linux-kernel - [PATCH 4/5] i3c: mipi-i3c-hci: Add a quirk to set timing parameters

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Message-ID: <20240723173538.3493935-5-Shyam-sundar.S-k@amd.com>
Date: Tue, 23 Jul 2024 23:05:37 +0530
From: Shyam Sundar S K <Shyam-sundar.S-k@....com>
To: Alexandre Belloni <alexandre.belloni@...tlin.com>, Jarkko Nikula
	<jarkko.nikula@...ux.intel.com>
CC: Guruvendra Punugupati <Guruvendra.Punugupati@....com>, Krishnamoorthi M
	<krishnamoorthi.m@....com>, <linux-i3c@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, Shyam Sundar S K <Shyam-sundar.S-k@....com>
Subject: [PATCH 4/5] 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.

Co-developed-by: Guruvendra Punugupati <Guruvendra.Punugupati@....com>
Signed-off-by: Guruvendra Punugupati <Guruvendra.Punugupati@....com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@....com>
---
 drivers/i3c/master/mipi-i3c-hci/core.c       |  4 ++
 drivers/i3c/master/mipi-i3c-hci/hci.h        |  2 +
 drivers/i3c/master/mipi-i3c-hci/hci_quirks.c | 41 ++++++++++++++++++++
 3 files changed, 47 insertions(+)
 create mode 100644 drivers/i3c/master/mipi-i3c-hci/hci_quirks.c

diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
index ae5b1a144506..9fc142ca7532 100644
--- a/drivers/i3c/master/mipi-i3c-hci/core.c
+++ b/drivers/i3c/master/mipi-i3c-hci/core.c
@@ -784,6 +784,10 @@ static int i3c_hci_init(struct i3c_hci *hci)
 		return ret;
 	}
 
+	/* Configure OD and PP timings for AMD platforms */
+	if (hci->quirks & HCI_QUIRK_AMD_OD_PP_TIMING)
+		amd_set_od_pp_timing(hci);
+
 	return 0;
 }
 
diff --git a/drivers/i3c/master/mipi-i3c-hci/hci.h b/drivers/i3c/master/mipi-i3c-hci/hci.h
index 56361adbcc14..f4ec6dcb2ecf 100644
--- a/drivers/i3c/master/mipi-i3c-hci/hci.h
+++ b/drivers/i3c/master/mipi-i3c-hci/hci.h
@@ -140,6 +140,7 @@ struct i3c_hci_dev_data {
 /* list of quirks */
 #define HCI_QUIRK_RAW_CCC	BIT(1)	/* CCC framing must be explicit */
 #define HCI_QUIRK_AMD_PIO_MODE		BIT(2)  /* Set PIO mode for AMD platforms */
+#define HCI_QUIRK_AMD_OD_PP_TIMING	BIT(3)	/* Set OD and PP timings for AMD platforms */
 
 
 /* global functions */
@@ -148,5 +149,6 @@ void mipi_i3c_hci_pio_reset(struct i3c_hci *hci);
 void mipi_i3c_hci_dct_index_reset(struct i3c_hci *hci);
 
 void amd_i3c_hci_quirks_init(struct i3c_hci *hci);
+void amd_set_od_pp_timing(struct i3c_hci *hci);
 
 #endif
diff --git a/drivers/i3c/master/mipi-i3c-hci/hci_quirks.c b/drivers/i3c/master/mipi-i3c-hci/hci_quirks.c
new file mode 100644
index 000000000000..9d8c5eedc8cc
--- /dev/null
+++ b/drivers/i3c/master/mipi-i3c-hci/hci_quirks.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AMD SOC I3C HCI quirks
+ *
+ * Copyright 2024 Advanced Micro Devices, Inc.
+ *
+ * Authors: Shyam Sundar S K <Shyam-sundar.S-k@....com>
+ *          Guruvendra Punugupati <Guruvendra.Punugupati@....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_i3c_hci_quirks_init(struct i3c_hci *hci)
+{
+	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
+		hci->quirks |= HCI_QUIRK_AMD_PIO_MODE;
+		hci->quirks |= HCI_QUIRK_AMD_OD_PP_TIMING;
+	}
+}
+
+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);
+}
-- 
2.25.1