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Date:   Fri, 20 Sep 2019 07:28:59 -0400
From:   Brian Masney <masneyb@onstation.org>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     a.hajda@samsung.com, narmstrong@baylibre.com, jonas@kwiboo.se,
        jernej.skrabec@siol.net, airlied@linux.ie, daniel@ffwll.ch,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        enric.balletbo@collabora.com
Subject: Re: [PATCH v2] drm/bridge: analogix-anx78xx: add support for 7808
 addresses
Message-ID: <20190920112859.GA32015@onstation.org>
References: <20190920101438.6912-1-masneyb@onstation.org>
 <20190920104945.GC12950@pendragon.ideasonboard.com>
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On Fri, Sep 20, 2019 at 01:49:45PM +0300, Laurent Pinchart wrote:
> Hi Brian,
> 
> Thank you for the patch.
> 
> On Fri, Sep 20, 2019 at 06:14:38AM -0400, Brian Masney wrote:
> > According to the downstream Android sources, the anx7808 variants use
> > address 0x78 for TX_P0 and the anx781x variants use address 0x70. Since
> > the datasheets aren't available for these devices, and we only have the
> > downstream kernel sources to look at, let's assume that these addresses
> > are fixed based on the model, and pass the i2c addresses to the data
> > pointer in the driver's of_match_table.
> > 
> > Signed-off-by: Brian Masney <masneyb@onstation.org>
> > ---
> > V1 of this patch with some discussion:
> > https://lore.kernel.org/lkml/20190815004854.19860-6-masneyb@onstation.org/
> > 
> >  drivers/gpu/drm/bridge/analogix-anx78xx.c | 36 +++++++++++++++--------
> >  drivers/gpu/drm/bridge/analogix-anx78xx.h |  7 -----
> >  2 files changed, 23 insertions(+), 20 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/bridge/analogix-anx78xx.c b/drivers/gpu/drm/bridge/analogix-anx78xx.c
> > index 48adf010816c..e25fae36dbe1 100644
> > --- a/drivers/gpu/drm/bridge/analogix-anx78xx.c
> > +++ b/drivers/gpu/drm/bridge/analogix-anx78xx.c
> > @@ -38,12 +38,20 @@
> >  #define AUX_CH_BUFFER_SIZE	16
> >  #define AUX_WAIT_TIMEOUT_MS	15
> >  
> > -static const u8 anx78xx_i2c_addresses[] = {
> > -	[I2C_IDX_TX_P0] = TX_P0,
> > -	[I2C_IDX_TX_P1] = TX_P1,
> > -	[I2C_IDX_TX_P2] = TX_P2,
> > -	[I2C_IDX_RX_P0] = RX_P0,
> > -	[I2C_IDX_RX_P1] = RX_P1,
> > +static const u8 anx7808_i2c_addresses[] = {
> > +	[I2C_IDX_TX_P0] = 0x78,
> > +	[I2C_IDX_TX_P1] = 0x7a,
> > +	[I2C_IDX_TX_P2] = 0x72,
> > +	[I2C_IDX_RX_P0] = 0x7e,
> > +	[I2C_IDX_RX_P1] = 0x80,
> > +};
> > +
> > +static const u8 anx781x_i2c_addresses[] = {
> > +	[I2C_IDX_TX_P0] = 0x70,
> > +	[I2C_IDX_TX_P1] = 0x7a,
> > +	[I2C_IDX_TX_P2] = 0x72,
> > +	[I2C_IDX_RX_P0] = 0x7e,
> > +	[I2C_IDX_RX_P1] = 0x80,
> >  };
> 
> If those addresses are really fixed they should have been added to DT,
> in order for all fixed I2C addresses used on an I2C bus to be reported
> in DT. I guess it's too late now :-/ This seems to be the best we can do
> to solve the problem with existing DT. Updating the bindings could
> however still be a good idea to make this clear moving forward.

One thing to be aware of is that these addresses are actually divided by
two in order to get the real i2c address.

https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/bridge/analogix-anx78xx.c#L1353

I'm not sure why the addresses are represented this way but downstream
does this as well. If I recall correctly, 0x77 is the maximum i2c
address on a bus, and there's a 0x80 above.

