i3c: mipi-i3c-hci: Add a quirk to set timing parameters

The AMD HCI controller is currently unstable at 12.5 MHz. To address this,
a quirk is added to configure the clock rate to 9 MHz as a workaround,
with proportional adjustments to the Open-Drain (OD) and Push-Pull (PP)
values.

Reviewed-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Co-developed-by: Guruvendra Punugupati <Guruvendra.Punugupati@amd.com>
Signed-off-by: Guruvendra Punugupati <Guruvendra.Punugupati@amd.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Link: https://lore.kernel.org/r/20240829091713.736217-6-Shyam-sundar.S-k@amd.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/i3c/master/mipi-i3c-hci/Makefile

@@ -3,4 +3,5 @@
 obj-$(CONFIG_MIPI_I3C_HCI)		+= mipi-i3c-hci.o
 mipi-i3c-hci-y				:= core.o ext_caps.o pio.o dma.o \
 					   cmd_v1.o cmd_v2.o \
-					   dat_v1.o dct_v1.o
+					   dat_v1.o dct_v1.o \
+					   hci_quirks.o

drivers/i3c/master/mipi-i3c-hci/core.c

@@ -785,6 +785,10 @@ static int i3c_hci_init(struct i3c_hci *hci)
 		return ret;
 	}
 
+	/* Configure OD and PP timings for AMD platforms */
+	if (hci->quirks & HCI_QUIRK_OD_PP_TIMING)
+		amd_set_od_pp_timing(hci);
+
 	return 0;
 }
 
@@ -838,7 +842,7 @@ static const __maybe_unused struct of_device_id i3c_hci_of_match[] = {
 MODULE_DEVICE_TABLE(of, i3c_hci_of_match);
 
 static const struct acpi_device_id i3c_hci_acpi_match[] = {
-	{ "AMDI5017", HCI_QUIRK_PIO_MODE },
+	{ "AMDI5017", HCI_QUIRK_PIO_MODE | HCI_QUIRK_OD_PP_TIMING },
 	{}
 };
 MODULE_DEVICE_TABLE(acpi, i3c_hci_acpi_match);

drivers/i3c/master/mipi-i3c-hci/hci.h

@@ -141,11 +141,13 @@ struct i3c_hci_dev_data {
 /* list of quirks */
 #define HCI_QUIRK_RAW_CCC	BIT(1)	/* CCC framing must be explicit */
 #define HCI_QUIRK_PIO_MODE	BIT(2)  /* Set PIO mode for AMD platforms */
+#define HCI_QUIRK_OD_PP_TIMING		BIT(3)  /* Set OD and PP timings for AMD platforms */
 
 
 /* global functions */
 void mipi_i3c_hci_resume(struct i3c_hci *hci);
 void mipi_i3c_hci_pio_reset(struct i3c_hci *hci);
 void mipi_i3c_hci_dct_index_reset(struct i3c_hci *hci);
+void amd_set_od_pp_timing(struct i3c_hci *hci);
 
 #endif

drivers/i3c/master/mipi-i3c-hci/hci_quirks.c

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * I3C HCI Quirks
+ *
+ * Copyright 2024 Advanced Micro Devices, Inc.
+ *
+ * Authors: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
+ *	    Guruvendra Punugupati <Guruvendra.Punugupati@amd.com>
+ */
+
+#include <linux/i3c/master.h>
+#include "hci.h"
+
+/* Timing registers */
+#define HCI_SCL_I3C_OD_TIMING          0x214
+#define HCI_SCL_I3C_PP_TIMING          0x218
+#define HCI_SDA_HOLD_SWITCH_DLY_TIMING 0x230
+
+/* Timing values to configure 9MHz frequency */
+#define AMD_SCL_I3C_OD_TIMING          0x00cf00cf
+#define AMD_SCL_I3C_PP_TIMING          0x00160016
+
+void amd_set_od_pp_timing(struct i3c_hci *hci)
+{
+	u32 data;
+
+	reg_write(HCI_SCL_I3C_OD_TIMING, AMD_SCL_I3C_OD_TIMING);
+	reg_write(HCI_SCL_I3C_PP_TIMING, AMD_SCL_I3C_PP_TIMING);
+	data = reg_read(HCI_SDA_HOLD_SWITCH_DLY_TIMING);
+	/* Configure maximum TX hold time */
+	data |= W0_MASK(18, 16);
+	reg_write(HCI_SDA_HOLD_SWITCH_DLY_TIMING, data);
+}