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[1/4] devicetree: bindings: pci: document tx-deempth tx swing and rx-eq property

Message ID 20200410004738.19668-2-ansuelsmth@gmail.com
State New
Headers show
Series Move tx-deempth and tx swing to pci.txt | expand

Commit Message

Ansuel Smith April 10, 2020, 12:47 a.m. UTC
Document tx-deempth, tx swing and rx-eq property property used on some
device (qcom ipq806x or imx6q) to tune and fix init error of the pci
bridge.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
 Documentation/devicetree/bindings/pci/pci.txt | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

Comments

Florian Fainelli April 13, 2020, 8:29 p.m. UTC | #1
On 4/9/2020 5:47 PM, Ansuel Smith wrote:
> Document tx-deempth, tx swing and rx-eq property property used on some
> device (qcom ipq806x or imx6q) to tune and fix init error of the pci
> bridge.

Those properties are not specific to the host bridge per-se, but to the
PCIe PHY, therefore, one would expect to find those properties within
the PCIe PHY node if it exists. Given you want this binding to be
generic, this is an important thing to correct here.
Bjorn Helgaas April 13, 2020, 8:40 p.m. UTC | #2
Looks like "dt-bindings: PCI: " is the convention here.

  $ git log --oneline Documentation/devicetree/bindings/pci/
  11be8af70d86 dt-bindings: PCI: Convert PCIe Host/Endpoint in Cadence platform to DT schema
  69501078fc60 dt-bindings: PCI: cadence: Add PCIe RC/EP DT schema for Cadence PCIe
  847dbf4e1aba dt-bindings: PCI: Add PCI Endpoint Controller Schema
  f9f711efd441 arm64: tegra: Fix Tegra194 PCIe compatible string
  9f04d18b1edf dt-bindings: PCI: tegra: Add DT support for PCIe EP nodes in Tegra194
  6e5f77031cc9 dt-bindings: PCI: meson: Update PCIE bindings documentation
  3edeb49525bb dt-bindings: PCI: Add NXP Layerscape SoCs PCIe Gen4 controller
  34129bb831cc dt-bindings: PCI: intel: Fix dt_binding_check compilation failure

On Fri, Apr 10, 2020 at 02:47:35AM +0200, Ansuel Smith wrote:
> Document tx-deempth, tx swing and rx-eq property property used on some
> device (qcom ipq806x or imx6q) to tune and fix init error of the pci
> bridge.

s/tx-deempth/tx-deemph/ (in subject and commit log)
s/tx swing/tx-swing/ (both places also)
s/rx-eq/rx-equalization/ (ditto)
s/property property/properties/
s/pci/PCI/ in English text (not C variables, function names, etc).

If these are made generic, remove the "qcom ipq806x or imx6q" part.

> Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
> ---
>  Documentation/devicetree/bindings/pci/pci.txt | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pci/pci.txt b/Documentation/devicetree/bindings/pci/pci.txt
> index 29bcbd88f457..df37486f1853 100644
> --- a/Documentation/devicetree/bindings/pci/pci.txt
> +++ b/Documentation/devicetree/bindings/pci/pci.txt
> @@ -24,6 +24,24 @@ driver implementation may support the following properties:
>     unsupported link speed, for instance, trying to do training for
>     unsupported link speed, etc.  Must be '4' for gen4, '3' for gen3, '2'
>     for gen2, and '1' for gen1. Any other values are invalid.
> +- tx-deemph-gen1
> +   If present this property will tune the Transmit De-Emphasis level for GEN1 if
> +   supported by the driver.
> +- tx-deemph-gen2-3p5db
> +   If present this property will tune the Transmit De-Emphasis level for GEN2 in
> +   3.5db band if supported by the driver.
> +- tx-deempth-gen2-6db
> +   If present this property will tune the Transmit De-Emphasis level for GEN2 in
> +   6db band if supported by the driver.
> +- tx-swing-full
> +   If present this property will tune the Tx Swing Full value if supported by the
> +   driver.
> +- tx-swing-low
> +   If present this property will tune the Tx Swing Low value if supported by the

Wrap all of these to fit in 78 columns.  Some of them fit in 80
columns, which is sort of OK.  This one is 81, which is definitely too
long.

> +   driver.
> +- rx-equalization
> +   If present this property will tune the Rx equalization value if supported by
> +   the driver.
>  - reset-gpios:
>     If present this property specifies PERST# GPIO. Host drivers can parse the
>     GPIO and apply fundamental reset to endpoints.
> -- 
> 2.25.1
>
Ansuel Smith April 14, 2020, 12:51 p.m. UTC | #3
> On 4/9/2020 5:47 PM, Ansuel Smith wrote:
> > Document tx-deempth, tx swing and rx-eq property property used on
> some
> > device (qcom ipq806x or imx6q) to tune and fix init error of the pci
> > bridge.
> 
> Those properties are not specific to the host bridge per-se, but to the
> PCIe PHY, therefore, one would expect to find those properties within
> the PCIe PHY node if it exists. Given you want this binding to be
> generic, this is an important thing to correct here.
> --
> Florian

So where should I put these? If I understand this properly I should move 
this to the PHY directory but no PCIe PHY node exist for both imx6q 
and ipq806x. How I should proceed? 
It would be better to just drop this and add qcom specific binding to the
driver?
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/pci/pci.txt b/Documentation/devicetree/bindings/pci/pci.txt
index 29bcbd88f457..df37486f1853 100644
--- a/Documentation/devicetree/bindings/pci/pci.txt
+++ b/Documentation/devicetree/bindings/pci/pci.txt
@@ -24,6 +24,24 @@  driver implementation may support the following properties:
    unsupported link speed, for instance, trying to do training for
    unsupported link speed, etc.  Must be '4' for gen4, '3' for gen3, '2'
    for gen2, and '1' for gen1. Any other values are invalid.
+- tx-deemph-gen1
+   If present this property will tune the Transmit De-Emphasis level for GEN1 if
+   supported by the driver.
+- tx-deemph-gen2-3p5db
+   If present this property will tune the Transmit De-Emphasis level for GEN2 in
+   3.5db band if supported by the driver.
+- tx-deempth-gen2-6db
+   If present this property will tune the Transmit De-Emphasis level for GEN2 in
+   6db band if supported by the driver.
+- tx-swing-full
+   If present this property will tune the Tx Swing Full value if supported by the
+   driver.
+- tx-swing-low
+   If present this property will tune the Tx Swing Low value if supported by the
+   driver.
+- rx-equalization
+   If present this property will tune the Rx equalization value if supported by
+   the driver.
 - reset-gpios:
    If present this property specifies PERST# GPIO. Host drivers can parse the
    GPIO and apply fundamental reset to endpoints.