• Dmitry Osipenko's avatar
    i2c: tegra: Support atomic transfers · ede2299f
    Dmitry Osipenko authored
    
    
    System shutdown may happen with interrupts being disabled and in this case
    kernel may hang if atomic transfer isn't supported by driver.
    
    There were several occurrences where I found my Nexus 7 completely
    discharged despite of being turned off and then one day I spotted this in
    the log:
    
     reboot: Power down
     ------------[ cut here ]------------
     WARNING: CPU: 0 PID: 1 at drivers/i2c/i2c-core.h:40 i2c_transfer+0x95/0x9c
     No atomic I2C transfer handler for 'i2c-1'
     Modules linked in: tegra30_devfreq
     CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted 5.4.0-next-20191202-00120-gf7ecd80fb803-dirty #3195
     Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
     [<c010e4b5>] (unwind_backtrace) from [<c010a0fd>] (show_stack+0x11/0x14)
     [<c010a0fd>] (show_stack) from [<c09995e5>] (dump_stack+0x85/0x94)
     [<c09995e5>] (dump_stack) from [<c011f3d1>] (__warn+0xc1/0xc4)
     [<c011f3d1>] (__warn) from [<c011f691>] (warn_slowpath_fmt+0x61/0x78)
     [<c011f691>] (warn_slowpath_fmt) from [<c069a8dd>] (i2c_transfer+0x95/0x9c)
     [<c069a8dd>] (i2c_transfer) from [<c05667f1>] (regmap_i2c_read+0x4d/0x6c)
     [<c05667f1>] (regmap_i2c_read) from [<c0563601>] (_regmap_raw_read+0x99/0x1cc)
     [<c0563601>] (_regmap_raw_read) from [<c0563757>] (_regmap_bus_read+0x23/0x38)
     [<c0563757>] (_regmap_bus_read) from [<c056293d>] (_regmap_read+0x3d/0xfc)
     [<c056293d>] (_regmap_read) from [<c0562d3b>] (_regmap_update_bits+0x87/0xc4)
     [<c0562d3b>] (_regmap_update_bits) from [<c0563add>] (regmap_update_bits_base+0x39/0x50)
     [<c0563add>] (regmap_update_bits_base) from [<c056fd39>] (max77620_pm_power_off+0x29/0x2c)
     [<c056fd39>] (max77620_pm_power_off) from [<c013bbdd>] (__do_sys_reboot+0xe9/0x170)
     [<c013bbdd>] (__do_sys_reboot) from [<c0101001>] (ret_fast_syscall+0x1/0x28)
     Exception stack(0xde907fa8 to 0xde907ff0)
     7fa0:                   00000000 00000000 fee1dead 28121969 4321fedc 00000000
     7fc0: 00000000 00000000 00000000 00000058 00000000 00000000 00000000 00000000
     7fe0: 0045adf0 bed9abb8 004444a0 b6c666d0
     ---[ end trace bdd18f87595b1a5e ]---
    
    The atomic transferring is implemented by enforcing PIO mode for the
    transfer and by polling interrupt status until transfer is completed or
    failed.
    
    Now system shuts down properly every time.
    
    Tested-by: default avatarThierry Reding <treding@nvidia.com>
    Signed-off-by: default avatarDmitry Osipenko <digetx@gmail.com>
    Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
    ede2299f