> 
> >  struct anx78xx_platform_data {
> > @@ -1348,6 +1356,7 @@ static int anx78xx_i2c_probe(struct i2c_client *client,
> >  	struct anx78xx *anx78xx;
> >  	struct anx78xx_platform_data *pdata;
> >  	unsigned int i, idl, idh, version;
> > +	const u8 *i2c_addresses;
> >  	bool found = false;
> >  	int err;
> >  
> > @@ -1387,15 +1396,16 @@ static int anx78xx_i2c_probe(struct i2c_client *client,
> >  	}
> >  
> >  	/* Map slave addresses of ANX7814 */
> > +	i2c_addresses = device_get_match_data(&client->dev);
> >  	for (i = 0; i < I2C_NUM_ADDRESSES; i++) {
> >  		struct i2c_client *i2c_dummy;
> >  
> >  		i2c_dummy = i2c_new_dummy_device(client->adapter,
> > -						 anx78xx_i2c_addresses[i] >> 1);
> > +						 i2c_addresses[i] >> 1);
> >  		if (IS_ERR(i2c_dummy)) {
> >  			err = PTR_ERR(i2c_dummy);
> >  			DRM_ERROR("Failed to reserve I2C bus %02x: %d\n",
> > -				  anx78xx_i2c_addresses[i], err);
> > +				  i2c_addresses[i], err);
> >  			goto err_unregister_i2c;
> >  		}
> >  
> > @@ -1405,7 +1415,7 @@ static int anx78xx_i2c_probe(struct i2c_client *client,
> >  		if (IS_ERR(anx78xx->map[i])) {
> >  			err = PTR_ERR(anx78xx->map[i]);
> >  			DRM_ERROR("Failed regmap initialization %02x\n",
> > -				  anx78xx_i2c_addresses[i]);
> > +				  i2c_addresses[i]);
> >  			goto err_unregister_i2c;
> >  		}
> >  	}
> > @@ -1504,10 +1514,10 @@ MODULE_DEVICE_TABLE(i2c, anx78xx_id);
> >  
> >  #if IS_ENABLED(CONFIG_OF)
> >  static const struct of_device_id anx78xx_match_table[] = {
> > -	{ .compatible = "analogix,anx7808", },
> > -	{ .compatible = "analogix,anx7812", },
> > -	{ .compatible = "analogix,anx7814", },
> > -	{ .compatible = "analogix,anx7818", },
> > +	{ .compatible = "analogix,anx7808", .data = anx7808_i2c_addresses },
> > +	{ .compatible = "analogix,anx7812", .data = anx781x_i2c_addresses },
> > +	{ .compatible = "analogix,anx7814", .data = anx781x_i2c_addresses },
> > +	{ .compatible = "analogix,anx7818", .data = anx781x_i2c_addresses },
> >  	{ /* sentinel */ },
> >  };
> >  MODULE_DEVICE_TABLE(of, anx78xx_match_table);
> > diff --git a/drivers/gpu/drm/bridge/analogix-anx78xx.h b/drivers/gpu/drm/bridge/analogix-anx78xx.h
> > index 25e063bcecbc..8697647709f7 100644
> > --- a/drivers/gpu/drm/bridge/analogix-anx78xx.h
> > +++ b/drivers/gpu/drm/bridge/analogix-anx78xx.h
> > @@ -6,13 +6,6 @@
> >  #ifndef __ANX78xx_H
> >  #define __ANX78xx_H
> >  
> > -#define TX_P0				0x70
> > -#define TX_P1				0x7a
> > -#define TX_P2				0x72
> > -
> > -#define RX_P0				0x7e
> > -#define RX_P1				0x80
> > -
> >  /***************************************************************/
> >  /* Register definition of device address 0x7e                  */
> >  /***************************************************************/
> 
> Should you also rename the headers to mention [RT]X P[012] instead of
> the numerical addresses ?

Have #defines for ANX781X_TX_P0, ANX7808_TX_P0, etc in the header file?

> 
> Apart from that,
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Thanks,

Brian