[PATCH 1/2] PCI/pwrctrl: Add optional slot clock to pwrctrl driver for PCI slots

[Marek Vasut]

Add the ability to enable optional slot clock into the pwrctrl driver.
This is used to enable slot clock in split-clock topologies, where the
PCIe host/controller supply and PCIe slot supply are not provided by
the same clock. The PCIe host/controller clock should be described in
the controller node as the controller clock, while the slot clock should
be described in controller bridge/slot subnode.

Example DT snippet:
&pcicontroller {
    clocks = <&clk_dif 0>;             /* PCIe controller clock */

    pci at 0,0 {
        #address-cells = <3>;
        #size-cells = <2>;
        reg = <0x0 0x0 0x0 0x0 0x0>;
        compatible = "pciclass,0604";
        device_type = "pci";
        clocks = <&clk_dif 1>;         /* PCIe slot clock */
        vpcie3v3-supply = <&reg_3p3v>;
        ranges;
    };
};

Example clock topology:
 ____________                    ____________
|  PCIe host |                  | PCIe slot  |
|            |                  |            |
|    PCIe RX<|==================|>PCIe TX    |
|    PCIe TX<|==================|>PCIe RX    |
|            |                  |            |
|   PCIe CLK<|======..  ..======|>PCIe CLK   |
'------------'      ||  ||      '------------'
                    ||  ||
 ____________       ||  ||
|  9FGV0441  |      ||  ||
|            |      ||  ||
|   CLK DIF0<|======''  ||
|   CLK DIF1<|==========''
|   CLK DIF2<|
|   CLK DIF3<|
'------------'

Signed-off-by: Marek Vasut <marek.vasut+renesas at mailbox.org>
---
Cc: Bartosz Golaszewski <brgl at bgdev.pl>
Cc: Bjorn Helgaas <bhelgaas at google.com>
Cc: Conor Dooley <conor+dt at kernel.org>
Cc: Geert Uytterhoeven <geert+renesas at glider.be>
Cc: Krzysztof Kozlowski <krzk+dt at kernel.org>
Cc: Magnus Damm <magnus.damm at gmail.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam at linaro.org>
Cc: Rob Herring <robh at kernel.org>
Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh at renesas.com>
Cc: devicetree at vger.kernel.org
Cc: linux-kernel at vger.kernel.org
Cc: linux-pci at vger.kernel.org
Cc: linux-renesas-soc at vger.kernel.org
---
 drivers/pci/pwrctrl/slot.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/pci/pwrctrl/slot.c b/drivers/pci/pwrctrl/slot.c
index 18becc144913e..222c14056cfae 100644
--- a/drivers/pci/pwrctrl/slot.c
+++ b/drivers/pci/pwrctrl/slot.c
@@ -4,6 +4,7 @@
  * Author: Manivannan Sadhasivam <manivannan.sadhasivam at linaro.org>
  */
 
+#include <linux/clk.h>
 #include <linux/device.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
@@ -30,6 +31,7 @@ static int pci_pwrctrl_slot_probe(struct platform_device *pdev)
 {
 	struct pci_pwrctrl_slot_data *slot;
 	struct device *dev = &pdev->dev;
+	struct clk *clk;
 	int ret;
 
 	slot = devm_kzalloc(dev, sizeof(*slot), GFP_KERNEL);
@@ -50,6 +52,13 @@ static int pci_pwrctrl_slot_probe(struct platform_device *pdev)
 		goto err_regulator_free;
 	}
 
+	clk = devm_clk_get_optional_enabled(dev, NULL);
+	if (IS_ERR(clk)) {
+		ret = PTR_ERR(clk);
+		dev_err_probe(dev, ret, "Failed to enable slot clock\n");
+		goto err_regulator_disable;
+	}
+
 	ret = devm_add_action_or_reset(dev, devm_pci_pwrctrl_slot_power_off,
 				       slot);
 	if (ret)
-- 
2.47.2