> @@ -255,8 +265,11 @@ struct sdhci_msm_host {
>  	bool use_cdr;
>  	u32 transfer_mode;
>  	bool updated_ddr_cfg;
> +	struct sdhci_msm_bus_vote_data *bus_vote_data;
>  };
>  
> +static void sdhci_msm_bus_voting(struct sdhci_host *host, u32 enable);
> +
>  static const struct sdhci_msm_offset *sdhci_priv_msm_offset(struct sdhci_host *host)
>  {
>  	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> @@ -1564,6 +1577,7 @@ static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
>  
>  	msm_set_clock_rate_for_bus_mode(host, clock);
>  out:
> +	sdhci_msm_bus_voting(host, !!clock);
>  	__sdhci_msm_set_clock(host, clock);
>  }
>  
> @@ -1685,6 +1699,219 @@ static void sdhci_msm_set_regulator_caps(struct sdhci_msm_host *msm_host)
>  	pr_debug("%s: supported caps: 0x%08x\n", mmc_hostname(mmc), caps);
>  }
>  
> +/*
> + * Returns required bandwidth in Bytes per Sec
> + */
> +static unsigned long sdhci_get_bw_required(struct sdhci_host *host,
> +					struct mmc_ios *ios)
> +{
> +	unsigned long bw;
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> +
> +	bw = msm_host->clk_rate;

nit: you could declare 'bw' last and do the assignment together with the
declaration.

> +
> +	if (ios->bus_width == MMC_BUS_WIDTH_4)
> +		bw /= 2;
> +	else if (ios->bus_width == MMC_BUS_WIDTH_1)
> +		bw /= 8;
> +
> +	return bw;
> +}
> +
> +/*
> + * Helper function to parse the exact OPP node
> + * Returns OPP pointer on success else NULL on error
> + */
> +static struct dev_pm_opp *find_opp_for_freq(struct sdhci_msm_host *msm_host,
> +							unsigned long bw)
> +{
> +	struct dev_pm_opp *opp;
> +	struct sdhci_host *host = mmc_priv(msm_host->mmc);
> +	unsigned int freq = bw;
> +	struct device *dev = &msm_host->pdev->dev;
> +
> +
> +	if (!freq)
> +		opp = dev_pm_opp_find_peak_bw_floor(dev, &freq);
> +	else
> +		opp = dev_pm_opp_find_peak_bw_exact(dev, freq, true);
> +
> +	/* Max Bandwidth vote */

s/Bandwidth/bandwidth/

> +	if (PTR_ERR(opp) == -ERANGE && freq > sdhci_msm_get_max_clock(host))
> +		opp = dev_pm_opp_find_peak_bw_ceil(dev, &bw);
> +
> +	if (IS_ERR(opp)) {
> +		dev_err(dev, "Failed to find OPP for freq:%u err:%ld\n",
> +				freq, PTR_ERR(opp));
> +		return NULL;
> +	}
> +	return opp;
> +}
> +
> +/*
> + * This function sets the interconnect bus bandwidth
> + * vote based on bw (bandwidth) argument.
> + */
> +#define BUS_INTERCONNECT_PATHS 2 /* 1. sdhc -> ddr 2. cpu -> sdhc */
> +static void sdhci_msm_bus_set_vote(struct sdhci_host *host,
> +						unsigned int bw)
> +{
> +	int i;
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> +	struct sdhci_msm_bus_vote_data *vote_data = msm_host->bus_vote_data;
> +	struct dev_pm_opp *opp;
> +	unsigned long freq = bw;
> +	unsigned long ib[BUS_INTERCONNECT_PATHS], ab[BUS_INTERCONNECT_PATHS];

the names are not very expressive, how about peak_bw and avg_bw?

