[PATCH v2 0/2] ARM: dts: rockchip: pull up cts lines

[PATCH v2 0/2] ARM: dts: rockchip: pull up cts lines

[Alexandru M Stan]

The flow control lines from a user accessible UART are optional,
the user might not have anything connected to those pins.
In order to prevent random interrupts happening and noise affecting
the cts pin should be pulled up.

The only boards affected (that care about uart*_cts ) are the veyron
chromeos devices and the firefly. Veyron already has something like that,
which I now have to remove in the second patch. Firefly uses uart0_cts
for the wifi chip communications, same thing as veyron, so it should be
fine having it.

Changes in v2:
- Restrict changes only to cts pin, leave rts alone
- CC people with the firefly board
- New patch removing redundant pullup code from veyron
- cover letter

Alexandru M Stan (2):
  ARM: dts: rockchip: pull up cts lines on rk3288
  ARM: dts: rockchip: Remove specific cts pullup from veyron

 arch/arm/boot/dts/rk3288-veyron.dtsi | 12 ------------
 arch/arm/boot/dts/rk3288.dtsi        |  8 ++++----
 2 files changed, 4 insertions(+), 16 deletions(-)

-- 
2.5.0.457.gab17608

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[PATCH v2 1/2] ARM: dts: rockchip: pull up cts lines on rk3288

[Alexandru M Stan]

The flow control lines from a user accessible UART are optional,
the user might not have anything connected to those pins.
In order to prevent random interrupts happening and noise affecting
the cts pin should be pulled up.

Note that the default state for that pin on the rk3288 is pulled up,
so this patch merely restores them.

This is similar to what we're already doing with the RX pin,
so it should be safe. At worst it might be a slightly higher power usage
(through ~50 kohms) when the cts is low.

Suggested-by: Neil Hendin <nhendin@chromium.org>
Signed-off-by: Alexandru M Stan <amstan@chromium.org>
---
Changes in v2: None

 arch/arm/boot/dts/rk3288.dtsi | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm/boot/dts/rk3288.dtsi b/arch/arm/boot/dts/rk3288.dtsi
index 906e938..0e8fd53 100644
--- a/arch/arm/boot/dts/rk3288.dtsi
+++ b/arch/arm/boot/dts/rk3288.dtsi
@@ -1211,7 +1211,7 @@
 			};
 
 			uart0_cts: uart0-cts {
-				rockchip,pins = <4 18 RK_FUNC_1 &pcfg_pull_none>;
+				rockchip,pins = <4 18 RK_FUNC_1 &pcfg_pull_up>;
 			};
 
 			uart0_rts: uart0-rts {
@@ -1226,7 +1226,7 @@
 			};
 
 			uart1_cts: uart1-cts {
-				rockchip,pins = <5 10 RK_FUNC_1 &pcfg_pull_none>;
+				rockchip,pins = <5 10 RK_FUNC_1 &pcfg_pull_up>;
 			};
 
 			uart1_rts: uart1-rts {
@@ -1249,7 +1249,7 @@
 			};
 
 			uart3_cts: uart3-cts {
-				rockchip,pins = <7 9 RK_FUNC_1 &pcfg_pull_none>;
+				rockchip,pins = <7 9 RK_FUNC_1 &pcfg_pull_up>;
 			};
 
 			uart3_rts: uart3-rts {
@@ -1264,7 +1264,7 @@
 			};
 
 			uart4_cts: uart4-cts {
-				rockchip,pins = <5 14 3 &pcfg_pull_none>;
+				rockchip,pins = <5 14 3 &pcfg_pull_up>;
 			};
 
 			uart4_rts: uart4-rts {
-- 
2.5.0.457.gab17608

Re: [PATCH v2 1/2] ARM: dts: rockchip: pull up cts lines on rk3288

[Doug Anderson]

Alex,

On Wed, Sep 2, 2015 at 4:27 PM, Alexandru M Stan <amstan@chromium.org> wrote:
> The flow control lines from a user accessible UART are optional,
> the user might not have anything connected to those pins.
> In order to prevent random interrupts happening and noise affecting
> the cts pin should be pulled up.
>
> Note that the default state for that pin on the rk3288 is pulled up,
> so this patch merely restores them.
>
> This is similar to what we're already doing with the RX pin,
> so it should be safe. At worst it might be a slightly higher power usage
> (through ~50 kohms) when the cts is low.
>
> Suggested-by: Neil Hendin <nhendin@chromium.org>
> Signed-off-by: Alexandru M Stan <amstan@chromium.org>
> ---
> Changes in v2: None

Probably not entirely true.  ;)

>  arch/arm/boot/dts/rk3288.dtsi | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)

Looks good to me.

