[PATCH 1/7] x86/platform/intel/iosf_mbi: Add a mutex for punit access

From: Hans de Goede <hdegoede@redhat.com>
To: "Daniel Vetter" <daniel.vetter@intel.com>,
	"Jani Nikula" <jani.nikula@linux.intel.com>,
	"Ville Syrjälä" <ville.syrjala@linux.intel.com>,
	"Jarkko Nikula" <jarkko.nikula@linux.intel.com>,
	"Wolfram Sang" <wsa@the-dreams.de>, "Len Brown" <lenb@kernel.org>,
	"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>
Cc: Hans de Goede <hdegoede@redhat.com>,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	dri-devel@lists.freedesktop.org,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Takashi Iwai <tiwai@suse.de>,
	"russianneuromancer @ ya . ru" <russianneuromancer@ya.ru>,
	linux-i2c@vger.kernel.org
Subject: [PATCH 1/7] x86/platform/intel/iosf_mbi: Add a mutex for punit access
Date: Sun,  8 Jan 2017 14:44:21 +0100	[thread overview]
Message-ID: <20170108134427.8392-2-hdegoede@redhat.com> (raw)
In-Reply-To: <20170108134427.8392-1-hdegoede@redhat.com>

One some systems the punit accesses the pmic to change various voltages
through the same bus as other kernel drivers use for e.g. battery
monitoring.

If a driver sends requests to the punit which require the punit to access
the pmic bus while another driver is also accessing the pmic bus various
bad things happen.

This commit adds a mutex to protect the punit against simultaneous accesses
and 2 functions to lock / unlock this mutex.

Note on these systems the i2c-bus driver will request a sempahore from the
punit for exclusive access to the pmic bus when i2c drivers are accessing
it, but this does not appear to be sufficient, we still need to avoid
making certain punit requests during the access window to avoid problems.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=155241
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: tagorereddy <tagore.chandan@gmail.com>
---
 arch/x86/include/asm/iosf_mbi.h    | 31 +++++++++++++++++++++++++++++++
 arch/x86/platform/intel/iosf_mbi.c | 13 +++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/arch/x86/include/asm/iosf_mbi.h b/arch/x86/include/asm/iosf_mbi.h
index b41ee16..91f5d16 100644
--- a/arch/x86/include/asm/iosf_mbi.h
+++ b/arch/x86/include/asm/iosf_mbi.h
@@ -88,6 +88,33 @@ int iosf_mbi_write(u8 port, u8 opcode, u32 offset, u32 mdr);
  */
 int iosf_mbi_modify(u8 port, u8 opcode, u32 offset, u32 mdr, u32 mask);
 
+/**
+ * iosf_mbi_punit_lock() - Lock the punit mutex
+ *
+ * One some systems the punit accesses the pmic to change various voltages
+ * through the same bus as other kernel drivers use for e.g. battery monitoring.
+ *
+ * If a driver sends requests to the punit which require the punit to access the
+ * pmic bus while another driver is also accessing the pmic bus various bad
+ * things happen.
+ *
+ * To avoid these problems this function must be called before accessing the
+ * punit or the pmic, be it through iosf_mbi* functions or through other means.
+ *
+ * Note on these systems the i2c-bus driver will request a sempahore from the
+ * punit for exclusive access to the pmic bus when i2c drivers are accessing it,
+ * but this does not appear to be sufficient, we still need to avoid making
+ * certain punit requests during the access window to avoid problems.
+ *
+ * This function locks a mutex, as such it may sleep.
+ */
+void iosf_mbi_punit_lock(void);
+
+/**
+ * iosf_mbi_punit_unlock() - Unlock the punit mutex
+ */
+void iosf_mbi_punit_unlock(void);
+
 #else /* CONFIG_IOSF_MBI is not enabled */
 static inline
 bool iosf_mbi_available(void)
@@ -115,6 +142,10 @@ int iosf_mbi_modify(u8 port, u8 opcode, u32 offset, u32 mdr, u32 mask)
 	WARN(1, "IOSF_MBI driver not available");
 	return -EPERM;
 }
+
+static inline void iosf_mbi_punit_lock(void) {}
+static inline void iosf_mbi_punit_unlock(void) {}
+
 #endif /* CONFIG_IOSF_MBI */
 
 #endif /* IOSF_MBI_SYMS_H */
diff --git a/arch/x86/platform/intel/iosf_mbi.c b/arch/x86/platform/intel/iosf_mbi.c
index edf2c54..75d8135 100644
--- a/arch/x86/platform/intel/iosf_mbi.c
+++ b/arch/x86/platform/intel/iosf_mbi.c
@@ -34,6 +34,7 @@
 
 static struct pci_dev *mbi_pdev;
 static DEFINE_SPINLOCK(iosf_mbi_lock);
+static DEFINE_MUTEX(iosf_mbi_punit_mutex);
 
 static inline u32 iosf_mbi_form_mcr(u8 op, u8 port, u8 offset)
 {
@@ -190,6 +191,18 @@ bool iosf_mbi_available(void)
 }
 EXPORT_SYMBOL(iosf_mbi_available);
 
+void iosf_mbi_punit_lock(void)
+{
+	mutex_lock(&iosf_mbi_punit_mutex);
+}
+EXPORT_SYMBOL(iosf_mbi_punit_lock);
+
+void iosf_mbi_punit_unlock(void)
+{
+	mutex_unlock(&iosf_mbi_punit_mutex);
+}
+EXPORT_SYMBOL(iosf_mbi_punit_unlock);
+
 #ifdef CONFIG_IOSF_MBI_DEBUG
 static u32	dbg_mdr;
 static u32	dbg_mcr;
-- 
2.9.3
