Re: [PATCH v3 2/2] PCI: imx6: Add reset-gpio-active-high boolean property to DT

[Rob Herring <robh@kernel.org>]

On Wed, Apr 06, 2016 at 02:36:47PM +0200, Petr Štetiar wrote:
> 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 changed 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 of the DTBs as for example imx6qdl-sabresd, doesn'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 DTS fix.
> 
> 2. The logic in 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 and that's why 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.
> 
> Signed-off-by: Petr Štetiar <ynezz@true.cz>
> ---
>  Changes since v1:
> 
>   * Added documentation of reset-gpio and reset-gpio-active-high DT properties
>   * Removed unnecessary double negation of GPIO value
> 
>  Changes since v2:
> 
>   * Changed commit message so it explains in more detail why we need new DT
>     property
>   * Changed PHY to 'bus device' in binding's documentation
> 
>  Documentation/devicetree/bindings/pci/fsl,imx6q-pcie.txt |  6 ++++++
>  drivers/pci/host/pci-imx6.c                              | 14 +++++++++++---
>  2 files changed, 17 insertions(+), 3 deletions(-)

Acked-by: Rob Herring <robh@kernel.org>