[v6,2/3] mmc: sh_mobile_sdhi: explain clock bindings

Commit Message

Chris Brandt Jan. 25, 2017, 8:28 p.m. UTC

In the case of a single clock source, you don't need names. However,
if the controller has 2 clock sources, you need to name them correctly
so the driver can find the 2nd one. The 2nd clock is for the internal
card detect logic.

Signed-off-by: Chris Brandt <[e-mail]>
Reviewed-by: Geert Uytterhoeven <[e-mail]>
---
v5:
* add Reviewed-by: Geert Uytterhoeven
* list number of clocks for each SoC
* remove example because it already exists in mmc.txt
v4:
* just explain there might be 2 clocks, don't explain how
  we will use them in the driver
v3:
* add more clarification about why there are sometimes 2 clocks
  and what you should do with them.
* remove 'status = "disabled"' from example
v2:
* fix spelling and change wording
* changed clock name from "carddetect" to "cd"
---
 Documentation/devicetree/bindings/mmc/tmio_mmc.txt | 13 +++++++++++++
 1 file changed, 13 insertions(+)

Comments

Rob Herring (Arm) Jan. 30, 2017, 8:37 p.m. UTC | #1

On Wed, Jan 25, 2017 at 03:28:09PM -0500, Chris Brandt wrote:
> In the case of a single clock source, you don't need names. However,
> if the controller has 2 clock sources, you need to name them correctly
> so the driver can find the 2nd one. The 2nd clock is for the internal
> card detect logic.
> 
> Signed-off-by: Chris Brandt <[e-mail]>
> Reviewed-by: Geert Uytterhoeven <[e-mail]>
> ---
> v5:
> * add Reviewed-by: Geert Uytterhoeven
> * list number of clocks for each SoC
> * remove example because it already exists in mmc.txt
> v4:
> * just explain there might be 2 clocks, don't explain how
>   we will use them in the driver
> v3:
> * add more clarification about why there are sometimes 2 clocks
>   and what you should do with them.
> * remove 'status = "disabled"' from example
> v2:
> * fix spelling and change wording
> * changed clock name from "carddetect" to "cd"
> ---
>  Documentation/devicetree/bindings/mmc/tmio_mmc.txt | 13 +++++++++++++
>  1 file changed, 13 insertions(+)

Acked-by: Rob Herring <[e-mail]>

Patch

diff --git a/Documentation/devicetree/bindings/mmc/tmio_mmc.txt b/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
index a1650ed..4fd8b7a 100644
--- a/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
+++ b/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
@@ -25,6 +25,19 @@  Required properties:
 		"renesas,sdhi-r8a7795" - SDHI IP on R8A7795 SoC
 		"renesas,sdhi-r8a7796" - SDHI IP on R8A7796 SoC
 
+- clocks: Most controllers only have 1 clock source per channel. However, on
+	  some variations of this controller, the internal card detection
+	  logic that exists in this controller is sectioned off to be run by a
+	  separate second clock source to allow the main core clock to be turned
+	  off to save power.
+	  If 2 clocks are specified by the hardware, you must name them as
+	  "core" and "cd". If the controller only has 1 clock, naming is not
+	  required.
+	  Below is the number clocks for each supported SoC:
+	   1: SH73A0, R8A73A4, R8A7740, R8A7778, R8A7779, R8A7790
+	      R8A7791, R8A7792, R8A7793, R8A7794, R8A7795, R8A7796
+	   2: R7S72100
+
 Optional properties:
 - toshiba,mmc-wrprotect-disable: write-protect detection is unavailable
 - pinctrl-names: should be "default", "state_uhs"