[RFC v4 0/2] Add SDHC interconnect bandwidth scaling

[RFC v4 0/2] Add SDHC interconnect bandwidth scaling

[Pradeep P V K]

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
[RFC] mmc: host: sdhci-msm: Use the interconnect API
(https://lkml.org/lkml/2018/10/11/499) and

[PATCH v6] Introduce Bandwidth OPPs for interconnects
(https://lkml.org/lkml/2019/12/6/740)

Pradeep P V K (2):
  mmc: sdhci-msm: Add interconnect bus bandwidth scaling support
  dt-bindings: mmc: sdhci-msm: Add interconnect BW scaling strings

 .../devicetree/bindings/mmc/sdhci-msm.txt          |  18 ++
 drivers/mmc/host/sdhci-msm.c                       | 204 ++++++++++++++++++++-
 2 files changed, 218 insertions(+), 4 deletions(-)

--
changes from RFC v3 -> v4:
- Addressed review comments from Bjorn and Matthias
1.9.1

[RFC v4 1/2] mmc: sdhci-msm: Add interconnect bus bandwidth scaling support

[Pradeep P V K]

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
[RFC] mmc: host: sdhci-msm: Use the interconnect API
(https://lkml.org/lkml/2018/10/11/499) and

[PATCH v6] Introduce Bandwidth OPPs for interconnects
(https://lkml.org/lkml/2019/12/6/740)

Co-developed-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Co-developed-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Co-developed-by: Veerabhadrarao Badiganti <vbadigan@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>
---

changes from RFC v3 -> v4:

