diff mbox series

[1/2] gpio: gpio-mmio: Allow volatile shadow regs

Message ID 20181017213012.233957-2-kunyi@google.com
State Not Applicable, archived
Headers show
Series Allow gpio-mmio to co-exist with pinctrl driver | expand

Commit Message

Kun Yi Oct. 17, 2018, 9:30 p.m. UTC 
Currently the generic GPIO driver stores the direction and data shadow register
when the driver probes. However, in embedded SOCs the GPIO pins are often
interleaved with pins muxed to other functions, and pinctrl driver might
toggle the direction/data register values for these pins. With GPIO
driver being not the only owner, it should read the shadow registers
before updating them, otherwise some pin states would be overwritten.

This patch adds a flag BGPIOF_VOLATILE_REG to allow a pinctrl driver that uses
the generic GPIO interface to indicate the need of read-before-update.

Signed-off-by: Kun Yi <kunyi@google.com>
---
 drivers/gpio/gpio-mmio.c    | 50 +++++++++++++++++++++++++------------
 include/linux/gpio/driver.h |  2 ++
 2 files changed, 36 insertions(+), 16 deletions(-)

Comments

kernel test robot Oct. 18, 2018, 11:49 a.m. UTC | #1 
Hi Kun,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on gpio/for-next]
[also build test WARNING on v4.19-rc8 next-20181018]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Kun-Yi/gpio-gpio-mmio-Allow-volatile-shadow-regs/20181018-144115
base:   https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio.git for-next
reproduce: make htmldocs

All warnings (new ones prefixed by >>):

