diff mbox series

[3/6] dt-bindings: display: sitronix, st7735r: Remove spi-max-frequency limit

Message ID 20211124150757.17929-4-noralf@tronnes.org (mailing list archive)
State New, archived
Headers show
Series drm/tiny/st7735r: Match up with staging/fbtft driver | expand

Commit Message

Noralf Trønnes Nov. 24, 2021, 3:07 p.m. UTC
The datasheet lists the minimum Serial clock cycle (Write) as 66ns which is
15MHz. Mostly it can do much better than that and is in fact often run at
32MHz. With a clever driver that runs configuration commands at a low speed
and only the pixel data at the maximum speed the configuration can't be
messed up by transfer errors and the speed is only limited by the amount of
pixel glitches that one is able to tolerate.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---
 .../devicetree/bindings/display/sitronix,st7735r.yaml         | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

Comments

Rob Herring (Arm) Dec. 1, 2021, 9:57 p.m. UTC | #1
On Wed, 24 Nov 2021 16:07:54 +0100, Noralf Trønnes wrote:
> The datasheet lists the minimum Serial clock cycle (Write) as 66ns which is
> 15MHz. Mostly it can do much better than that and is in fact often run at
> 32MHz. With a clever driver that runs configuration commands at a low speed
> and only the pixel data at the maximum speed the configuration can't be
> messed up by transfer errors and the speed is only limited by the amount of
> pixel glitches that one is able to tolerate.
> 
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> ---
>  .../devicetree/bindings/display/sitronix,st7735r.yaml         | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 

Acked-by: Rob Herring <robh@kernel.org>
David Lechner Dec. 6, 2021, 3:19 p.m. UTC | #2
On 11/24/21 9:07 AM, Noralf Trønnes wrote:
> The datasheet lists the minimum Serial clock cycle (Write) as 66ns which is

Is this supposed to say "maximum" rather than "minimum"?

> 15MHz. Mostly it can do much better than that and is in fact often run at
> 32MHz. With a clever driver that runs configuration commands at a low speed
> and only the pixel data at the maximum speed the configuration can't be
> messed up by transfer errors and the speed is only limited by the amount of
> pixel glitches that one is able to tolerate.
> 
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> ---
Acked-by: David Lechner <david@lechnology.com>
Noralf Trønnes Dec. 6, 2021, 4:02 p.m. UTC | #3
Den 06.12.2021 16.19, skrev David Lechner:
> On 11/24/21 9:07 AM, Noralf Trønnes wrote:
>> The datasheet lists the minimum Serial clock cycle (Write) as 66ns
>> which is
> 
> Is this supposed to say "maximum" rather than "minimum"?
> 

Minimum cycle time == maximum frequency.

Noralf.

>> 15MHz. Mostly it can do much better than that and is in fact often run at
>> 32MHz. With a clever driver that runs configuration commands at a low
>> speed
>> and only the pixel data at the maximum speed the configuration can't be
>> messed up by transfer errors and the speed is only limited by the
>> amount of
>> pixel glitches that one is able to tolerate.
>>
>> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
>> ---
> Acked-by: David Lechner <david@lechnology.com>
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/display/sitronix,st7735r.yaml b/Documentation/devicetree/bindings/display/sitronix,st7735r.yaml
index f81d0d0d51fe..157b1a7b18f9 100644
--- a/Documentation/devicetree/bindings/display/sitronix,st7735r.yaml
+++ b/Documentation/devicetree/bindings/display/sitronix,st7735r.yaml
@@ -32,15 +32,13 @@  properties:
               - okaya,rh128128t
           - const: sitronix,st7715r
 
-  spi-max-frequency:
-    maximum: 32000000
-
   dc-gpios:
     maxItems: 1
     description: Display data/command selection (D/CX)
 
   backlight: true
   reg: true
+  spi-max-frequency: true
   reset-gpios: true
   rotation: true