- Addressed review comments from Bjorn and Matthias

 drivers/mmc/host/sdhci-msm.c | 204 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 200 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
index 71f29ba..5af1c58 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 +231,12 @@ 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;
+	u32 curr_freq;
+};
+
 struct sdhci_msm_host {
 	struct platform_device *pdev;
 	void __iomem *core_mem;	/* MSM SDCC mapped address */
@@ -255,8 +263,11 @@ 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, bool 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 +1575,7 @@ 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 +1697,174 @@ 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)
+{
+	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
+
+	switch (ios->bus_width) {
+	case MMC_BUS_WIDTH_1:
+		return msm_host->clk_rate/8;
+	case MMC_BUS_WIDTH_4:
+		return msm_host->clk_rate/2;
+	case MMC_BUS_WIDTH_8:
+		break;
+	}
+	return msm_host->clk_rate;
+}
+
+/*
+ * Helper function to parse the exact OPP node
+ * Returns OPP pointer on success else NULL on error
+ */
+static struct dev_pm_opp
+		*sdhci_msm_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 */
+	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, ddr_rc, cpu_rc;
+	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 device *dev = &msm_host->pdev->dev;
+	struct dev_pm_opp *opp;
+	unsigned long freq = bw;
+	unsigned long peak_bw[BUS_INTERCONNECT_PATHS] = {0};
+	unsigned long avg_bw[BUS_INTERCONNECT_PATHS] = {0};
+
+	if (bw == vote_data->curr_freq)
+		return;
+
+	for (i = 0; i < BUS_INTERCONNECT_PATHS; i++) {
+		opp = sdhci_msm_find_opp_for_freq(msm_host, freq);
+		if (opp) {
+			avg_bw[i] = dev_pm_opp_get_bw(opp, &peak_bw[i]);
+			freq += 1; /* Next bandwidth vote */
+			dev_pm_opp_put(opp);
+		}
+	}
+	pr_debug("%s: freq:%d sdhc_to_ddr avg_bw:%lu peak_bw:%lu cpu_to_sdhc avg_bw:%lu peak_bw:%lu\n",
+			mmc_hostname(host->mmc), bw, avg_bw[0], peak_bw[0],
+				avg_bw[1], peak_bw[1]);
+	ddr_rc = icc_set_bw(vote_data->sdhc_to_ddr, 0, peak_bw[0]);
+	cpu_rc = icc_set_bw(vote_data->cpu_to_sdhc, 0, peak_bw[1]);
+	if (ddr_rc || cpu_rc) {
+		dev_err(dev, "icc_set() failed ddr_rc:%d cpu_rc:%d\n",
+							ddr_rc, cpu_rc);
+		return;
+	}
+	vote_data->curr_freq = bw;
+}
+
+/*
+ * Helper function to register for OPP and interconnect
+ * frameworks.
+ */
+static struct sdhci_msm_bus_vote_data
+		*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;
+
+	vote_data = devm_kzalloc(dev, sizeof(*vote_data), GFP_KERNEL);
+	if (!vote_data)
+		return NULL;
+
+	vote_data->sdhc_to_ddr = of_icc_get(&pdev->dev, "sdhc-ddr");
+	vote_data->cpu_to_sdhc = of_icc_get(&pdev->dev, "cpu-sdhc");
+	if (!vote_data->sdhc_to_ddr || !vote_data->cpu_to_sdhc) {
+		dev_info(&pdev->dev, "ICC DT property is missing. skip vote !!\n");
+		return NULL;
+	} else if (IS_ERR(vote_data->sdhc_to_ddr) ||
+			IS_ERR(vote_data->cpu_to_sdhc)) {
+		dev_err(&pdev->dev, "(%ld): failed getting %s path\n",
+				PTR_ERR(vote_data->sdhc_to_ddr), "sdhc-ddr");
+		dev_err(&pdev->dev, "(%ld): failed getting %s path\n",
+				PTR_ERR(vote_data->sdhc_to_ddr), "cpu-sdhc");
+
+		return IS_ERR(vote_data->sdhc_to_ddr) ?
+			ERR_CAST(vote_data->sdhc_to_ddr) :
+			ERR_CAST(vote_data->cpu_to_sdhc);
+	}
+	ret = dev_pm_opp_of_add_table(dev);
+	if (ret) {
+		if (ret == -ENODEV || ret == -ENODATA)
+			dev_err(dev, "OPP dt properties missing:%d\n", ret);
+		else
+			dev_err(dev, "OPP registration failed:%d\n", ret);
+		return ERR_PTR(ret);
+	}
+	return vote_data;
+}
+
+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 ||
+		IS_ERR(vote_data->sdhc_to_ddr) ||
+		IS_ERR(vote_data->cpu_to_sdhc))
+		return;
+
+	icc_put(vote_data->sdhc_to_ddr);
+	icc_put(vote_data->cpu_to_sdhc);
+}
+
+static void sdhci_msm_bus_voting(struct sdhci_host *host, bool enable)
+{
+	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 ||
+		IS_ERR(msm_host->bus_vote_data))
+		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 +2025,20 @@ static int sdhci_msm_probe(struct platform_device *pdev)
 		dev_warn(&pdev->dev, "TCXO clk not present (%d)\n", ret);
 	}
 
+	msm_host->bus_vote_data = sdhci_msm_bus_register(msm_host, pdev);
+	if (IS_ERR(msm_host->bus_vote_data)) {
+		ret = PTR_ERR(msm_host->bus_vote_data);
+		dev_err(&pdev->dev, "Bus registration failed (%d)\n", ret);
+		goto clk_disable;
+	}
+
+	sdhci_msm_bus_voting(host, 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 +2113,7 @@ 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 +2126,7 @@ 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 +2151,9 @@ 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, 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 +2183,9 @@ 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, false);
+	sdhci_msm_bus_unregister(&pdev->dev, msm_host);
 	sdhci_pltfm_free(pdev);
 	return 0;
 }
@@ -2003,7 +2198,7 @@ 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, false);
 	return 0;
 }
 
@@ -2025,6 +2220,7 @@ 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, true);
 	return 0;
 }
 
-- 
1.9.1

Re: [RFC v4 1/2] mmc: sdhci-msm: Add interconnect bus bandwidth scaling support

[Matthias Kaehlcke]

Hi Pradeep,

On Tue, Feb 18, 2020 at 06:30:32PM +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
> [RFC] mmc: host: sdhci-msm: Use the interconnect API
> (https://lkml.org/lkml/2018/10/11/499) and
> 
> [PATCH v6] Introduce Bandwidth OPPs for interconnects
> (https://lkml.org/lkml/2019/12/6/740)
> 
> Co-developed-by: Sahitya Tummala <stummala@codeaurora.org>
> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
> Co-developed-by: Subhash Jadavani <subhashj@codeaurora.org>
> Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
> Co-developed-by: Veerabhadrarao Badiganti <vbadigan@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>
> ---
> 
> changes from RFC v3 -> v4:
> 
> - Addressed review comments from Bjorn and Matthias

This is not helpful, please describe in future versions what those
changes are.