   WARNING: convert(1) not found, for SVG to PDF conversion install ImageMagick (https://www.imagemagick.org)
   include/linux/srcu.h:175: warning: Function parameter or member 'p' not described in 'srcu_dereference_notrace'
   include/linux/srcu.h:175: warning: Function parameter or member 'sp' not described in 'srcu_dereference_notrace'
   include/linux/gfp.h:1: warning: no structured comments found
   include/net/cfg80211.h:4381: warning: Function parameter or member 'wext.ibss' not described in 'wireless_dev'
   include/net/cfg80211.h:4381: warning: Function parameter or member 'wext.connect' not described in 'wireless_dev'
   include/net/cfg80211.h:4381: warning: Function parameter or member 'wext.keys' not described in 'wireless_dev'
   include/net/cfg80211.h:4381: warning: Function parameter or member 'wext.ie' not described in 'wireless_dev'
   include/net/cfg80211.h:4381: warning: Function parameter or member 'wext.ie_len' not described in 'wireless_dev'
   include/net/cfg80211.h:4381: warning: Function parameter or member 'wext.bssid' not described in 'wireless_dev'
   include/net/cfg80211.h:4381: warning: Function parameter or member 'wext.ssid' not described in 'wireless_dev'
   include/net/cfg80211.h:4381: warning: Function parameter or member 'wext.default_key' not described in 'wireless_dev'
   include/net/cfg80211.h:4381: warning: Function parameter or member 'wext.default_mgmt_key' not described in 'wireless_dev'
   include/net/cfg80211.h:4381: warning: Function parameter or member 'wext.prev_bssid_valid' not described in 'wireless_dev'
   include/net/mac80211.h:2328: warning: Function parameter or member 'radiotap_timestamp.units_pos' not described in 'ieee80211_hw'
   include/net/mac80211.h:2328: warning: Function parameter or member 'radiotap_timestamp.accuracy' not described in 'ieee80211_hw'
   include/net/mac80211.h:977: warning: Function parameter or member 'control.rates' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'control.rts_cts_rate_idx' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'control.use_rts' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'control.use_cts_prot' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'control.short_preamble' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'control.skip_table' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'control.jiffies' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'control.vif' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'control.hw_key' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'control.flags' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'control.enqueue_time' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'ack' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'ack.cookie' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'status.rates' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'status.ack_signal' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'status.ampdu_ack_len' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'status.ampdu_len' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'status.antenna' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'status.tx_time' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'status.is_valid_ack_signal' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'status.status_driver_data' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'driver_rates' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'pad' not described in 'ieee80211_tx_info'
   include/net/mac80211.h:977: warning: Function parameter or member 'rate_driver_data' not described in 'ieee80211_tx_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'rx_stats_avg' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'rx_stats_avg.signal' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'rx_stats_avg.chain_signal' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'status_stats.filtered' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'status_stats.retry_failed' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'status_stats.retry_count' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'status_stats.lost_packets' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'status_stats.last_tdls_pkt_time' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'status_stats.msdu_retries' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'status_stats.msdu_failed' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'status_stats.last_ack' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'status_stats.last_ack_signal' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'status_stats.ack_signal_filled' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'status_stats.avg_ack_signal' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'tx_stats.packets' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'tx_stats.bytes' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'tx_stats.last_rate' not described in 'sta_info'
   net/mac80211/sta_info.h:588: warning: Function parameter or member 'tx_stats.msdu' not described in 'sta_info'
   include/linux/mod_devicetable.h:763: warning: Function parameter or member 'driver_data' not described in 'typec_device_id'
   kernel/sched/fair.c:3371: warning: Function parameter or member 'flags' not described in 'attach_entity_load_avg'
   arch/x86/include/asm/atomic.h:84: warning: Excess function parameter 'i' description in 'arch_atomic_sub_and_test'
   arch/x86/include/asm/atomic.h:84: warning: Excess function parameter 'v' description in 'arch_atomic_sub_and_test'
   arch/x86/include/asm/atomic.h:96: warning: Excess function parameter 'v' description in 'arch_atomic_inc'
   arch/x86/include/asm/atomic.h:109: warning: Excess function parameter 'v' description in 'arch_atomic_dec'
   arch/x86/include/asm/atomic.h:124: warning: Excess function parameter 'v' description in 'arch_atomic_dec_and_test'
   arch/x86/include/asm/atomic.h:138: warning: Excess function parameter 'v' description in 'arch_atomic_inc_and_test'
   arch/x86/include/asm/atomic.h:153: warning: Excess function parameter 'i' description in 'arch_atomic_add_negative'
   arch/x86/include/asm/atomic.h:153: warning: Excess function parameter 'v' description in 'arch_atomic_add_negative'
   include/linux/dma-buf.h:304: warning: Function parameter or member 'cb_excl.cb' not described in 'dma_buf'
   include/linux/dma-buf.h:304: warning: Function parameter or member 'cb_excl.poll' not described in 'dma_buf'
   include/linux/dma-buf.h:304: warning: Function parameter or member 'cb_excl.active' not described in 'dma_buf'
   include/linux/dma-buf.h:304: warning: Function parameter or member 'cb_shared.cb' not described in 'dma_buf'
   include/linux/dma-buf.h:304: warning: Function parameter or member 'cb_shared.poll' not described in 'dma_buf'
   include/linux/dma-buf.h:304: warning: Function parameter or member 'cb_shared.active' not described in 'dma_buf'
   include/linux/dma-fence-array.h:54: warning: Function parameter or member 'work' not described in 'dma_fence_array'
   include/linux/gpio/driver.h:369: warning: Function parameter or member 'init_valid_mask' not described in 'gpio_chip'
>> include/linux/gpio/driver.h:369: warning: Function parameter or member 'bgpio_regs_are_volatile' not described in 'gpio_chip'
   include/linux/iio/hw-consumer.h:1: warning: no structured comments found
   include/linux/input/sparse-keymap.h:46: warning: Function parameter or member 'sw' not described in 'key_entry'
   drivers/pci/pci.c:218: warning: Excess function parameter 'p' description in 'pci_dev_str_match_path'
   include/linux/regulator/driver.h:227: warning: Function parameter or member 'resume' not described in 'regulator_ops'
   drivers/regulator/core.c:4479: warning: Excess function parameter 'state' description in 'regulator_suspend'
   arch/s390/include/asm/cio.h:245: warning: Function parameter or member 'esw.esw0' not described in 'irb'
   arch/s390/include/asm/cio.h:245: warning: Function parameter or member 'esw.esw1' not described in 'irb'
