PCI: qcom: Don't deassert reset GPIO during probe

Message ID 20190125232616.25714-1-bjorn.andersson@linaro.org
State New
Headers show
Series
  • PCI: qcom: Don't deassert reset GPIO during probe
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Commit Message

Bjorn Andersson Jan. 25, 2019, 11:26 p.m.
Acquiring the reset GPIO low means that reset is being deasserted, this
is followed almost immediately with qcom_pcie_host_init() asserting it,
initializing it and then finally deasserting it again, for the link to
come up.

Some PCIe devices requires a minimum time between the initial deassert
and subsequent reset cycles. In a platform that boots with the reset
GPIO asserted this requirement is being violated by this deassert/assert
pulse.

Acquiring the reset GPIO high will prevent this by matching the state to
the subsequent asserted state.

Cc: stable@vger.kernel.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

---
 drivers/pci/controller/dwc/pcie-qcom.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
2.18.0

Comments

Lorenzo Pieralisi Feb. 13, 2019, 3:23 p.m. | #1
On Fri, Jan 25, 2019 at 03:26:16PM -0800, Bjorn Andersson wrote:
> Acquiring the reset GPIO low means that reset is being deasserted, this

> is followed almost immediately with qcom_pcie_host_init() asserting it,

> initializing it and then finally deasserting it again, for the link to

> come up.

> 

> Some PCIe devices requires a minimum time between the initial deassert

> and subsequent reset cycles. In a platform that boots with the reset

> GPIO asserted this requirement is being violated by this deassert/assert

> pulse.

> 

> Acquiring the reset GPIO high will prevent this by matching the state to

> the subsequent asserted state.

> 

> Cc: stable@vger.kernel.org


Missing Fixes: tag, please provide me one so that I can proceed.

Lorenzo

> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

> ---

>  drivers/pci/controller/dwc/pcie-qcom.c | 2 +-

>  1 file changed, 1 insertion(+), 1 deletion(-)

> 

> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c

> index d185ea5fe996..a7f703556790 100644

> --- a/drivers/pci/controller/dwc/pcie-qcom.c

> +++ b/drivers/pci/controller/dwc/pcie-qcom.c

> @@ -1228,7 +1228,7 @@ static int qcom_pcie_probe(struct platform_device *pdev)

>  

>  	pcie->ops = of_device_get_match_data(dev);

>  

> -	pcie->reset = devm_gpiod_get_optional(dev, "perst", GPIOD_OUT_LOW);

> +	pcie->reset = devm_gpiod_get_optional(dev, "perst", GPIOD_OUT_HIGH);

>  	if (IS_ERR(pcie->reset)) {

>  		ret = PTR_ERR(pcie->reset);

>  		goto err_pm_runtime_put;

> -- 

> 2.18.0

>

Patch

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index d185ea5fe996..a7f703556790 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -1228,7 +1228,7 @@  static int qcom_pcie_probe(struct platform_device *pdev)
 
 	pcie->ops = of_device_get_match_data(dev);
 
-	pcie->reset = devm_gpiod_get_optional(dev, "perst", GPIOD_OUT_LOW);
+	pcie->reset = devm_gpiod_get_optional(dev, "perst", GPIOD_OUT_HIGH);
 	if (IS_ERR(pcie->reset)) {
 		ret = PTR_ERR(pcie->reset);
 		goto err_pm_runtime_put;