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| author | Petr Štetiar <ynezz@true.cz> | 2016-04-20 03:42:07 +0300 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2016-04-20 03:42:07 +0300 |
| commit | 3ea8529acc30467331b7b1f5da6cf668fac091c7 (patch) | |
| tree | 2d08f8d8e392a3badf9e25e1f78932498b0c3d16 /Documentation | |
| parent | 4f6926e9fdf94208dc37da0cd17835328fa4dbba (diff) | |
| download | linux-3ea8529acc30467331b7b1f5da6cf668fac091c7.tar.xz | |
PCI: imx6: Add reset-gpio-active-high boolean property to DT
Currently the reset-gpio DT property which controls the PCI bus device
reset signal defaults to active-low reset sequence (L=reset state,
H=operation state) plus the code in reset function isn't GPIO polarity
aware - it doesn't matter if the defined reset-gpio is active-low or
active-high, it will always result into active-low reset sequence.
I've tried to fix it properly and change the reset-gpio reset sequence to
be polarity-aware, but this patch has been accepted and then reverted as it
has introduced few backward incompatible issues:
1. Some DTBs, for example, imx6qdl-sabresd, don't define reset-gpio
polarity correctly:
reset-gpio = <&gpio7 12 0>;
which means that it's defined as active-high, but in reality it's
active-low; thus it wouldn't work without a DTS fix.
2. The logic in the reset function is inverted:
gpio_set_value_cansleep(imx6_pcie->reset_gpio, 0)
msleep(100);
gpio_set_value_cansleep(imx6_pcie->reset_gpio, 1);
so even if some of the i.MX6 boards had reset-gpio polarity defined
correctly in their DTSes, they would stop working.
As we can't break old DTBs, we can't fix them, so we need to introduce this
new DT reset-gpio-active-high boolean property so we can support boards
with active-high reset sequence.
This active-high reset sequence is for example needed on Apalis SoMs, where
GPIO1_IO28, used to PCIe reset is not connected directly to PERST# PCIe
signal, but it's ORed with RESETBMCU coming off the PMIC, and thus is
inverted, active-high.
Tested-by: Tim Harvey <tharvey@gateworks.com> # Gateworks Ventana boards (which have active-low PERST#)
Signed-off-by: Petr Štetiar <ynezz@true.cz>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Rob Herring <robh@kernel.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt index 0561e88f3b37..636707df0952 100644 --- a/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt +++ b/Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt @@ -19,6 +19,12 @@ Optional properties: - fsl,tx-deemph-gen2-6db: Gen2 (6db) De-emphasis value. Default: 20 - fsl,tx-swing-full: Gen2 TX SWING FULL value. Default: 127 - fsl,tx-swing-low: TX launch amplitude swing_low value. Default: 127 +- reset-gpio: Should specify the GPIO for controlling the PCI bus device reset + signal. It's not polarity aware and defaults to active-low reset sequence + (L=reset state, H=operation state). +- reset-gpio-active-high: If present then the reset sequence using the GPIO + specified in the "reset-gpio" property is reversed (H=reset state, + L=operation state). Additional required properties for imx6sx-pcie: - clock names: Must include the following additional entries: |