From mboxrd@z Thu Jan  1 00:00:00 1970
From: Yadi Hu <yadi.hu@windriver.com>
Subject: RESEND:i2c-eg20t: fix race between i2c init and interrupt enable
Date: Wed, 7 Sep 2016 17:25:36 +0800
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the eg20t driver call request_irq() function before the pch_base_address,
base address of i2c controller's register, isassigned an effective value.

it is one possible scenario that an interrupt which isn't inside eg20t
arrives immediately after request_irq() is executed when i2c controller
shares an interrupt number with others.  since the interrupt handler
pch_i2c_handler() has already active as shared action, it will be called
and read its own register to determine if this interrupt is from itself.

At that moment, since base address of i2c registers is not remapped
in kernel space yet,so the INT handler will access an illegal address
and then a error occurs.

Bad IO access at port 0x18 (return inl(port))
 Call Trace:
  [<c102c733>] warn_slowpath_common+0x73/0xa0
  [<c13109f5>] ? bad_io_access+0x45/0x50
  [<c13109f5>] ? bad_io_access+0x45/0x50
  [<c102c804>] warn_slowpath_fmt+0x34/0x40
  [<c13109f5>] bad_io_access+0x45/0x50
  [<c1310b62>] ioread32+0x22/0x40
  [<c14c60db>] pch_i2c_handler+0x3b/0x120
  [<c1092f34>] handle_irq_event_percpu+0x64/0x330
  [<c109323b>] handle_irq_event+0x3b/0x60
  [<c1095b50>] ? unmask_irq+0x30/0x30
  [<c1095ba0>] handle_fasteoi_irq+0x50/0xe0
  <IRQ>  [<c16e7e78>] ? do_IRQ+0x48/0xc0
  [<c16e7f6f>] ? smp_apic_timer_interrupt+0x7f/0x17a
  [<c16e7da9>] ? common_interrupt+0x29/0x30
  [<c1008ebb>] ? mwait_idle+0x8b/0x2c0
  [<c1009e8e>] ? cpu_idle+0x9e/0xc0
  [<c16be408>] ? rest_init+0x6c/0x74
  [<c19f770a>] ? start_kernel+0x311/0x318
  [<c19f7231>] ? repair_env_string+0x51/0x51
  [<c19f7078>] ? i386_start_kernel+0x78/0x7d
 ---[ end trace eb3a1028f468a140 ]---
 i2c_eg20t 0000:05:0c.2: pch_i2c_handler :I2C-3 mode(0) is not supported

after testing last patch, replacing request_irq() location is not a
good idea,it might produce a little time windows ,in which the interrupts
occurring inside  will be omitted.

the new patch adds a check point on interrupt handler in case field
'pch_base_address' has not been initialed.


Yadi Hu (1)
    i2c-eg20t: fix race between i2c init and interrupt enable

drivers/i2c/busses/i2c-eg20t.c |    5 +++++
 1 file changed, 5 insertions(+)