> 
>  drivers/mmc/host/sdhci-msm.c | 204 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 200 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index 71f29ba..5af1c58 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 +231,12 @@ 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;
> +	u32 curr_freq;
> +};
> +
>  struct sdhci_msm_host {
>  	struct platform_device *pdev;
>  	void __iomem *core_mem;	/* MSM SDCC mapped address */
> @@ -255,8 +263,11 @@ 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, bool 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 +1575,7 @@ 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 +1697,174 @@ 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)
> +{
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> +
> +	switch (ios->bus_width) {
> +	case MMC_BUS_WIDTH_1:
> +		return msm_host->clk_rate/8;

nit: it would be more readable with spaces around '/'.

> +	case MMC_BUS_WIDTH_4:
> +		return msm_host->clk_rate/2;
> +	case MMC_BUS_WIDTH_8:
> +		break;
> +	}
> +	return msm_host->clk_rate;
> +}
> +
> +/*
> + * Helper function to parse the exact OPP node
> + * Returns OPP pointer on success else NULL on error
> + */
> +static struct dev_pm_opp
> +		*sdhci_msm_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 */
> +	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, ddr_rc, cpu_rc;
> +	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 device *dev = &msm_host->pdev->dev;
> +	struct dev_pm_opp *opp;
> +	unsigned long freq = bw;
> +	unsigned long peak_bw[BUS_INTERCONNECT_PATHS] = {0};
> +	unsigned long avg_bw[BUS_INTERCONNECT_PATHS] = {0};
> +
> +	if (bw == vote_data->curr_freq)
> +		return;
> +
> +	for (i = 0; i < BUS_INTERCONNECT_PATHS; i++) {
> +		opp = sdhci_msm_find_opp_for_freq(msm_host, freq);
> +		if (opp) {
> +			avg_bw[i] = dev_pm_opp_get_bw(opp, &peak_bw[i]);
> +			freq += 1; /* Next bandwidth vote */
> +			dev_pm_opp_put(opp);
> +		}
> +	}
> +	pr_debug("%s: freq:%d sdhc_to_ddr avg_bw:%lu peak_bw:%lu cpu_to_sdhc avg_bw:%lu peak_bw:%lu\n",
> +			mmc_hostname(host->mmc), bw, avg_bw[0], peak_bw[0],
> +				avg_bw[1], peak_bw[1]);
> +	ddr_rc = icc_set_bw(vote_data->sdhc_to_ddr, 0, peak_bw[0]);
> +	cpu_rc = icc_set_bw(vote_data->cpu_to_sdhc, 0, peak_bw[1]);
> +	if (ddr_rc || cpu_rc) {
> +		dev_err(dev, "icc_set() failed ddr_rc:%d cpu_rc:%d\n",
> +							ddr_rc, cpu_rc);
> +		return;
> +	}

Do you necessarily want to set the bandwidth of the CPU to SDHC path, if
setting the bandwidth for the SDHC to DDR path failed? If not I'd suggest
to get rid of this double error handling with 'ddr_rc' and 'cpu_rc' and
handle each error individually.

> +	vote_data->curr_freq = bw;
> +}
> +
> +/*
> + * Helper function to register for OPP and interconnect
> + * frameworks.
> + */
> +static struct sdhci_msm_bus_vote_data
> +		*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;
> +
> +	vote_data = devm_kzalloc(dev, sizeof(*vote_data), GFP_KERNEL);
> +	if (!vote_data)
> +		return NULL;

Even though the interconnects are optional I think we want to propagate an
out of memory error, i.e. you probably want to return -ENOMEM here.

