Re: [PATCH v2 2/2] mmc: dw_mmc: Add the ability to set the ciu clock frequency

Jaehoon Chung
2013-06-18T04:51:28Z

Hi Doug,

I have one question for using <clock-frequency>.
I found the fixed-rate-clocks feature.
If we want to set <clock-frequency>, then can we use the fixed-rate-clocks?
i'm not sure how use the fixed-rate-clocks. but it seems to set fixed-rate value for clock frequency.

clk_set_rate() didn't ensure to set the <clock-frequency> value.

Best Regards,
Jaehoon Chung

On 06/08/2013 02:28 AM, 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@chromium.org>
> Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
> ---
> Changes in v2:
> - Added example as per Jaehoon.
>
> .../devicetree/bindings/mmc/synopsis-dw-mshc.txt | 16 ++++++++++++++++
> drivers/mmc/host/dw_mmc.c | 17 +++++++++++++----
> 2 files changed, 29 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt b/Documentation/devicetree/bindings/mmc/synopsis-dw-mshc.txt
> index d5cc94e..dd31b00 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
> @@ -70,6 +83,8 @@ board specific portions as listed below.
>
> dwmmc0@12200000 {
> compatible = "snps,dw-mshc";
> + clocks = <&clock 351>, <&clock 132>;
> + clock-names = "biu", "ciu";
> reg = <0x12200000 0x1000>;
> interrupts = <0 75 0>;
> #address-cells = <1>;
> @@ -77,6 +92,7 @@ board specific portions as listed below.
> };
>
> dwmmc0@12200000 {
> + clock-frequency = <400000000>;
> num-slots = <1>;
> supports-highspeed;
> broken-cd;
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index ab5642d..b8a2f16 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -2107,6 +2107,7 @@ 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) {
> @@ -2133,6 +2134,9 @@ 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)
> @@ -2190,18 +2194,23 @@ 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);
>