Hi Leela,
Thanks for the detailed explanation.
On 12 November 2013 17:20, Leela Krishna Amudala
<leelakrishna.a@xxxxxxxxx> wrote:
> Hi Sachin,
>
> On Tue, Nov 12, 2013 at 3:53 PM, Kukjin Kim <kgene@xxxxxxxxxx> wrote:
>> Sachin Kamat wrote:
>>>
>>
>> Following is more clear?
>>
>> "ARM: dts: Add missing GPIO entries for sd_bus_width4 in exynos5420-pinctrl"
>>
>>> Adds missing GPIO entries for sd_bus nodes in exynos5420-pinctrl.
>>>
>
> This is not a missing stuff, I did this purposefully.
> Myself and Doug anderson discussed on this and the objective of doing this is to
> eliminate the gpio pin configuration multiple times.
>
> Please see the below explanation
>
> The current code in main line kernel shows like
> sd0_bus1: sd0-bus-width1 {
> samsung,pins = "gpc0-3";
> };
>
> sd0_bus4: sd0-bus-width4 {
> samsung,pins = "gpc0-4", "gpc0-5", "gpc0-6";
> };
>
> sd0_bus8: sd0-bus-width8 {
> samsung,pins = "gpc3-0", "gpc3-1", "gpc3-2", "gpc3-3";
> };
>
> and lets mmc wants to use 8 bit width then node should be like below
>
> dwmmc0@12200000 {
> [snip]
> pinctrl-names = "default";
> pinctrl-0 = <&sd0_clk &sd0_cmd &sd0_bus1 &sd0_bus4 &sd0_bus8>;
>
> Here it will configure all the 8 pins ("gpc0-3", "gpc0-4", "gpc0-5",
> "gpc0-6", "gpc3-0", "gpc3-1", "gpc3-2", "gpc3-3")
>
> slot@0 {
> reg = <0>;
> bus-width = <8>;
> };
> };
>
> Similarly for using 1 bit width the property value should be like below
> pinctrl-0 = <&sd0_clk &sd0_cmd &sd0_bus1>;
>
> and if other mmc wants to use 4 bit width the property value should be
> like below
> pinctrl-0 = <&sd0_clk &sd0_cmd &sd0_bus1 &sd0_bus4>;
>
> But with the changes you made and if one mmc wants to use 1 bit width
> and other wants to use 4 bit width
> the pin "gpc0-3" will be configured twice which is wrong.
I think this is the case with current code too.
>From your above example, for 2 slots:
For 1 bit width: pinctrl-0 = <&sd0_clk &sd0_cmd &sd0_bus1>;
"gpc0-3"
For 4 bit width: pinctrl-0 = <&sd0_clk &sd0_cmd &sd0_bus1 &sd0_bus4>;
"gpc0-3", "gpc0-4", "gpc0-5", "gpc0-6"
> So, I strongly feel it is better to change the existing mmc node
> instead of changing the "sd0_bus" entries
I think this is already taken care of in the mmc nodes.
For slot with bus-width of 8,
pinctrl-0 = <&sd0_clk &sd0_cmd &sd0_bus4 &sd0_bus8>;
Similarly for slot with bus width of 4,
pinctrl-0 = <&sd2_clk &sd2_cmd &sd2_cd &sd2_bus4>;
Do you still see the problem here?
--
With warm regards,
Sachin
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