+Jarkko and Andy

On Tue, Dec 15, 2015 at 04:38:58PM -0600, Suravee Suthikulpanit wrote:
> The current driver uses input clock source frequency to calculate
> values for [SS|FS]_[HC|LC] registers. However, when booting ACPI, we do not
> currently have a good way to provide the frequency information.
> Instead, we can leverage the SSCN and FFCN ACPI methods, which can be used
> to directly provide these values.
> 
> So, this patch removes the clock requirement when SSCN and FFCN
> are provided.

Actually I think the only thing you need to change is i2c_dw_init() so
that it does not call dev->get_clk_rate_khz(dev) if *CNT values are
already provided.

The clk framework should work fine if the returned clock is NULL (which
I think is your case).

The driver gates clocks when the device is suspended and on Intel LPSS
there actually is a clock that gets gated.

> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpa...@amd.com>
> ---
> 
> Note: This has been tested on AMD Seattle RevB for both DT and ACPI.
> 
>  drivers/i2c/busses/i2c-designware-core.c    |  5 +++--
>  drivers/i2c/busses/i2c-designware-platdrv.c | 30 
> +++++++++++++++++++++++------
>  2 files changed, 27 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-designware-core.c 
> b/drivers/i2c/busses/i2c-designware-core.c
> index 8c48b27..ec458ec 100644
> --- a/drivers/i2c/busses/i2c-designware-core.c
> +++ b/drivers/i2c/busses/i2c-designware-core.c
> @@ -281,7 +281,7 @@ static void __i2c_dw_enable(struct dw_i2c_dev *dev, bool 
> enable)
>   */
>  int i2c_dw_init(struct dw_i2c_dev *dev)
>  {
> -     u32 input_clock_khz;
> +     u32 input_clock_khz = 0;
>       u32 hcnt, lcnt;
>       u32 reg;
>       u32 sda_falling_time, scl_falling_time;
> @@ -295,7 +295,8 @@ int i2c_dw_init(struct dw_i2c_dev *dev)
>               }
>       }
>  
> -     input_clock_khz = dev->get_clk_rate_khz(dev);
> +     if (dev->get_clk_rate_khz)
> +             input_clock_khz = dev->get_clk_rate_khz(dev);
>  
>       reg = dw_readl(dev, DW_IC_COMP_TYPE);
>       if (reg == ___constant_swab32(DW_IC_COMP_TYPE_VALUE)) {
> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c 
> b/drivers/i2c/busses/i2c-designware-platdrv.c
> index 809579e..57f623b 100644
> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -127,6 +127,26 @@ static inline int dw_i2c_acpi_configure(struct 
> platform_device *pdev)
>  }
>  #endif
>  
> +static int dw_i2c_configure_clk(struct platform_device *pdev,
> +                             struct dw_i2c_dev *dev)
> +{
> +     /* For ACPI, if SSCN and FMCN is provided, we should not
> +      * need the clock value.
> +      */
> +     if (has_acpi_companion(&pdev->dev) &&
> +         dev->ss_hcnt && dev->ss_lcnt &&
> +         dev->fs_hcnt && dev->fs_lcnt)
> +             return 0;
> +
> +     dev->clk = devm_clk_get(&pdev->dev, NULL);
> +     dev->get_clk_rate_khz = i2c_dw_get_clk_rate_khz;
> +     if (IS_ERR(dev->clk))
> +             return PTR_ERR(dev->clk);
> +     clk_prepare_enable(dev->clk);
> +
> +     return 0;
> +}
> +
>  static int dw_i2c_plat_probe(struct platform_device *pdev)
>  {
>       struct dw_i2c_dev *dev;
> @@ -203,13 +223,11 @@ static int dw_i2c_plat_probe(struct platform_device 
> *pdev)
>               dev->master_cfg =  DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
>                       DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
>  
> -     dev->clk = devm_clk_get(&pdev->dev, NULL);
> -     dev->get_clk_rate_khz = i2c_dw_get_clk_rate_khz;
> -     if (IS_ERR(dev->clk))
> -             return PTR_ERR(dev->clk);
> -     clk_prepare_enable(dev->clk);
> +     r = dw_i2c_configure_clk(pdev, dev);
> +     if (r)
> +             return r;
>  
> -     if (!dev->sda_hold_time && ht) {
> +     if (!dev->sda_hold_time && ht && dev->get_clk_rate_khz) {
>               u32 ic_clk = dev->get_clk_rate_khz(dev);
>  
>               dev->sda_hold_time = div_u64((u64)ic_clk * ht + 500000,
> -- 
> 2.5.0
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