Reviewed-by: Douglas Anderson <dianders@chromium.org>

[PATCH v2 2/2] ARM: dts: rockchip: Remove specific cts pullup from veyron

[Alexandru M Stan]

With the previous patch ("rk3288: pull up cts lines") this is redundant,
I sent that patch for the same reason this existed here, so the lines don't
wiggle randomly when disconnected.

Signed-off-by: Alexandru M Stan <amstan@chromium.org>
---
Changes in v2:
- Restrict changes only to cts pin, leave rts alone
- CC people with the firefly board
- New patch removing redundant pullup code from veyron
- cover letter

 arch/arm/boot/dts/rk3288-veyron.dtsi | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/arch/arm/boot/dts/rk3288-veyron.dtsi b/arch/arm/boot/dts/rk3288-veyron.dtsi
index 2fa7a0d..2b5d2e2 100644
--- a/arch/arm/boot/dts/rk3288-veyron.dtsi
+++ b/arch/arm/boot/dts/rk3288-veyron.dtsi
@@ -543,18 +543,6 @@
 		};
 	};
 
-	/*
-	 * On Marvell-based hardware this is a no-connect.  Make sure we enable
-	 * the pullup so that the line doesn't float.  The pullup shouldn't
-	 * hurt on Broadcom-based hardware since the other side is actively
-	 * driving this signal.  As proof: we've already got a pullup on RX.
-	 */
-	uart0 {
-		uart0_cts: uart0-cts {
-			rockchip,pins = <4 18 RK_FUNC_1 &pcfg_pull_up>;
-		};
-	};
-
 	write-protect {
 		fw_wp_ap: fw-wp-ap {
 			rockchip,pins = <7 6 RK_FUNC_GPIO &pcfg_pull_none>;
-- 
2.5.0.457.gab17608

Re: [PATCH v2 2/2] ARM: dts: rockchip: Remove specific cts pullup from veyron

[Doug Anderson]

Alex,

On Wed, Sep 2, 2015 at 4:27 PM, Alexandru M Stan <amstan-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org> wrote:
> With the previous patch ("rk3288: pull up cts lines") this is redundant,
> I sent that patch for the same reason this existed here, so the lines don't
> wiggle randomly when disconnected.
>
> Signed-off-by: Alexandru M Stan <amstan-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> ---
> Changes in v2:
> - Restrict changes only to cts pin, leave rts alone
> - CC people with the firefly board
> - New patch removing redundant pullup code from veyron
> - cover letter
>
>  arch/arm/boot/dts/rk3288-veyron.dtsi | 12 ------------
>  1 file changed, 12 deletions(-)

Reviewed-by: Douglas Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
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Re: [PATCH v2 0/2] ARM: dts: rockchip: pull up cts lines

[Heiko Stuebner]

Hi Alex,

Am Mittwoch, 2. September 2015, 16:27:57 schrieb Alexandru M Stan:
> The flow control lines from a user accessible UART are optional,
> the user might not have anything connected to those pins.
> In order to prevent random interrupts happening and noise affecting
> the cts pin should be pulled up.
> 
> The only boards affected (that care about uart*_cts ) are the veyron
> chromeos devices and the firefly. Veyron already has something like that,
> which I now have to remove in the second patch. Firefly uses uart0_cts
> for the wifi chip communications, same thing as veyron, so it should be
> fine having it.

applied both to my dts branch for 4.4 with Doug's Review-tag
(Currently only on github and becomes really public after 4.3-rc1)


Heiko
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