mfd: intel-lpss: Introduce QUIRK_CLOCK_DIVIDER_UNITY for XPS 9530

Some devices (eg. Dell XPS 9530, 2023) due to a firmware bug have a
misconfigured clock divider, which should've been 1:1. This introduces
quirk which conditionally re-configures the clock divider to 1:1.
Signed-off-by: Aleksandrs Vinarskis <alex.vinarskis@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20231221185142.9224-3-alex.vinarskis@gmail.comSigned-off-by: Lee Jones <lee@kernel.org>

drivers/mfd/intel-lpss-pci.c

@@ -34,6 +34,11 @@ static const struct pci_device_id quirk_ids[] = {
 		PCI_DEVICE_SUB(PCI_VENDOR_ID_INTEL, 0x9d64, 0x152d, 0x1237),
 		.driver_data = QUIRK_IGNORE_RESOURCE_CONFLICTS,
 	},
+	{
+		/* Dell XPS 9530 (2023) */
+		PCI_DEVICE_SUB(PCI_VENDOR_ID_INTEL, 0x51fb, 0x1028, 0x0beb),
+		.driver_data = QUIRK_CLOCK_DIVIDER_UNITY,
+	},
 	{ }
 };
 

drivers/mfd/intel-lpss.c

@@ -300,6 +300,7 @@ static int intel_lpss_register_clock_divider(struct intel_lpss *lpss,
 {
 	char name[32];
 	struct clk *tmp = *clk;
+	int ret;
 
 	snprintf(name, sizeof(name), "%s-enable", devname);
 	tmp = clk_register_gate(NULL, name, __clk_get_name(tmp), 0,
@@ -316,6 +317,12 @@ static int intel_lpss_register_clock_divider(struct intel_lpss *lpss,
 		return PTR_ERR(tmp);
 	*clk = tmp;
 
+	if (lpss->info->quirks & QUIRK_CLOCK_DIVIDER_UNITY) {
+		ret = clk_set_rate(tmp, lpss->info->clk_rate);
+		if (ret)
+			return ret;
+	}
+
 	snprintf(name, sizeof(name), "%s-update", devname);
 	tmp = clk_register_gate(NULL, name, __clk_get_name(tmp),
 				CLK_SET_RATE_PARENT, lpss->priv, 31, 0, NULL);

drivers/mfd/intel-lpss.h

@@ -19,6 +19,11 @@
  * Set to ignore resource conflicts with ACPI declared SystemMemory regions.
  */
 #define QUIRK_IGNORE_RESOURCE_CONFLICTS BIT(0)
+/*
+ * Some devices have misconfigured clock divider due to a firmware bug.
+ * Set this to force the clock divider to 1:1 ratio.
+ */
+#define QUIRK_CLOCK_DIVIDER_UNITY		BIT(1)
 
 struct device;
 struct resource;