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@xxxxxxx> > --- > 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@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