   arch/s390/include/asm/cio.h:245: warning: Function parameter or member 'esw.esw2' not described in 'irb'
   arch/s390/include/asm/cio.h:245: warning: Function parameter or member 'esw.esw3' not described in 'irb'
   arch/s390/include/asm/cio.h:245: warning: Function parameter or member 'esw.eadm' not described in 'irb'
   drivers/slimbus/stream.c:1: warning: no structured comments found
   drivers/target/target_core_device.c:1: warning: no structured comments found
   drivers/usb/dwc3/gadget.c:510: warning: Excess function parameter 'dwc' description in 'dwc3_gadget_start_config'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/bus.c:1: warning: no structured comments found
   drivers/usb/typec/bus.c:268: warning: Function parameter or member 'mode' not described in 'typec_match_altmode'
   drivers/usb/typec/class.c:1497: warning: Excess function parameter 'drvdata' description in 'typec_port_register_altmode'
   drivers/usb/typec/class.c:1: warning: no structured comments found
   include/linux/w1.h:281: warning: Function parameter or member 'of_match_table' not described in 'w1_family'
   fs/direct-io.c:257: warning: Excess function parameter 'offset' description in 'dio_complete'
   fs/file_table.c:1: warning: no structured comments found
   fs/libfs.c:477: warning: Excess function parameter 'available' description in 'simple_write_end'
   fs/posix_acl.c:646: warning: Function parameter or member 'inode' not described in 'posix_acl_update_mode'
   fs/posix_acl.c:646: warning: Function parameter or member 'mode_p' not described in 'posix_acl_update_mode'
   fs/posix_acl.c:646: warning: Function parameter or member 'acl' not described in 'posix_acl_update_mode'
   drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c:183: warning: Function parameter or member 'blockable' not described in 'amdgpu_mn_read_lock'
   drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c:254: warning: Function parameter or member 'blockable' not described in 'amdgpu_mn_invalidate_range_start_gfx'
   drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c:302: warning: Function parameter or member 'blockable' not described in 'amdgpu_mn_invalidate_range_start_hsa'
   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:2986: warning: Excess function parameter 'dev' description in 'amdgpu_vm_get_task_info'
   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:2987: warning: Function parameter or member 'adev' not described in 'amdgpu_vm_get_task_info'
   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:2987: warning: Excess function parameter 'dev' description in 'amdgpu_vm_get_task_info'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_pin' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_unpin' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_res_obj' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_get_sg_table' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_import_sg_table' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_vmap' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_vunmap' not described in 'drm_driver'
   include/drm/drm_drv.h:610: warning: Function parameter or member 'gem_prime_mmap' not described in 'drm_driver'
   include/drm/drm_panel.h:98: warning: Function parameter or member 'link' not described in 'drm_panel'
   drivers/gpu/drm/i915/i915_vma.h:49: warning: cannot understand function prototype: 'struct i915_vma '
   drivers/gpu/drm/i915/i915_vma.h:1: warning: no structured comments found
   drivers/gpu/drm/i915/intel_guc_fwif.h:553: warning: cannot understand function prototype: 'struct guc_log_buffer_state '
   drivers/gpu/drm/i915/i915_trace.h:1: warning: no structured comments found
   include/linux/skbuff.h:860: warning: Function parameter or member 'dev_scratch' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'list' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'ip_defrag_offset' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'skb_mstamp' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member '__cloned_offset' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'head_frag' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member '__pkt_type_offset' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'encapsulation' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'encap_hdr_csum' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'csum_valid' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'csum_complete_sw' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'csum_level' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'inner_protocol_type' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'remcsum_offload' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'offload_fwd_mark' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'offload_mr_fwd_mark' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'sender_cpu' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'reserved_tailroom' not described in 'sk_buff'
   include/linux/skbuff.h:860: warning: Function parameter or member 'inner_ipproto' not described in 'sk_buff'
   include/net/sock.h:238: warning: Function parameter or member 'skc_addrpair' not described in 'sock_common'
   include/net/sock.h:238: warning: Function parameter or member 'skc_portpair' not described in 'sock_common'
   include/net/sock.h:238: warning: Function parameter or member 'skc_ipv6only' not described in 'sock_common'
   include/net/sock.h:238: warning: Function parameter or member 'skc_net_refcnt' not described in 'sock_common'
   include/net/sock.h:238: warning: Function parameter or member 'skc_v6_daddr' not described in 'sock_common'
   include/net/sock.h:238: warning: Function parameter or member 'skc_v6_rcv_saddr' not described in 'sock_common'
   include/net/sock.h:238: warning: Function parameter or member 'skc_cookie' not described in 'sock_common'
   include/net/sock.h:238: warning: Function parameter or member 'skc_listener' not described in 'sock_common'
   include/net/sock.h:238: warning: Function parameter or member 'skc_tw_dr' not described in 'sock_common'
   include/net/sock.h:238: warning: Function parameter or member 'skc_rcv_wnd' not described in 'sock_common'
   include/net/sock.h:238: warning: Function parameter or member 'skc_tw_rcv_nxt' not described in 'sock_common'
   include/net/sock.h:509: warning: Function parameter or member 'sk_backlog.rmem_alloc' not described in 'sock'
   include/net/sock.h:509: warning: Function parameter or member 'sk_backlog.len' not described in 'sock'
   include/net/sock.h:509: warning: Function parameter or member 'sk_backlog.head' not described in 'sock'
   include/net/sock.h:509: warning: Function parameter or member 'sk_backlog.tail' not described in 'sock'
   include/net/sock.h:509: warning: Function parameter or member 'sk_wq_raw' not described in 'sock'
   include/net/sock.h:509: warning: Function parameter or member 'tcp_rtx_queue' not described in 'sock'
   include/net/sock.h:509: warning: Function parameter or member 'sk_route_forced_caps' not described in 'sock'
   include/net/sock.h:509: warning: Function parameter or member 'sk_txtime_report_errors' not described in 'sock'
   include/net/sock.h:509: warning: Function parameter or member 'sk_validate_xmit_skb' not described in 'sock'
   include/linux/netdevice.h:2018: warning: Function parameter or member 'adj_list.upper' not described in 'net_device'
   include/linux/netdevice.h:2018: warning: Function parameter or member 'adj_list.lower' not described in 'net_device'
   include/linux/netdevice.h:2018: warning: Function parameter or member 'gso_partial_features' not described in 'net_device'
   include/linux/netdevice.h:2018: warning: Function parameter or member 'switchdev_ops' not described in 'net_device'
   include/linux/netdevice.h:2018: warning: Function parameter or member 'l3mdev_ops' not described in 'net_device'
   include/linux/netdevice.h:2018: warning: Function parameter or member 'xfrmdev_ops' not described in 'net_device'

