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SubjectRe: [PATCH v2] i2c: designware: Do not require clock when SSCN and FFCN are provided
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Hi Mika,

On 12/18/2015 4:13 AM, Mika Westerberg wrote:
> [....]
> So instead of this, what if we do not assign dev->get_clk_rate_khz at
> all and then do something like below in the core driver?

I like the changes below since it is clear to see within the core file
how things are handled when get_clk_rate_khz is not assigned (i.e.
input_clock_hz = 0), and not necessary relying on the platform driver to
return 0 in this case.

So, at this point, I can re-submit the V3 and combine these changes, and
we both can sign-off. How does that sound?

Thanks,
Suravee

> Of course we still need the other changes you did in this patch to cope
> with the missing clock.
>
> diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
> index 8c48b27ba059..25dccd8df772 100644
> --- a/drivers/i2c/busses/i2c-designware-core.c
> +++ b/drivers/i2c/busses/i2c-designware-core.c
> @@ -271,6 +271,17 @@ static void __i2c_dw_enable(struct dw_i2c_dev *dev, bool enable)
> enable ? "en" : "dis");
> }
>
> +static unsigned long i2c_dw_clk_rate(struct dw_i2c_dev *dev)
> +{
> + /*
> + * Clock is not necessary if we got LCNT/HCNT values directly from
> + * the platform code.
> + */
> + if (WARN_ON_ONCE(!dev->get_clk_rate_khz))
> + return 0;
> + return dev->get_clk_rate_khz(dev);
> +}
> +
> /**
> * i2c_dw_init() - initialize the designware i2c master hardware
> * @dev: device private data
> @@ -281,7 +292,6 @@ 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 hcnt, lcnt;
> u32 reg;
> u32 sda_falling_time, scl_falling_time;
> @@ -295,8 +305,6 @@ int i2c_dw_init(struct dw_i2c_dev *dev)
> }
> }
>
> - 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)) {
> /* Configure register endianess access */
> @@ -325,12 +333,12 @@ int i2c_dw_init(struct dw_i2c_dev *dev)
> hcnt = dev->ss_hcnt;
> lcnt = dev->ss_lcnt;
> } else {
> - hcnt = i2c_dw_scl_hcnt(input_clock_khz,
> + hcnt = i2c_dw_scl_hcnt(i2c_dw_clk_rate(dev),
> 4000, /* tHD;STA = tHIGH = 4.0 us */
> sda_falling_time,
> 0, /* 0: DW default, 1: Ideal */
> 0); /* No offset */
> - lcnt = i2c_dw_scl_lcnt(input_clock_khz,
> + lcnt = i2c_dw_scl_lcnt(i2c_dw_clk_rate(dev),
> 4700, /* tLOW = 4.7 us */
> scl_falling_time,
> 0); /* No offset */
> @@ -344,12 +352,12 @@ int i2c_dw_init(struct dw_i2c_dev *dev)
> hcnt = dev->fs_hcnt;
> lcnt = dev->fs_lcnt;
> } else {
> - hcnt = i2c_dw_scl_hcnt(input_clock_khz,
> + hcnt = i2c_dw_scl_hcnt(i2c_dw_clk_rate(dev),
> 600, /* tHD;STA = tHIGH = 0.6 us */
> sda_falling_time,
> 0, /* 0: DW default, 1: Ideal */
> 0); /* No offset */
> - lcnt = i2c_dw_scl_lcnt(input_clock_khz,
> + lcnt = i2c_dw_scl_lcnt(i2c_dw_clk_rate(dev),
> 1300, /* tLOW = 1.3 us */
> scl_falling_time,
> 0); /* No offset */
>



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