Also the allocated 'vote_data' will not be used if the ICC configuration
does not exist or is invalid. I think Bjorn suggested to do the allocation
after getting the ICC paths and error handling, when you know the struct
is actually used.

> +
> +	vote_data->sdhc_to_ddr = of_icc_get(&pdev->dev, "sdhc-ddr");
> +	vote_data->cpu_to_sdhc = of_icc_get(&pdev->dev, "cpu-sdhc");
> +	if (!vote_data->sdhc_to_ddr || !vote_data->cpu_to_sdhc) {
> +		dev_info(&pdev->dev, "ICC DT property is missing. skip vote !!\n");
> +		return NULL;

This combined handling masks possible misconfigurations/errors, where one
ICC path is specified (correctly or not), and the other not. Also the log
message would be confusing in this case, since the ICC property exists.

Preferably NULL would only be returned if neither of the ICC paths is
specified. The message could be something like "no interconnect configuration".
This is still not entirely correct, since there could be a configuration, just
not with the expected interconnect names.

> +	} else if (IS_ERR(vote_data->sdhc_to_ddr) ||
> +			IS_ERR(vote_data->cpu_to_sdhc)) {
> +		dev_err(&pdev->dev, "(%ld): failed getting %s path\n",
> +				PTR_ERR(vote_data->sdhc_to_ddr), "sdhc-ddr");

What is the point of using '%s' here?

> +		dev_err(&pdev->dev, "(%ld): failed getting %s path\n",
> +				PTR_ERR(vote_data->sdhc_to_ddr), "cpu-sdhc");

ditto

> +
> +		return IS_ERR(vote_data->sdhc_to_ddr) ?
> +			ERR_CAST(vote_data->sdhc_to_ddr) :
> +			ERR_CAST(vote_data->cpu_to_sdhc);
> +	}

The above could print an error message for an ICC path that doesn't
have a problem. Also we don't want to yell in case of deferred probing.

Something like this could be a possible alternative:

     	struct icc_path *icc_paths[BUS_INTERCONNECT_PATHS];
	const char *path_names[] = {
		"sdhc-ddr",
		"cpu-sdhc"
	};

	// use loop?
	icc_paths[0] = of_icc_get(&pdev->dev, "sdhc-ddr");
	icc_paths[1] = of_icc_get(&pdev->dev, "cpu-sdhc");

	if (!icc_paths[0] && !icc_paths[1]) {
		dev_info(...);
		return NULL;
	}

	for (i = 0; i <  BUS_INTERCONNECT_PATHS; i++) {
	       	int err = 0;

		if (!icc_paths[i]) {
			dev_err(pdev->dev. "interconnect path '%s' is not configured\n", path_names[i]);
			err = -EINVAL;
			goto handle_err;
		}

		if (IS_ERR(icc_paths[i]) {
			err = PTR_ERR(icc_paths[i]);

			if (err != -EPROBE_DEFER)
				dev_err(pdev->dev. "interconnect path '%s' is invalid: %d\n", path_names[i], err);
		}

handle_err:
		if (err) {
			int other = (i == 0)? 1 : 0;

			if (!IS_ERR_OR_NULL(icc_paths[other]))
				icc_put(icc_paths[other]);

			return err;
		}
	}

> +	ret = dev_pm_opp_of_add_table(dev);
> +	if (ret) {
> +		if (ret == -ENODEV || ret == -ENODATA)
> +			dev_err(dev, "OPP dt properties missing:%d\n", ret);
> +		else
> +			dev_err(dev, "OPP registration failed:%d\n", ret);
> +		return ERR_PTR(ret);
> +	}

Now that we know that there are no errors we can allocate 'vote_data' and
initialize it.

> +	return vote_data;
> +}
> +
> +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 ||
> +		IS_ERR(vote_data->sdhc_to_ddr) ||
> +		IS_ERR(vote_data->cpu_to_sdhc))

The check for errors in the ICC paths is not necessary. When an error is
encountered sdhci_msm_bus_register() returns an error, not a struct.

