linux-kernel - Re: [PATCH 1/3] dt-bindings: mmc: sdhci-am654: Update Output tap delay binding

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Date:   Fri, 7 Feb 2020 15:07:30 +0530
From:   Faiz Abbas <faiz_abbas@...com>
To:     Rob Herring <robh@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-mmc@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <ulf.hansson@...aro.org>,
        <adrian.hunter@...el.com>
Subject: Re: [PATCH 1/3] dt-bindings: mmc: sdhci-am654: Update Output tap
 delay binding

Rob,

On 20/01/20 11:00 am, Faiz Abbas wrote:
> Hi Rob,
> 
> On 15/01/20 7:20 am, Rob Herring wrote:
>> On Wed, Jan 08, 2020 at 08:39:18PM +0530, Faiz Abbas wrote:
>>> According to latest AM65x Data Manual[1], a different output tap delay
>>> value is recommended for all speed modes. Therefore, replace the
>>> ti,otap-del-sel binding with one ti,otap-del-sel- for each MMC/SD speed
>>> mode.
>>>
>>> [1] http://www.ti.com/lit/gpn/am6526
>>>
>>> Signed-off-by: Faiz Abbas <faiz_abbas@...com>
>>> ---
>>>  .../devicetree/bindings/mmc/sdhci-am654.txt   | 21 +++++++++++++++++--
>>>  1 file changed, 19 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/mmc/sdhci-am654.txt b/Documentation/devicetree/bindings/mmc/sdhci-am654.txt
>>> index 50e87df47971..c6ccecb9ae5a 100644
>>> --- a/Documentation/devicetree/bindings/mmc/sdhci-am654.txt
>>> +++ b/Documentation/devicetree/bindings/mmc/sdhci-am654.txt
>>> @@ -18,7 +18,20 @@ Required Properties:
>>>  	- clocks: Handles to the clock inputs.
>>>  	- clock-names: Tuple including "clk_xin" and "clk_ahb"
>>>  	- interrupts: Interrupt specifiers
>>> -	- ti,otap-del-sel: Output Tap Delay select
>>> +	Output tap delay for each speed mode:
>>> +	- ti,otap-del-sel-legacy
>>> +	- ti,otap-del-sel-mmc-hs
>>> +	- ti,otap-del-sel-sd-hs
>>> +	- ti,otap-del-sel-sdr12
>>> +	- ti,otap-del-sel-sdr25
>>> +	- ti,otap-del-sel-sdr50
>>> +	- ti,otap-del-sel-sdr104
>>> +	- ti,otap-del-sel-ddr50
>>> +	- ti,otap-del-sel-ddr52
>>> +	- ti,otap-del-sel-hs200
>>> +	- ti,otap-del-sel-hs400
>>> +	  These bindings must be provided otherwise the driver will disable the
>>> +	  corresponding speed mode (i.e. all nodes must provide at least -legacy)
>>
>> Why not just extend the existing property to be an array. We already 
>> have properties to enable/disable speed modes.
>>
> 
> Its hard to keep track of which modes have values and which don't when
> you add an array. This scheme is just easier on anyone adding new values
> or updating old values.
> 
> We already disable speed modes based on platform specific properties in
> other drivers. In sdhci-omap.c, the driver disables the corresponding
> speed mode if the corresponding pinmux and iodelay values are not populated.
> 

Do you agree on above?

Thanks,
Faiz