Re: [PATCH v5 03/12] mmc: sdhci-msm: add pltfm_data support to get clk-rates from DT

[Ritesh Harjani <riteshh@codeaurora.org>]

Hi Rob

On 10/11/2016 12:59 AM, Rob Herring wrote:
> On Mon, Oct 10, 2016 at 11:07 AM, Ritesh Harjani <riteshh@codeaurora.org> wrote:
>> Hi Rob,
>>
>> Thanks for review.
>>
>> On 10/10/2016 6:27 PM, Rob Herring wrote:
>>>
>>> On Wed, Oct 05, 2016 at 08:10:31PM +0530, Ritesh Harjani wrote:
>>>>
>>>> This adds support for sdhc-msm controllers to get supported
>>>> clk-rates from DT. sdhci-msm would need it's own set_clock
>>>> ops to be implemented. For this, supported clk-rates needs
>>>> to be populated in sdhci_msm_pltfm_data.
>>>>
>>>> Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>
>>>> ---
>>>>  .../devicetree/bindings/mmc/sdhci-msm.txt          |  1 +
>>>>  drivers/mmc/host/sdhci-msm.c                       | 48
>>>> ++++++++++++++++++++++
>>>>  2 files changed, 49 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
>>>> b/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
>>>> index 485483a..6a83b38 100644
>>>> --- a/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
>>>> +++ b/Documentation/devicetree/bindings/mmc/sdhci-msm.txt
>>>> @@ -17,6 +17,7 @@ Required properties:
>>>>         "iface" - Main peripheral bus clock (PCLK/HCLK - AHB Bus clock)
>>>> (required)
>>>>         "core"  - SDC MMC clock (MCLK) (required)
>>>>         "bus"   - SDCC bus voter clock (optional)
>>>> +- clk-rates: Array of supported GCC clock frequencies for sdhc, Units -
>>>> Hz.
>>>
>>>
>>> Why can't some combination of assigned-clock-rates and querying the
>>> clock provider for rates be used here?
>>
>> From what I understood, assigned-clock-rates would only work for setting
>> some default clock rates for certain clocks by calling
>> of_clk_set_defaults.
>>
>> Whereas the requirement here is -
>> That since SDHC msm directly controls the clk(core clock) at source, it's
>> sdhci-msm driver needs to know the supported clk-rates by the underlying
>> platform to configure the nearest floor value supported on this platform
>> (when the request arrives from the core layer to switch the clock).
>
> Why does clk_round_rate not work for you? That will round down to the
> nearest frequency supported.
clk_round_rate will round off to nearest supported "ceil" frequency.
But we require nearest rounded off "floor" frequency.

>
>> Hence the table of clk-rates is provided for sdhci-msm.
>>
>>>
>>> Minimally this would need unit suffix and either be made common or have
>>> a vendor prefix.
>>
>> Sure will this work in that case - "qcom-clk-rates"
>
> "qcom,clk-rates", but I'm not yet convinced this is right.
>
> Rob
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