> +		return;
> +
> +	icc_put(vote_data->sdhc_to_ddr);
> +	icc_put(vote_data->cpu_to_sdhc);
> +}
> +
> +static void sdhci_msm_bus_voting(struct sdhci_host *host, bool enable)
> +{
> +	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 ||
> +		IS_ERR(msm_host->bus_vote_data))

no need to check for errors, _probe() is aborted in case of errors.

Thanks

Matthias

Re: [RFC v4 1/2] mmc: sdhci-msm: Add interconnect bus bandwidth scaling support

[ppvk]

Thanks Matthias for review and suggestions.

On 2020-02-19 03:51, Matthias Kaehlcke wrote:
> Hi Pradeep,
> 
> On Tue, Feb 18, 2020 at 06:30:32PM +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
>> [RFC] mmc: host: sdhci-msm: Use the interconnect API
>> (https://lkml.org/lkml/2018/10/11/499) and
>> 
>> [PATCH v6] Introduce Bandwidth OPPs for interconnects
>> (https://lkml.org/lkml/2019/12/6/740)
>> 
>> Co-developed-by: Sahitya Tummala <stummala@codeaurora.org>
>> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
>> Co-developed-by: Subhash Jadavani <subhashj@codeaurora.org>
>> Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
>> Co-developed-by: Veerabhadrarao Badiganti <vbadigan@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>
>> ---
>> 
>> changes from RFC v3 -> v4:
>> 
>> - Addressed review comments from Bjorn and Matthias
> 
> This is not helpful, please describe in future versions what those
> changes are.
> 
sure will do this from next patch series.
>> 
>>  drivers/mmc/host/sdhci-msm.c | 204 
>> ++++++++++++++++++++++++++++++++++++++++++-
>>  1 file changed, 200 insertions(+), 4 deletions(-)
>> 
>> diff --git a/drivers/mmc/host/sdhci-msm.c 
>> b/drivers/mmc/host/sdhci-msm.c
>> index 71f29ba..5af1c58 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 +231,12 @@ 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;
>> +	u32 curr_freq;
>> +};
>> +
>>  struct sdhci_msm_host {
>>  	struct platform_device *pdev;
>>  	void __iomem *core_mem;	/* MSM SDCC mapped address */
>> @@ -255,8 +263,11 @@ 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, bool 
>> 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 +1575,7 @@ 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 +1697,174 @@ 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)
>> +{
>> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>> +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
>> +
>> +	switch (ios->bus_width) {
>> +	case MMC_BUS_WIDTH_1:
>> +		return msm_host->clk_rate/8;
> 
> nit: it would be more readable with spaces around '/'.
> 
ok. i will address this in my next patchset.

>> +	case MMC_BUS_WIDTH_4:
>> +		return msm_host->clk_rate/2;
>> +	case MMC_BUS_WIDTH_8:
>> +		break;
>> +	}
>> +	return msm_host->clk_rate;
>> +}
>> +
>> +/*
>> + * Helper function to parse the exact OPP node
>> + * Returns OPP pointer on success else NULL on error
>> + */
>> +static struct dev_pm_opp
>> +		*sdhci_msm_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 */
>> +	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, ddr_rc, cpu_rc;
>> +	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 device *dev = &msm_host->pdev->dev;
>> +	struct dev_pm_opp *opp;
>> +	unsigned long freq = bw;
>> +	unsigned long peak_bw[BUS_INTERCONNECT_PATHS] = {0};
>> +	unsigned long avg_bw[BUS_INTERCONNECT_PATHS] = {0};
>> +
>> +	if (bw == vote_data->curr_freq)
>> +		return;
>> +
>> +	for (i = 0; i < BUS_INTERCONNECT_PATHS; i++) {
>> +		opp = sdhci_msm_find_opp_for_freq(msm_host, freq);
>> +		if (opp) {
>> +			avg_bw[i] = dev_pm_opp_get_bw(opp, &peak_bw[i]);
>> +			freq += 1; /* Next bandwidth vote */
>> +			dev_pm_opp_put(opp);
>> +		}
>> +	}
>> +	pr_debug("%s: freq:%d sdhc_to_ddr avg_bw:%lu peak_bw:%lu cpu_to_sdhc 
>> avg_bw:%lu peak_bw:%lu\n",
>> +			mmc_hostname(host->mmc), bw, avg_bw[0], peak_bw[0],
>> +				avg_bw[1], peak_bw[1]);
>> +	ddr_rc = icc_set_bw(vote_data->sdhc_to_ddr, 0, peak_bw[0]);
>> +	cpu_rc = icc_set_bw(vote_data->cpu_to_sdhc, 0, peak_bw[1]);
>> +	if (ddr_rc || cpu_rc) {
>> +		dev_err(dev, "icc_set() failed ddr_rc:%d cpu_rc:%d\n",
>> +							ddr_rc, cpu_rc);
>> +		return;
>> +	}
> 
> Do you necessarily want to set the bandwidth of the CPU to SDHC path, 
> if
> setting the bandwidth for the SDHC to DDR path failed? If not I'd 
> suggest
> to get rid of this double error handling with 'ddr_rc' and 'cpu_rc' and
> handle each error individually.
> 
It is not required to set bw for CPU to SDHC path, if setting to SDHC to 
DDR path
failed. i will handle this individually in my next patch series.

