Re: [PATCH 1/3] drm/bridge/sii8620: perform I2C bus recovery after reset

From: Andrzej Hajda <a.hajda@samsung.com>
To: Archit Taneja <architt@codeaurora.org>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	dri-devel@lists.freedesktop.org,
	linux-samsung-soc@vger.kernel.org
Subject: Re: [PATCH 1/3] drm/bridge/sii8620: perform I2C bus recovery after reset
Date: Fri, 26 Jan 2018 15:05:15 +0100	[thread overview]
Message-ID: <2ae62c14-5182-7837-f446-f6ac5c6ce90f@samsung.com> (raw)
In-Reply-To: <20180115173357.31067-2-a.hajda@samsung.com>

On 15.01.2018 18:33, Andrzej Hajda wrote:
> Chip has known bug which causes I2C client state machine to frequently
> enter non-idle mode after chip reset. Let's ask I2C adapter to perform
> bus recovery to mitigate this bug.
>
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
> ---
>  drivers/gpu/drm/bridge/sil-sii8620.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/sil-sii8620.c b/drivers/gpu/drm/bridge/sil-sii8620.c
> index 86789f8918a4..db93e5e0497c 100644
> --- a/drivers/gpu/drm/bridge/sil-sii8620.c
> +++ b/drivers/gpu/drm/bridge/sil-sii8620.c
> @@ -978,6 +978,8 @@ static int sii8620_hw_off(struct sii8620 *ctx)
>  
>  static void sii8620_hw_reset(struct sii8620 *ctx)
>  {
> +	struct i2c_client *i2c = to_i2c_client(ctx->dev);
> +
>  	usleep_range(10000, 20000);
>  	gpiod_set_value(ctx->gpio_reset, 0);
>  	usleep_range(5000, 20000);
> @@ -985,6 +987,9 @@ static void sii8620_hw_reset(struct sii8620 *ctx)
>  	usleep_range(10000, 20000);
>  	gpiod_set_value(ctx->gpio_reset, 0);
>  	msleep(300);
> +
> +	/* I2C bus recovery prevents I2C errors due to known bug in the chip */
> +	i2c_recover_bus(i2c->adapter);
>  }
>  
>  static void sii8620_cbus_reset(struct sii8620 *ctx)

I have just posted patch which deals with the problem directly in i2c
adapter, so this patch can be dropped[1].

[1]: https://marc.info/?l=linux-i2c&m=151696860906805

Regards

Andrzej