linux-kernel - Re: [PATCH] drm: adv7511: override i2c address of cec before accessing it

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Message-ID: <164001209406.2512616.469307346369770543@Monstersaurus>
Date:   Mon, 20 Dec 2021 14:54:54 +0000
From:   Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
To:     Andrzej Hajda <a.hajda@...sung.com>,
        Antonio Borneo <antonio.borneo@...s.st.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        dri-devel@...ts.freedesktop.org
Cc:     Antonio Borneo <antonio.borneo@...s.st.com>,
        linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH] drm: adv7511: override i2c address of cec before accessing it

Hi Antonio,

Quoting Antonio Borneo (2021-12-18 18:28:04)
> Commit 680532c50bca ("drm: adv7511: Add support for
> i2c_new_secondary_device") allows a device tree node to override
> the default addresses of the secondary i2c devices. This is useful
> for solving address conflicts on the i2c bus.
> 
> In adv7511_init_cec_regmap() the new i2c address of cec device is
> read from device tree and immediately accessed, well before it is
> written in the proper register to override the default address.
> This can cause an i2c error during probe and a consequent probe
> failure.

Ouch, it does seem that way. I guess no one has used the CEC for quite
some time, as it must have been like this for a while?

> Once the new i2c address is read from the device tree, override
> the default address before any attempt to access the cec.

Reviewed-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>

> Tested with adv7533 and stm32mp157f.
> 
> Signed-off-by: Antonio Borneo <antonio.borneo@...s.st.com>
> Fixes: 680532c50bca ("drm: adv7511: Add support for i2c_new_secondary_device")
> ---
> To: Andrzej Hajda <a.hajda@...sung.com>
> To: Neil Armstrong <narmstrong@...libre.com>
> To: Robert Foss <robert.foss@...aro.org>
> To: Laurent Pinchart <Laurent.pinchart@...asonboard.com>
> To: Jonas Karlman <jonas@...boo.se>
> To: Jernej Skrabec <jernej.skrabec@...il.com>
> To: David Airlie <airlied@...ux.ie>
> To: Daniel Vetter <daniel@...ll.ch>
> To: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> To: dri-devel@...ts.freedesktop.org
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-stm32@...md-mailman.stormreply.com
> ---
>  drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> index 76555ae64e9c..629e05286fd9 100644
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> @@ -1048,6 +1048,10 @@ static int adv7511_init_cec_regmap(struct adv7511 *adv)
>                                                 ADV7511_CEC_I2C_ADDR_DEFAULT);
>         if (IS_ERR(adv->i2c_cec))
>                 return PTR_ERR(adv->i2c_cec);
> +
> +       regmap_write(adv->regmap, ADV7511_REG_CEC_I2C_ADDR,
> +                    adv->i2c_cec->addr << 1);
> +
>         i2c_set_clientdata(adv->i2c_cec, adv);
>  
>         adv->regmap_cec = devm_regmap_init_i2c(adv->i2c_cec,
> @@ -1252,9 +1256,6 @@ static int adv7511_probe(struct i2c_client *i2c, const struct i2c_device_id *id)
>         if (ret)
>                 goto err_i2c_unregister_packet;
>  
> -       regmap_write(adv7511->regmap, ADV7511_REG_CEC_I2C_ADDR,
> -                    adv7511->i2c_cec->addr << 1);
> -
>         INIT_WORK(&adv7511->hpd_work, adv7511_hpd_work);
>  
>         if (i2c->irq) {
> 
> base-commit: fc74881c28d314b10efac016ef49df4ff40b8b97
> -- 
> 2.34.1
>