>> +	vote_data->curr_freq = bw;
>> +}
>> +
>> +/*
>> + * Helper function to register for OPP and interconnect
>> + * frameworks.
>> + */
>> +static struct sdhci_msm_bus_vote_data
>> +		*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;
>> +
>> +	vote_data = devm_kzalloc(dev, sizeof(*vote_data), GFP_KERNEL);
>> +	if (!vote_data)
>> +		return NULL;
> 
> Even though the interconnects are optional I think we want to propagate 
> an
> out of memory error, i.e. you probably want to return -ENOMEM here.
> 
> Also the allocated 'vote_data' will not be used if the ICC 
> configuration
> does not exist or is invalid. I think Bjorn suggested to do the 
> allocation
> after getting the ICC paths and error handling, when you know the 
> struct
> is actually used.
> 
ok i will do this in my next patch set.
>> +
>> +	vote_data->sdhc_to_ddr = of_icc_get(&pdev->dev, "sdhc-ddr");
>> +	vote_data->cpu_to_sdhc = of_icc_get(&pdev->dev, "cpu-sdhc");
>> +	if (!vote_data->sdhc_to_ddr || !vote_data->cpu_to_sdhc) {
>> +		dev_info(&pdev->dev, "ICC DT property is missing. skip vote !!\n");
>> +		return NULL;
> 
> This combined handling masks possible misconfigurations/errors, where 
> one
> ICC path is specified (correctly or not), and the other not. Also the 
> log
> message would be confusing in this case, since the ICC property exists.
> 
> Preferably NULL would only be returned if neither of the ICC paths is
> specified. The message could be something like "no interconnect 
> configuration".
> This is still not entirely correct, since there could be a 
> configuration, just
> not with the expected interconnect names.
> 
i will take care this in my next patch series.

>> +	} else if (IS_ERR(vote_data->sdhc_to_ddr) ||
>> +			IS_ERR(vote_data->cpu_to_sdhc)) {
>> +		dev_err(&pdev->dev, "(%ld): failed getting %s path\n",
>> +				PTR_ERR(vote_data->sdhc_to_ddr), "sdhc-ddr");
> 
> What is the point of using '%s' here?
> 
Not required specifically. i will take care this too in my next patch 
set.