> +	int ddr_rc = 0, cpu_rc = 0;

initialization is not needed

> +
> +	if (!msm_host->bus_vote_data->sdhc_to_ddr ||
> +			!msm_host->bus_vote_data->cpu_to_sdhc)
> +		return;
> +
> +	if (bw != vote_data->curr_freq) {

  	if (bw == vote_data->curr_freq)
		return;


> +		for (i = 0; i < BUS_INTERCONNECT_PATHS; i++) {
> +			opp = find_opp_for_freq(msm_host, freq);
> +			if (opp) {
> +				ab[i] =	dev_pm_opp_get_bw(opp, &ib[i]);
> +				freq += 1; /* Next Band width vote */

s/Band width/bandwidth/

> +				dev_pm_opp_put(opp);
> +			}
> +		}
> +		pr_debug("%s: freq:%d sdhc_to_ddr ab:%lu ib:%lu cpu_to_sdhc ab:%lu ib:%lu\n",
> +				mmc_hostname(host->mmc), bw, ab[0], ib[0],
> +				ab[1], ib[1]);
> +		ddr_rc = icc_set_bw(vote_data->sdhc_to_ddr, 0, ib[0]);
> +		cpu_rc = icc_set_bw(vote_data->cpu_to_sdhc, 0, ib[1]);
> +		if (ddr_rc || cpu_rc) {
> +			pr_err("%s: icc_set() failed ddr_rc_err:%d cpu_rc_err:%d\n",
> +				mmc_hostname(host->mmc), ddr_rc, cpu_rc);
> +			return;
> +		}
> +		vote_data->curr_freq = bw;
> +	}
> +}
> +
> +/*
> + * This function registers the device to OPP framework and
> + * parses few optional parameters from the device tree node.
> + * Returns NULL bvd pointer on error else a valid bvd pointer.
> + */
> +static struct sdhci_msm_bus_vote_data *sdhci_msm_get_bus_vote_data(struct device
> +				       *dev, struct sdhci_msm_host *host)
> +
> +{
> +	struct platform_device *pdev = to_platform_device(dev);
> +	struct sdhci_msm_bus_vote_data *vote_data = NULL;
> +	int ret = 0;

initialization of 'vote_data' and 'ret' is not needed.

> +
> +	if (!pdev) {
> +		dev_err(dev, "Null platform device!\n");
> +		return NULL;
> +	}

It's probably safe to assume that the device is a platform device?

> +	vote_data = devm_kzalloc(dev, sizeof(*vote_data), GFP_KERNEL);
> +	if (!vote_data)
> +		return vote_data;

  		return ERR_PTR(-ENOMEM); ?

> +
> +	ret = dev_pm_opp_of_add_table(dev);
> +	if (ret) {
> +		if (ret == -ENODEV || ret == -ENODATA) {
> +			dev_dbg(dev, "OPP not found. Skip bus voting!!:%d\n",
> +					ret);
> +			vote_data->skip_bus_bw_voting = true;
> +		} else {
> +			dev_dbg(dev, "OPP regestration failed:%d\n", ret);

s/regestration/registration/

Depending on the consequences of this failure (e.g. probe() fails) you
probably want to use dev_warn() or dev_err() here.

> +			goto err;
> +		}
> +	}
> +
> +	return vote_data;
> +err:
> +	devm_kfree(dev, vote_data);
> +	vote_data = NULL;

not needed

> +	return vote_data;

  	return NULL;

> +}
> +
> +/*
> + * Helper function to register for OPP and interconnect
> + * frameworks.
> + */
> +static int sdhci_msm_bus_register(struct sdhci_msm_host *host,
> +				struct platform_device *pdev)
> +{
> +	struct sdhci_msm_bus_vote_data *vote_data;
> +	struct device *dev = &pdev->dev;
> +	int ret = 0;
> +
> +	vote_data = sdhci_msm_get_bus_vote_data(dev, host);
> +	if (!vote_data) {
> +		dev_dbg(&pdev->dev, "Failed to get bus_scale data\n");

In general I'm not convinced about the use of dev_dbg() in the error
paths. Maybe there is some signal you can use to determine if there
should be a valid bus scaling information (e.g. some DT property
exists). If it exists you proceed with obtaining the necessary
information and complain loudly if something goes wrong, otherwise you
don't even try to obtain it and omit the debug logs.

