PCI: faraday: Add clock handling

Add some optional clock handling to the Faraday FTPCI100.  We just get and
prepare+enable the clocks right now, if they exist.  We can add more
elaborate clock handling later.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
[bhelgaas: folded in "Make clocks compulsory" fix from
http://lkml.kernel.org/r/20170621085730.28804-1-linus.walleij@linaro.org
Also folded in the clock max/cur speed fixes from
http://lkml.kernel.org/r/20170621162651.25315-1-linus.walleij@linaro.org]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 56 insertions, 0 deletions

diff --git a/drivers/pci/host/pci-ftpci100.c b/drivers/pci/host/pci-ftpci100.c
index e938eebcb180..5162dffc102b 100644
--- a/drivers/pci/host/pci-ftpci100.c
+++ b/drivers/pci/host/pci-ftpci100.c
@@ -25,6 +25,7 @@
 #include <linux/irqchip/chained_irq.h>
 #include <linux/bitops.h>
 #include <linux/irq.h>
+#include <linux/clk.h>
 
 /*
  * Special configuration registers directly in the first few words
@@ -37,6 +38,7 @@
 #define PCI_CONFIG      0x28 /* PCI configuration command register */
 #define PCI_DATA        0x2C
 
+#define FARADAY_PCI_STATUS_CMD          0x04 /* Status and command */
 #define FARADAY_PCI_PMC                 0x40 /* Power management control */
 #define FARADAY_PCI_PMCSR               0x44 /* Power management status */
 #define FARADAY_PCI_CTRL1               0x48 /* Control register 1 */
@@ -45,6 +47,8 @@
 #define FARADAY_PCI_MEM2_BASE_SIZE      0x54 /* Memory base and size #2 */
 #define FARADAY_PCI_MEM3_BASE_SIZE      0x58 /* Memory base and size #3 */
 
+#define PCI_STATUS_66MHZ_CAPABLE        BIT(21)
+
 /* Bits 31..28 gives INTD..INTA status */
 #define PCI_CTRL2_INTSTS_SHIFT          28
 #define PCI_CTRL2_INTMASK_CMDERR        BIT(27)
@@ -117,6 +121,7 @@ struct faraday_pci {
         void __iomem *base;
         struct irq_domain *irqdomain;
         struct pci_bus *bus;
+        struct clk *bus_clk;
 };
 
 static int faraday_res_to_memcfg(resource_size_t mem_base,
@@ -444,6 +449,9 @@ static int faraday_pci_probe(struct platform_device *pdev)
         struct resource *mem;
         struct resource *io;
         struct pci_host_bridge *host;
+        struct clk *clk;
+        unsigned char max_bus_speed = PCI_SPEED_33MHz;
+        unsigned char cur_bus_speed = PCI_SPEED_33MHz;
         int ret;
         u32 val;
         LIST_HEAD(res);
@@ -462,6 +470,24 @@ static int faraday_pci_probe(struct platform_device *pdev)
         host->sysdata = p;
         p->dev = dev;
 
+        /* Retrieve and enable optional clocks */
+        clk = devm_clk_get(dev, "PCLK");
+        if (IS_ERR(clk))
+                return PTR_ERR(clk);
+        ret = clk_prepare_enable(clk);
+        if (ret) {
+                dev_err(dev, "could not prepare PCLK\n");
+                return ret;
+        }
+        p->bus_clk = devm_clk_get(dev, "PCICLK");
+        if (IS_ERR(p->bus_clk))
+                return PTR_ERR(clk);
+        ret = clk_prepare_enable(p->bus_clk);
+        if (ret) {
+                dev_err(dev, "could not prepare PCICLK\n");
+                return ret;
+        }
+
         regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
         p->base = devm_ioremap_resource(dev, regs);
         if (IS_ERR(p->base))
@@ -524,6 +550,34 @@ static int faraday_pci_probe(struct platform_device *pdev)
                 }
         }
 
+        /* Check bus clock if we can gear up to 66 MHz */
+        if (!IS_ERR(p->bus_clk)) {
+                unsigned long rate;
+                u32 val;
+
+                faraday_raw_pci_read_config(p, 0, 0,
+                                            FARADAY_PCI_STATUS_CMD, 4, &val);
+                rate = clk_get_rate(p->bus_clk);
+
+                if ((rate == 33000000) && (val & PCI_STATUS_66MHZ_CAPABLE)) {
+                        dev_info(dev, "33MHz bus is 66MHz capable\n");
+                        max_bus_speed = PCI_SPEED_66MHz;
+                        ret = clk_set_rate(p->bus_clk, 66000000);
+                        if (ret)
+                                dev_err(dev, "failed to set bus clock\n");
+                } else {
+                        dev_info(dev, "33MHz only bus\n");
+                        max_bus_speed = PCI_SPEED_33MHz;
+                }
+
+                /* Bumping the clock may fail so read back the rate */
+                rate = clk_get_rate(p->bus_clk);
+                if (rate == 33000000)
+                        cur_bus_speed = PCI_SPEED_33MHz;
+                if (rate == 66000000)
+                        cur_bus_speed = PCI_SPEED_66MHz;
+        }
+
         ret = faraday_pci_parse_map_dma_ranges(p, dev->of_node);
         if (ret)
                 return ret;
@@ -535,6 +589,8 @@ static int faraday_pci_probe(struct platform_device *pdev)
                 return ret;
         }
         p->bus = host->bus;
+        p->bus->max_bus_speed = max_bus_speed;
+        p->bus->cur_bus_speed = cur_bus_speed;
 
         pci_bus_assign_resources(p->bus);
         pci_bus_add_devices(p->bus);