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

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Date:   Mon, 20 Jan 2020 11:00:46 +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

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.

Thanks,
Faiz

Thanks,
Faiz