> +		host->bus_vote_data = NULL;

IIUC struct sdhci_msm_host is zero initialized by sdhci_pltfm_init(),
hence the assignment to NULL is not needed.

> +		return -EINVAL;

Use the error returned by sdhci_msm_get_bus_vote_data().

> +	}
> +	host->bus_vote_data = vote_data;
> +
> +	vote_data->sdhc_to_ddr = of_icc_get(&pdev->dev, "sdhc-ddr");

This could be the signal I mentioned above. If this entry does not
exist it is pointless to proceed. You could check this before
sdhci_msm_get_bus_vote_data() and abort with a dev_info() message in
case it doesn't exist. If it exists any error afterwards will be
reported with dev_err().

> +	if (!vote_data->sdhc_to_ddr) {
> +		dev_dbg(&pdev->dev, "DT property for path %s missing\n",
> +				"sdhc-ddr");
> +		return -ENOENT;
> +	} else if (IS_ERR(vote_data->sdhc_to_ddr) {
> +		dev_dbg(&pdev->dev, "(%ld): failed getting %s path\n",
> +				PTR_ERR(vote_data->sdhc_to_ddr), "sdhc-ddr");
> +		ret = PTR_ERR(vote_data->sdhc_to_ddr);
> +		vote_data->sdhc_to_ddr = NULL;
> +		return ret;

if there is an error probe() should probably be aborted. If that's the
case you can replace the above three lines with 'return PTR_ERR(vote_data->sdhc_to_ddr);'

> +	}
> +	vote_data->cpu_to_sdhc = of_icc_get(&pdev->dev, "cpu-sdhc");
> +	if (!vote_data->cpu_to_sdhc) {
> +		dev_dbg(&pdev->dev, "DT property for path %s missing\n",
> +					"cpu_to_sdhc");
> +		return -ENOENT;
> +	} else if (IS_ERR(vote_data->cpu_to_sdhc)) {
> +		dev_dbg(&pdev->dev, "(%ld): failed getting %s path\n",
> +				PTR_ERR(vote_data->cpu_to_sdhc), "cpu-sdhc");
> +		ret = PTR_ERR(vote_data->cpu_to_sdhc);
> +		vote_data->cpu_to_sdhc = NULL;
> +		return ret;

same comment as above

> +	}
> +	return ret;

no error if we get to this point, hence:

	return 0;

> +}
> +
> +static void sdhci_msm_bus_unregister(struct device *dev,
> +				struct sdhci_msm_host *host)
> +{
> +	struct sdhci_msm_bus_vote_data *vote_data = host->bus_vote_data;
> +
> +	if (vote_data->skip_bus_bw_voting ||
> +		!vote_data->sdhc_to_ddr ||
> +		!vote_data->cpu_to_sdhc)
> +		return;
> +
> +	icc_put(vote_data->sdhc_to_ddr);
> +	icc_put(vote_data->cpu_to_sdhc);
> +}
> +
> +#define MSM_MMC_BUS_VOTING_DELAY        200 /* msecs */
> +
> +static void sdhci_msm_bus_voting(struct sdhci_host *host, u32 enable)

s/u32/bool/ ?

