[PATCH v3 1/3] 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@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<|
'------------'

Acked-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
Reviewed-by: Anand Moon <linux.amoon@xxxxxxxxx>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
Signed-off-by: Marek Vasut <marek.vasut+renesas@xxxxxxxxxxx>
---
Cc: Bartosz Golaszewski <brgl@xxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Conor Dooley <conor+dt@xxxxxxxxxx>
Cc: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Cc: Krzysztof Kozlowski <krzk+dt@xxxxxxxxxx>
Cc: Magnus Damm <magnus.damm@xxxxxxxxx>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
Cc: Rob Herring <robh@xxxxxxxxxx>
Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
Cc: devicetree@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-pci@xxxxxxxxxxxxxxx
Cc: linux-renesas-soc@xxxxxxxxxxxxxxx
---
V2: - Fold PTR_ERR() into dev_err_probe()
    - Add RB from Anand and Manivannan
V3: - Rebase on top of PCI/pwrctrl: Fix double cleanup on devm_add_action_or_reset() failure
    - Move devm_clk_get_optional_enabled() below devm_add_action_or_reset()
    - Add AB from Bartosz
---
 drivers/pci/pwrctrl/slot.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/pci/pwrctrl/slot.c b/drivers/pci/pwrctrl/slot.c
index 26b21746da50b..3320494b62d89 100644
--- a/drivers/pci/pwrctrl/slot.c
+++ b/drivers/pci/pwrctrl/slot.c
@@ -4,6 +4,7 @@
  * Author: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
  */
 
+#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);
@@ -56,6 +58,12 @@ static int pci_pwrctrl_slot_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	clk = devm_clk_get_optional_enabled(dev, NULL);
+	if (IS_ERR(clk)) {
+		return dev_err_probe(dev, PTR_ERR(clk),
+				     "Failed to enable slot clock\n");
+	}
+
 	pci_pwrctrl_init(&slot->ctx, dev);
 
 	ret = devm_pci_pwrctrl_device_set_ready(dev, &slot->ctx);
-- 
2.47.2