[PATCH v1] powerpc: low_i2c: change @lock to raw_spinlock_t

[John Ogness]

i2c transfers are occurring with local interrupts disabled:

smp_core99_give_timebase()
  local_irq_save();
  smp_core99_cypress_tb_freeze()
    pmac_i2c_xfer()
      kw_i2c_xfer()
        spin_lock_irqsave(&host->lock, flags)

This is a problem because with PREEMPT_RT a spinlock_t can sleep,
causing the system to hang. Convert the spinlock_t to the
non-sleeping raw_spinlock_t.

Signed-off-by: John Ogness <john.ogn...@linutronix.de>
---
 arch/powerpc/platforms/powermac/low_i2c.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/platforms/powermac/low_i2c.c 
b/arch/powerpc/platforms/powermac/low_i2c.c
index f77a59b5c2e1..ba89c95ef290 100644
--- a/arch/powerpc/platforms/powermac/low_i2c.c
+++ b/arch/powerpc/platforms/powermac/low_i2c.c
@@ -116,7 +116,7 @@ struct pmac_i2c_host_kw
        int                     polled;
        int                     result;
        struct completion       complete;
-       spinlock_t              lock;
+       raw_spinlock_t          lock;
        struct timer_list       timeout_timer;
 };
 
@@ -346,14 +346,14 @@ static irqreturn_t kw_i2c_irq(int irq, void *dev_id)
        struct pmac_i2c_host_kw *host = dev_id;
        unsigned long flags;
 
-       spin_lock_irqsave(&host->lock, flags);
+       raw_spin_lock_irqsave(&host->lock, flags);
        del_timer(&host->timeout_timer);
        kw_i2c_handle_interrupt(host, kw_read_reg(reg_isr));
        if (host->state != state_idle) {
                host->timeout_timer.expires = jiffies + KW_POLL_TIMEOUT;
                add_timer(&host->timeout_timer);
        }
-       spin_unlock_irqrestore(&host->lock, flags);
+       raw_spin_unlock_irqrestore(&host->lock, flags);
        return IRQ_HANDLED;
 }
 
@@ -362,7 +362,7 @@ static void kw_i2c_timeout(struct timer_list *t)
        struct pmac_i2c_host_kw *host = from_timer(host, t, timeout_timer);
        unsigned long flags;
 
-       spin_lock_irqsave(&host->lock, flags);
+       raw_spin_lock_irqsave(&host->lock, flags);
 
        /*
         * If the timer is pending, that means we raced with the
@@ -377,7 +377,7 @@ static void kw_i2c_timeout(struct timer_list *t)
                add_timer(&host->timeout_timer);
        }
  skip:
-       spin_unlock_irqrestore(&host->lock, flags);
+       raw_spin_unlock_irqrestore(&host->lock, flags);
 }
 
 static int kw_i2c_open(struct pmac_i2c_bus *bus)
@@ -470,9 +470,9 @@ static int kw_i2c_xfer(struct pmac_i2c_bus *bus, u8 
addrdir, int subsize,
                        unsigned long flags;
 
                        u8 isr = kw_i2c_wait_interrupt(host);
-                       spin_lock_irqsave(&host->lock, flags);
+                       raw_spin_lock_irqsave(&host->lock, flags);
                        kw_i2c_handle_interrupt(host, isr);
-                       spin_unlock_irqrestore(&host->lock, flags);
+                       raw_spin_unlock_irqrestore(&host->lock, flags);
                }
        }
 
@@ -508,7 +508,7 @@ static struct pmac_i2c_host_kw *__init 
kw_i2c_host_init(struct device_node *np)
        }
        mutex_init(&host->mutex);
        init_completion(&host->complete);
-       spin_lock_init(&host->lock);
+       raw_spin_lock_init(&host->lock);
        timer_setup(&host->timeout_timer, kw_i2c_timeout, 0);
 
        psteps = of_get_property(np, "AAPL,address-step", NULL);
-- 
2.20.1