[RFC v4 2/8] platform/x86: intel_pmc_ipc: Use spin_lock to protect GCR updates

[sathyanarayanan . kuppuswamy]

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppusw...@linux.intel.com>

Currently, update_no_reboot_bit() function implemented in this driver
uses mutex_lock() to protect its register updates. But this function is
called with in atomic context in iTCO_wdt_start() and iTCO_wdt_stop()
functions in iTCO_wdt.c driver, which in turn causes "sleeping into
atomic context" issue. This patch fixes this issue by replacing the
mutex_lock() with spin_lock() to protect the GCR read/write/update APIs.

Fixes: 9d855d4 ("platform/x86: intel_pmc_ipc: Fix iTCO_wdt GCS memory
mapping failure")
Signed-off-by: Kuppuswamy Sathyanarayanan 
<sathyanarayanan.kuppusw...@linux.intel.com>
---
 drivers/platform/x86/intel_pmc_ipc.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/platform/x86/intel_pmc_ipc.c 
b/drivers/platform/x86/intel_pmc_ipc.c
index c85351e..c68f6a4 100644
--- a/drivers/platform/x86/intel_pmc_ipc.c
+++ b/drivers/platform/x86/intel_pmc_ipc.c
@@ -34,6 +34,7 @@
 #include <linux/acpi.h>
 #include <linux/io-64-nonatomic-lo-hi.h>
 #include <linux/mfd/core.h>
+#include <linux/spinlock.h>
 
 #include <asm/intel_pmc_ipc.h>
 
@@ -126,6 +127,7 @@ static struct intel_pmc_ipc_dev {
        /* gcr */
        void __iomem *gcr_mem_base;
        bool has_gcr_regs;
+       spinlock_t gcr_lock;
 } ipcdev;
 
 static char *ipc_err_sources[] = {
@@ -209,17 +211,17 @@ int intel_pmc_gcr_read(u32 offset, u32 *data)
 {
        int ret;
 
-       mutex_lock(&ipclock);
+       spin_lock(&ipcdev.gcr_lock);
 
        ret = is_gcr_valid(offset);
        if (ret < 0) {
-               mutex_unlock(&ipclock);
+               spin_unlock(&ipcdev.gcr_lock);
                return ret;
        }
 
        *data = readl(ipcdev.gcr_mem_base + offset);
 
-       mutex_unlock(&ipclock);
+       spin_unlock(&ipcdev.gcr_lock);
 
        return 0;
 }
@@ -239,17 +241,17 @@ int intel_pmc_gcr_write(u32 offset, u32 data)
 {
        int ret;
 
-       mutex_lock(&ipclock);
+       spin_lock(&ipcdev.gcr_lock);
 
        ret = is_gcr_valid(offset);
        if (ret < 0) {
-               mutex_unlock(&ipclock);
+               spin_unlock(&ipcdev.gcr_lock);
                return ret;
        }
 
        writel(data, ipcdev.gcr_mem_base + offset);
 
-       mutex_unlock(&ipclock);
+       spin_unlock(&ipcdev.gcr_lock);
 
        return 0;
 }
@@ -271,7 +273,7 @@ int intel_pmc_gcr_update(u32 offset, u32 mask, u32 val)
        u32 new_val;
        int ret = 0;
 
-       mutex_lock(&ipclock);
+       spin_lock(&ipcdev.gcr_lock);
 
        ret = is_gcr_valid(offset);
        if (ret < 0)
@@ -293,7 +295,7 @@ int intel_pmc_gcr_update(u32 offset, u32 mask, u32 val)
        }
 
 gcr_ipc_unlock:
-       mutex_unlock(&ipclock);
+       spin_unlock(&ipcdev.gcr_lock);
        return ret;
 }
 EXPORT_SYMBOL_GPL(intel_pmc_gcr_update);
@@ -471,6 +473,8 @@ static int ipc_pci_probe(struct pci_dev *pdev, const struct 
pci_device_id *id)
        if (pmc->dev)
                return -EBUSY;
 
+       spin_lock_init(&ipcdev.gcr_lock);
+
        pmc->irq_mode = IPC_TRIGGER_MODE_IRQ;
 
        ret = pcim_enable_device(pdev);
@@ -794,6 +798,7 @@ static int ipc_plat_probe(struct platform_device *pdev)
        ipcdev.dev = &pdev->dev;
        ipcdev.irq_mode = IPC_TRIGGER_MODE_IRQ;
        init_completion(&ipcdev.cmd_complete);
+       spin_lock_init(&ipcdev.gcr_lock);
 
        ipcdev.irq = platform_get_irq(pdev, 0);
        if (ipcdev.irq < 0) {
-- 
2.7.4