[PATCH v6] drm: bridge/dw_hdmi: add dw hdmi i2c bus adapter support

[Rob Herring]

On Wed, Aug 24, 2016 at 08:46:37AM +0300, Vladimir Zapolskiy wrote:
> The change adds support of internal HDMI I2C master controller, this
> subdevice is used by default, if "ddc-i2c-bus" DT property is omitted.
> 
> The main purpose of this functionality is to support reading EDID from
> an HDMI monitor on boards, which don't have an I2C bus connected to
> DDC pins.
> 
> The current implementation does not support "I2C Master Interface
> Extended Read Mode" to read data addressed by non-zero segment
> pointer, this means that if EDID has more than 1 extension blocks,
> EDID reading operation won't succeed, in my practice all tested HDMI
> monitors have at maximum one extension block.
> 
> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy at mentor.com>
> ---
> The change is based on top of v4.8.0-rc1 and a fix in DW HDMI driver
> https://patchwork.kernel.org/patch/9284717/
> 
> Changes from v5 to v6:
> * rebased on top of v4.8.0-rc1
> * fixed one improper resource deallocation on error path of dw_hdmi_bind()
> * added a comment describing a mutex asked by checkpatch.pl --strict
> 
> Link to version v5: https://patchwork.kernel.org/patch/7279831/
> 
> Changes from v4 to v5:
> * do I2C bus controller initialization only once in bind() as it was done
>   in v1-v3 of the change.
> 
> Changes from v3 to v4, thanks to Doug and Philipp for review:
> * set speed mode after software reset in dw_hdmi_i2c_init()
> * by default set standard speed mode instead of fast speed mode, on iMX6Q
>   this configures SCL to 100 KHz, which is compliant with HDMI 1.3a spec
> * do I2C bus controller reinitialization on every data transfer,
>   this change hopefully solves some observed problems on RK3288 platform
> * added short functional change description to dw_hdmi.txt
> 
> v3 of the change was
> 
>   Tested-by: Philipp Zabel <p.zabel at pengutronix.de>
> 
> Changes from v2 to v3, thanks to Russell:
> * moved register field value definitions to dw_hdmi.h
> * made completions uninterruptible to avoid transfer retries if interrupted
> * use one completion for both read and write transfers as in v1,
>   operation_reg is removed
> * redundant i2c->stat = 0 is removed from dw_hdmi_i2c_read/write()
> * struct i2c_algorithm dw_hdmi_algorithm is qualified as const
> * dw_hdmi_i2c_adapter() does not modify struct dw_hdmi on error path
> * dw_hdmi_i2c_irq() does not modify hdmi->i2c->stat, if interrupt is
>   not for I2CM
> * spin lock is removed from dw_hdmi_i2c_irq()
> * removed spin lock from dw_hdmi_i2c_xfer() around write to
>   HDMI_IH_MUTE_I2CM_STAT0 register
> * split loop over message array in dw_hdmi_i2c_xfer() to validation
>   and transfer parts
> * added a mutex to serialize I2C transfer requests, i2c->lock is
>   completely removed
> * removed if(len) check from dw_hdmi_i2c_write(), hardware supports
>   only len>0 transfers
> * described extension blocks <= 1 limitation in the commit message
> * a number of minor clean ups
> 
> Changes from v1 to v2:
> * fixed a devm_kfree() signature
> * split completions for read and write operations
> 
>  .../devicetree/bindings/display/bridge/dw_hdmi.txt |   4 +-

Acked-by: Rob Herring <robh at kernel.org>

>  drivers/gpu/drm/bridge/dw-hdmi.c                   | 265 ++++++++++++++++++++-
>  drivers/gpu/drm/bridge/dw-hdmi.h                   |  19 ++
>  3 files changed, 281 insertions(+), 7 deletions(-)