linux-kernel - Re: [PATCH 2/2] mmc: dw_mmc: Add the ability to set the ciu clock frequency

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Message-id: <51B1712C.5030705@samsung.com>
Date:	Fri, 07 Jun 2013 14:35:40 +0900
From:	Jaehoon Chung <jh80.chung@...sung.com>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Chris Ball <cjb@...top.org>, Olof Johansson <olof@...om.net>,
	Andrew Bresticker <abrestic@...omium.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Abhilash Kesavan <a.kesavan@...sung.com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>,
	Will Newton <will.newton@...tec.com>,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org
Subject: Re: [PATCH 2/2] mmc: dw_mmc: Add the ability to set the ciu clock
 frequency

Looks good to me. If you can add the usage example, it will be more helpful to me.

Acked-by: Jaehoon Chung <jh80.chung@...sung.com>

On 06/07/2013 01:46 PM, Doug Anderson wrote:
> As of now we rely on code outside of the driver to set the ciu clock
> frequency.  There's no reason to do that.  Add support for setting up
> the clock in the driver during probe.
> 
> Signed-off-by: Doug Anderson <dianders@...omium.org>
> ---
>  .../devicetree/bindings/mmc/synopsis-dw-mshc.txt        | 13 +++++++++++++
>  drivers/mmc/host/dw_mmc.c                               | 17 +++++++++++++----
>  2 files changed, 26 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt b/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
> index b09d2d0..edb7659 100644
> --- a/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
> +++ b/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
> @@ -39,6 +39,19 @@ Required Properties:
>  
>  Optional properties:
>  
> +* clocks: from common clock binding: handle to biu and ciu clocks for the
> +  bus interface unit clock and the card interface unit clock.
> +
> +* clock-names: from common clock binding: Shall be "biu" and "ciu".
> +  If the biu clock is missing we'll simply skip enabling it.  If the
> +  ciu clock is missing we'll just assume that the clock is running at
> +  clock-frequency.  It is an error to omit both the ciu clock and the
> +  clock-frequency.
> +
> +* clock-frequency: should be the frequency (in Hz) of the ciu clock.  If this
> +  is specified and the ciu clock is specified then we'll try to set the ciu
> +  clock to this at probe time.
> +
>  * num-slots: specifies the number of slots supported by the controller.
>    The number of physical slots actually used could be equal or less than the
>    value specified by num-slots. If this property is not specified, the value
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index d3a0f8a..7ffb502 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -2133,6 +2133,7 @@ static struct dw_mci_board *dw_mci_parse_dt(struct dw_mci *host)
>  	struct device_node *np = dev->of_node;
>  	const struct dw_mci_drv_data *drv_data = host->drv_data;
>  	int idx, ret;
> +	u32 clock_frequency;
>  
>  	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
>  	if (!pdata) {
> @@ -2159,6 +2160,9 @@ static struct dw_mci_board *dw_mci_parse_dt(struct dw_mci *host)
>  
>  	of_property_read_u32(np, "card-detect-delay", &pdata->detect_delay_ms);
>  
> +	if (!of_property_read_u32(np, "clock-frequency", &clock_frequency))
> +		pdata->bus_hz = clock_frequency;
> +
>  	if (drv_data && drv_data->parse_dt) {
>  		ret = drv_data->parse_dt(host);
>  		if (ret)
> @@ -2223,18 +2227,23 @@ int dw_mci_probe(struct dw_mci *host)
>  	host->ciu_clk = devm_clk_get(host->dev, "ciu");
>  	if (IS_ERR(host->ciu_clk)) {
>  		dev_dbg(host->dev, "ciu clock not available\n");
> +		host->bus_hz = host->pdata->bus_hz;
>  	} else {
>  		ret = clk_prepare_enable(host->ciu_clk);
>  		if (ret) {
>  			dev_err(host->dev, "failed to enable ciu clock\n");
>  			goto err_clk_biu;
>  		}
> -	}
>  
> -	if (IS_ERR(host->ciu_clk))
> -		host->bus_hz = host->pdata->bus_hz;
> -	else
> +		if (host->pdata->bus_hz) {
> +			ret = clk_set_rate(host->ciu_clk, host->pdata->bus_hz);
> +			if (ret)
> +				dev_warn(host->dev,
> +					 "Unable to set bus rate to %ul\n",
> +					 host->pdata->bus_hz);
> +		}
>  		host->bus_hz = clk_get_rate(host->ciu_clk);
> +	}
>  
>  	if (drv_data && drv_data->setup_clock) {
>  		ret = drv_data->setup_clock(host);
> 

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