linux-kernel - [PATCH v2 2/2] mfd: intel-lpss: Introduce QUIRK_CLOCK_DIVIDER

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Date: Wed, 20 Dec 2023 21:56:21 +0100
From: Aleksandrs Vinarskis <alex.vinarskis@...il.com>
To: alex.vinarskis@...il.com
Cc: andriy.shevchenko@...ux.intel.com,
	hdegoede@...hat.com,
	lee@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] 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@...il.com>
---
V1 -> V2: Documented the quirk

 drivers/mfd/intel-lpss-pci.c | 3 +++
 drivers/mfd/intel-lpss.c     | 7 +++++++
 drivers/mfd/intel-lpss.h     | 5 +++++
 3 files changed, 15 insertions(+)

diff --git a/drivers/mfd/intel-lpss-pci.c b/drivers/mfd/intel-lpss-pci.c
index f8454d802677..951e28ca5e42 100644
--- a/drivers/mfd/intel-lpss-pci.c
+++ b/drivers/mfd/intel-lpss-pci.c
@@ -30,6 +30,9 @@ static const struct pci_device_id quirk_ids[] = {
 	}, {	/* Microsoft Surface Go 2 I2C4 */
 		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,
 	},
 	{}
 };
diff --git a/drivers/mfd/intel-lpss.c b/drivers/mfd/intel-lpss.c
index aafa0da5f8db..2a9018112dfc 100644
--- a/drivers/mfd/intel-lpss.c
+++ b/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);
diff --git a/drivers/mfd/intel-lpss.h b/drivers/mfd/intel-lpss.h
index 8a1ffd4f3546..8c032177611e 100644
--- a/drivers/mfd/intel-lpss.h
+++ b/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;
-- 
2.40.1