> +{
> +	struct mmc_ios *ios = &host->mmc->ios;
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> +	unsigned int bw;
> +
> +	if (msm_host->bus_vote_data->skip_bus_bw_voting)
> +		return;
> +
> +	if (enable) {
> +		bw = sdhci_get_bw_required(host, ios);
> +		sdhci_msm_bus_set_vote(host, bw);
> +	} else
> +		sdhci_msm_bus_set_vote(host, 0);
> +}
> +
>  static const struct sdhci_msm_variant_ops mci_var_ops = {
>  	.msm_readl_relaxed = sdhci_msm_mci_variant_readl_relaxed,
>  	.msm_writel_relaxed = sdhci_msm_mci_variant_writel_relaxed,
> @@ -1845,11 +2072,20 @@ static int sdhci_msm_probe(struct platform_device *pdev)
>  		dev_warn(&pdev->dev, "TCXO clk not present (%d)\n", ret);
>  	}
>  
> +	ret = sdhci_msm_bus_register(msm_host, pdev);
> +	if (ret && msm_host->bus_vote_data &&
> +			!msm_host->bus_vote_data->skip_bus_bw_voting) {
> +		dev_err(&pdev->dev, "Bus registration failed (%d)\n", ret);
> +		goto clk_disable;
> +	}
> +
> +	sdhci_msm_bus_voting(host, 1);

s/1/true/

> +
>  	if (!msm_host->mci_removed) {
>  		msm_host->core_mem = devm_platform_ioremap_resource(pdev, 1);
>  		if (IS_ERR(msm_host->core_mem)) {
>  			ret = PTR_ERR(msm_host->core_mem);
> -			goto clk_disable;
> +			goto bus_unregister;
>  		}
>  	}
>  
> @@ -1924,7 +2160,7 @@ static int sdhci_msm_probe(struct platform_device *pdev)
>  	msm_host->pwr_irq = platform_get_irq_byname(pdev, "pwr_irq");
>  	if (msm_host->pwr_irq < 0) {
>  		ret = msm_host->pwr_irq;
> -		goto clk_disable;
> +		goto bus_unregister;
>  	}
>  
>  	sdhci_msm_init_pwr_irq_wait(msm_host);
> @@ -1937,7 +2173,7 @@ static int sdhci_msm_probe(struct platform_device *pdev)
>  					dev_name(&pdev->dev), host);
>  	if (ret) {
>  		dev_err(&pdev->dev, "Request IRQ failed (%d)\n", ret);
> -		goto clk_disable;
> +		goto bus_unregister;
>  	}
>  
>  	pm_runtime_get_noresume(&pdev->dev);
> @@ -1962,6 +2198,9 @@ static int sdhci_msm_probe(struct platform_device *pdev)
>  	pm_runtime_disable(&pdev->dev);
>  	pm_runtime_set_suspended(&pdev->dev);
>  	pm_runtime_put_noidle(&pdev->dev);
> +bus_unregister:
> +	sdhci_msm_bus_voting(host, 0);

s/0/false/

> +	sdhci_msm_bus_unregister(&pdev->dev, msm_host);
>  clk_disable:
>  	clk_bulk_disable_unprepare(ARRAY_SIZE(msm_host->bulk_clks),
>  				   msm_host->bulk_clks);
> @@ -1991,6 +2230,9 @@ static int sdhci_msm_remove(struct platform_device *pdev)
>  				   msm_host->bulk_clks);
>  	if (!IS_ERR(msm_host->bus_clk))
>  		clk_disable_unprepare(msm_host->bus_clk);
> +
> +	sdhci_msm_bus_voting(host, 0);

s/0/false/

> +	sdhci_msm_bus_unregister(&pdev->dev, msm_host);
>  	sdhci_pltfm_free(pdev);
>  	return 0;
>  }
> @@ -2003,7 +2245,7 @@ static __maybe_unused int sdhci_msm_runtime_suspend(struct device *dev)
>  
>  	clk_bulk_disable_unprepare(ARRAY_SIZE(msm_host->bulk_clks),
>  				   msm_host->bulk_clks);
> -
> +	sdhci_msm_bus_voting(host, 0);

s/0/false/

>  	return 0;
>  }
>  
> @@ -2025,6 +2267,7 @@ static __maybe_unused int sdhci_msm_runtime_resume(struct device *dev)
>  	if (msm_host->restore_dll_config && msm_host->clk_rate)
>  		return sdhci_msm_restore_sdr_dll_config(host);
>  
> +	sdhci_msm_bus_voting(host, 1);

s/0/true/

Thanks

Matthias