vim +369 include/linux/gpio/driver.h

79a9becd Alexandre Courbot 2013-10-17 @369  

:::::: The code at line 369 was first introduced by commit
:::::: 79a9becda8940deb2274b5aa4577c86d52ee7ecb gpiolib: export descriptor-based GPIO interface

:::::: TO: Alexandre Courbot <acourbot@nvidia.com>
:::::: CC: Linus Walleij <linus.walleij@linaro.org>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
Linus Walleij Oct. 30, 2018, 12:06 p.m. UTC | #2 
On Wed, Oct 17, 2018 at 11:30 PM Kun Yi <kunyi@google.com> wrote:

> Currently the generic GPIO driver stores the direction and data shadow register
> when the driver probes. However, in embedded SOCs the GPIO pins are often
> interleaved with pins muxed to other functions, and pinctrl driver might
> toggle the direction/data register values for these pins. With GPIO
> driver being not the only owner, it should read the shadow registers
> before updating them, otherwise some pin states would be overwritten.
>
> This patch adds a flag BGPIOF_VOLATILE_REG to allow a pinctrl driver that uses
> the generic GPIO interface to indicate the need of read-before-update.
>
> Signed-off-by: Kun Yi <kunyi@google.com>

Hi Kun,

as you see the build robot has problems with the patch, please look
into it.

Architecturally I'm not so sure about this, we are introducing more
and more "shadow registers" and I feel what happens at the end
of the day is that we end up reimplementing regmap-mmio.

Please look into switching gpio-mmio.c to use regmap-mmio
and add more registers based on that.

It might be a bit complex but is a way better way forward for
everyone.

Yours,
Linus Walleij
diff mbox series

Patch

diff --git a/drivers/gpio/gpio-mmio.c b/drivers/gpio/gpio-mmio.c
index 935292a30c99..5e13e43a793d 100644
--- a/drivers/gpio/gpio-mmio.c
+++ b/drivers/gpio/gpio-mmio.c
@@ -136,7 +136,12 @@  static unsigned long bgpio_line2mask(struct gpio_chip *gc, unsigned int line)
 static int bgpio_get_set(struct gpio_chip *gc, unsigned int gpio)
 {
 	unsigned long pinmask = bgpio_line2mask(gc, gpio);
-	bool dir = !!(gc->bgpio_dir & pinmask);
+	bool dir;
+
+	if (gc->bgpio_regs_are_volatile)
+		gc->bgpio_dir = gc->read_reg(gc->reg_dir);
+
+	dir = !!(gc->bgpio_dir & pinmask);
 
 	/*
 	 * If the direction is OUT we read the value from the SET
@@ -168,6 +173,9 @@  static int bgpio_get_set_multiple(struct gpio_chip *gc, unsigned long *mask,
 	/* Make sure we first clear any bits that are zero when we read the register */
 	*bits &= ~*mask;
 
+	if (gc->bgpio_regs_are_volatile)
+		gc->bgpio_dir = gc->read_reg(gc->reg_dir);
+
 	/* Exploit the fact that we know which directions are set */
 	if (gc->bgpio_dir_inverted) {
 		set_mask = *mask & ~gc->bgpio_dir;
@@ -238,21 +246,31 @@  static void bgpio_set_none(struct gpio_chip *gc, unsigned int gpio, int val)
 {
 }
 