>> +		dev_err(&pdev->dev, "(%ld): failed getting %s path\n",
>> +				PTR_ERR(vote_data->sdhc_to_ddr), "cpu-sdhc");
> 
> ditto
> 
ok.
>> +
>> +		return IS_ERR(vote_data->sdhc_to_ddr) ?
>> +			ERR_CAST(vote_data->sdhc_to_ddr) :
>> +			ERR_CAST(vote_data->cpu_to_sdhc);
>> +	}
> 
> The above could print an error message for an ICC path that doesn't
> have a problem. Also we don't want to yell in case of deferred probing.
> 
> Something like this could be a possible alternative:
> 
>      	struct icc_path *icc_paths[BUS_INTERCONNECT_PATHS];
> 	const char *path_names[] = {
> 		"sdhc-ddr",
> 		"cpu-sdhc"
> 	};
> 
> 	// use loop?
> 	icc_paths[0] = of_icc_get(&pdev->dev, "sdhc-ddr");
> 	icc_paths[1] = of_icc_get(&pdev->dev, "cpu-sdhc");
> 
> 	if (!icc_paths[0] && !icc_paths[1]) {
> 		dev_info(...);
> 		return NULL;
> 	}
> 
> 	for (i = 0; i <  BUS_INTERCONNECT_PATHS; i++) {
> 	       	int err = 0;
> 
> 		if (!icc_paths[i]) {
> 			dev_err(pdev->dev. "interconnect path '%s' is not configured\n",
> path_names[i]);
> 			err = -EINVAL;
> 			goto handle_err;
> 		}
> 
> 		if (IS_ERR(icc_paths[i]) {
> 			err = PTR_ERR(icc_paths[i]);
> 
> 			if (err != -EPROBE_DEFER)
> 				dev_err(pdev->dev. "interconnect path '%s' is invalid: %d\n",
> path_names[i], err);
> 		}
> 
> handle_err:
> 		if (err) {
> 			int other = (i == 0)? 1 : 0;
> 
> 			if (!IS_ERR_OR_NULL(icc_paths[other]))
> 				icc_put(icc_paths[other]);
> 
> 			return err;
> 		}
> 	}
> 
Thanks for the alternate code. i will address this in my next patch set.

>> +	ret = dev_pm_opp_of_add_table(dev);
>> +	if (ret) {
>> +		if (ret == -ENODEV || ret == -ENODATA)
>> +			dev_err(dev, "OPP dt properties missing:%d\n", ret);
>> +		else
>> +			dev_err(dev, "OPP registration failed:%d\n", ret);
>> +		return ERR_PTR(ret);
>> +	}
> 
> Now that we know that there are no errors we can allocate 'vote_data' 
> and
> initialize it.
> 
ok.

>> +	return vote_data;
>> +}
>> +
>> +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 ||
>> +		IS_ERR(vote_data->sdhc_to_ddr) ||
>> +		IS_ERR(vote_data->cpu_to_sdhc))
> 
> The check for errors in the ICC paths is not necessary. When an error 
> is
> encountered sdhci_msm_bus_register() returns an error, not a struct.
> 
ok. i will address this in my next patch set.

>> +		return;
>> +
>> +	icc_put(vote_data->sdhc_to_ddr);
>> +	icc_put(vote_data->cpu_to_sdhc);
>> +}
>> +
>> +static void sdhci_msm_bus_voting(struct sdhci_host *host, bool 
>> enable)
>> +{
>> +	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 ||
>> +		IS_ERR(msm_host->bus_vote_data))
> 
> no need to check for errors, _probe() is aborted in case of errors.
> 
ok.

> Thanks
> 
> Matthias

[RFC v4 2/2] dt-bindings: mmc: sdhci-msm: Add interconnect BW scaling strings

[Pradeep P V K]

Add interconnect bandwidth scaling supported strings for qcom-sdhci
controller.

Signed-off-by: Pradeep P V K <ppvk@codeaurora.org>
---

changes from RFC v3 -> v4:
- No changes.