-static void bgpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
+static void bgpio_set_single_reg(struct gpio_chip *gc, unsigned int gpio,
+				 int val, void __iomem *reg)
 {
 	unsigned long mask = bgpio_line2mask(gc, gpio);
 	unsigned long flags;
 
 	spin_lock_irqsave(&gc->bgpio_lock, flags);
 
+	if (gc->bgpio_regs_are_volatile)
+		gc->bgpio_data = gc->read_reg(reg);
+
 	if (val)
 		gc->bgpio_data |= mask;
 	else
 		gc->bgpio_data &= ~mask;
 
-	gc->write_reg(gc->reg_dat, gc->bgpio_data);
+	gc->write_reg(reg, gc->bgpio_data);
 
 	spin_unlock_irqrestore(&gc->bgpio_lock, flags);
+
+}
+
+static void bgpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
+{
+	bgpio_set_single_reg(gc, gpio, val, gc->reg_dat);
 }
 
 static void bgpio_set_with_clear(struct gpio_chip *gc, unsigned int gpio,
@@ -268,19 +286,7 @@  static void bgpio_set_with_clear(struct gpio_chip *gc, unsigned int gpio,
 
 static void bgpio_set_set(struct gpio_chip *gc, unsigned int gpio, int val)
 {
-	unsigned long mask = bgpio_line2mask(gc, gpio);
-	unsigned long flags;
-
-	spin_lock_irqsave(&gc->bgpio_lock, flags);
-
-	if (val)
-		gc->bgpio_data |= mask;
-	else
-		gc->bgpio_data &= ~mask;
-
-	gc->write_reg(gc->reg_set, gc->bgpio_data);
-
-	spin_unlock_irqrestore(&gc->bgpio_lock, flags);
+	bgpio_set_single_reg(gc, gpio, val, gc->reg_set);
 }
 
 static void bgpio_multiple_get_masks(struct gpio_chip *gc,
@@ -317,6 +323,9 @@  static void bgpio_set_multiple_single_reg(struct gpio_chip *gc,
 
 	bgpio_multiple_get_masks(gc, mask, bits, &set_mask, &clear_mask);
 
+	if (gc->bgpio_regs_are_volatile)
+		gc->bgpio_data = gc->read_reg(reg);
+
 	gc->bgpio_data |= set_mask;
 	gc->bgpio_data &= ~clear_mask;
 
@@ -376,6 +385,9 @@  static int bgpio_dir_in(struct gpio_chip *gc, unsigned int gpio)
 
 	spin_lock_irqsave(&gc->bgpio_lock, flags);
 
+	if (gc->bgpio_regs_are_volatile)
+		gc->bgpio_dir = gc->read_reg(gc->reg_dir);
+
 	if (gc->bgpio_dir_inverted)
 		gc->bgpio_dir |= bgpio_line2mask(gc, gpio);
 	else
@@ -404,6 +416,9 @@  static int bgpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
 
 	spin_lock_irqsave(&gc->bgpio_lock, flags);
 
+	if (gc->bgpio_regs_are_volatile)
+		gc->bgpio_dir = gc->read_reg(gc->reg_dir);
+
 	if (gc->bgpio_dir_inverted)
 		gc->bgpio_dir &= ~bgpio_line2mask(gc, gpio);
 	else
@@ -641,6 +656,9 @@  int bgpio_init(struct gpio_chip *gc, struct device *dev,
 	if (gc->reg_dir && !(flags & BGPIOF_UNREADABLE_REG_DIR))
 		gc->bgpio_dir = gc->read_reg(gc->reg_dir);
 
+	if (flags & BGPIOF_VOLATILE_REG)
+		gc->bgpio_regs_are_volatile = true;
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(bgpio_init);
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 0ea328e71ec9..a889037daf20 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -274,6 +274,7 @@  struct gpio_chip {
 	spinlock_t bgpio_lock;
 	unsigned long bgpio_data;
 	unsigned long bgpio_dir;
+	bool bgpio_regs_are_volatile;
 #endif
 
 #ifdef CONFIG_GPIOLIB_IRQCHIP
@@ -428,6 +429,7 @@  int bgpio_init(struct gpio_chip *gc, struct device *dev,
 #define BGPIOF_BIG_ENDIAN_BYTE_ORDER	BIT(3)
 #define BGPIOF_READ_OUTPUT_REG_SET	BIT(4) /* reg_set stores output value */
 #define BGPIOF_NO_OUTPUT		BIT(5) /* only input */
+#define BGPIOF_VOLATILE_REG		BIT(6) /* update shadow before writing*/
 
 #endif