 Documentation/devicetree/bindings/mmc/sdhci-msm.txt | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/Documentation/devicetree/bindings/mmc/sdhci-msm.txt b/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
index 7ee639b..cbe97b8 100644
--- a/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
+++ b/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
@@ -40,6 +40,21 @@ Required properties:
 	"cal"	- reference clock for RCLK delay calibration (optional)
 	"sleep"	- sleep clock for RCLK delay calibration (optional)
 
+Optional Properties:
+* Following bus parameters are required for interconnect bandwidth scaling:
+- interconnects: Pairs of phandles and interconnect provider specifier
+		 to denote the edge source and destination ports of
+		 the interconnect path.
+
+- interconnect-names: For sdhc, we have two main paths.
+		1. Data path : sdhc to ddr
+		2. Config path : cpu to sdhc
+		For Data interconnect path the name supposed to be
+		is "sdhc-ddr" and for config interconnect path it is
+		"cpu-sdhc".
+		Please refer to Documentation/devicetree/bindings/
+		interconnect/ for more details.
+
 Example:
 
 	sdhc_1: sdhci@f9824900 {
@@ -57,6 +72,9 @@ Example:
 
 		clocks = <&gcc GCC_SDCC1_APPS_CLK>, <&gcc GCC_SDCC1_AHB_CLK>;
 		clock-names = "core", "iface";
+		interconnects = <&qnoc MASTER_SDCC_ID &qnoc SLAVE_DDR_ID>,
+				<&qnoc MASTER_CPU_ID &qnoc SLAVE_SDCC_ID>;
+		interconnect-names = "sdhc-ddr","cpu-sdhc";
 	};
 
 	sdhc_2: sdhci@f98a4900 {
-- 
1.9.1

Re: [RFC v4 2/2] dt-bindings: mmc: sdhci-msm: Add interconnect BW scaling strings

[Rob Herring]

On Tue, 18 Feb 2020 18:30:33 +0530, Pradeep P V K wrote:
> Add interconnect bandwidth scaling supported strings for qcom-sdhci
> controller.
> 
> Signed-off-by: Pradeep P V K <ppvk@codeaurora.org>
> ---
> 
> changes from RFC v3 -> v4:
> - No changes.
> 
>  Documentation/devicetree/bindings/mmc/sdhci-msm.txt | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 

Acked-by: Rob Herring <robh@kernel.org>

Re: [RFC v4 2/2] dt-bindings: mmc: sdhci-msm: Add interconnect BW scaling strings

[Bjorn Andersson]

On Tue 18 Feb 05:00 PST 2020, Pradeep P V K wrote:

> Add interconnect bandwidth scaling supported strings for qcom-sdhci
> controller.
> 
> Signed-off-by: Pradeep P V K <ppvk@codeaurora.org>

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>

> ---
> 
> changes from RFC v3 -> v4:
> - No changes.
> 
>  Documentation/devicetree/bindings/mmc/sdhci-msm.txt | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mmc/sdhci-msm.txt b/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
> index 7ee639b..cbe97b8 100644
> --- a/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
> +++ b/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
> @@ -40,6 +40,21 @@ Required properties:
>  	"cal"	- reference clock for RCLK delay calibration (optional)
>  	"sleep"	- sleep clock for RCLK delay calibration (optional)
>  
> +Optional Properties:
> +* Following bus parameters are required for interconnect bandwidth scaling:
> +- interconnects: Pairs of phandles and interconnect provider specifier
> +		 to denote the edge source and destination ports of
> +		 the interconnect path.
> +
> +- interconnect-names: For sdhc, we have two main paths.
> +		1. Data path : sdhc to ddr
> +		2. Config path : cpu to sdhc
> +		For Data interconnect path the name supposed to be
> +		is "sdhc-ddr" and for config interconnect path it is
> +		"cpu-sdhc".
> +		Please refer to Documentation/devicetree/bindings/
> +		interconnect/ for more details.
> +
>  Example:
>  
>  	sdhc_1: sdhci@f9824900 {
> @@ -57,6 +72,9 @@ Example:
>  
>  		clocks = <&gcc GCC_SDCC1_APPS_CLK>, <&gcc GCC_SDCC1_AHB_CLK>;
>  		clock-names = "core", "iface";
> +		interconnects = <&qnoc MASTER_SDCC_ID &qnoc SLAVE_DDR_ID>,
> +				<&qnoc MASTER_CPU_ID &qnoc SLAVE_SDCC_ID>;
> +		interconnect-names = "sdhc-ddr","cpu-sdhc";
>  	};
>  
>  	sdhc_2: sdhci@f98a4900 {
> -- 
> 1.9.1
>