linux-kernel - Re: [PATCH v3 06/15] drm/bridge: tc358767: Simplify AUX data read

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Date:   Thu, 6 Jun 2019 12:59:20 +0200
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>,
        dri-devel@...ts.freedesktop.org
Cc:     Archit Taneja <architt@...eaurora.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Andrey Gusakov <andrey.gusakov@...entembedded.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Cory Tusar <cory.tusar@....aero>,
        Chris Healy <cphealy@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 06/15] drm/bridge: tc358767: Simplify AUX data read

On 05.06.2019 09:04, Andrey Smirnov wrote:
> Simplify AUX data read by removing index arithmetic and shifting with
> a helper functions that does three things:
>
>     1. Fetch data from up to 4 32-bit registers from the chip
>     2. Optionally fix data endianness (not needed on LE hosts)
>     3. Copy read data into user provided array.
>
> Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
> Cc: Archit Taneja <architt@...eaurora.org>
> Cc: Andrzej Hajda <a.hajda@...sung.com>
> Cc: Laurent Pinchart <Laurent.pinchart@...asonboard.com>
> Cc: Tomi Valkeinen <tomi.valkeinen@...com>
> Cc: Andrey Gusakov <andrey.gusakov@...entembedded.com>
> Cc: Philipp Zabel <p.zabel@...gutronix.de>
> Cc: Cory Tusar <cory.tusar@....aero>
> Cc: Chris Healy <cphealy@...il.com>
> Cc: Lucas Stach <l.stach@...gutronix.de>
> Cc: dri-devel@...ts.freedesktop.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  drivers/gpu/drm/bridge/tc358767.c | 40 +++++++++++++++++++++----------
>  1 file changed, 27 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
> index e197ce0fb166..da47d81e7109 100644
> --- a/drivers/gpu/drm/bridge/tc358767.c
> +++ b/drivers/gpu/drm/bridge/tc358767.c
> @@ -321,6 +321,29 @@ static int tc_aux_get_status(struct tc_data *tc, u8 *reply)
>  	return 0;
>  }
>  
> +static int tc_aux_read_data(struct tc_data *tc, void *data, size_t size)
> +{
> +	u32 auxrdata[DP_AUX_MAX_PAYLOAD_BYTES / sizeof(u32)];
> +	int ret, i, count = DIV_ROUND_UP(size, sizeof(u32));
> +
> +	ret = regmap_bulk_read(tc->regmap, DP0_AUXRDATA(0), auxrdata, count);
> +	if (ret)
> +		return ret;
> +
> +	for (i = 0; i < count; i++) {
> +		/*
> +		 * Our regmap is configured as LE for register data,
> +		 * so we need undo any byte swapping that might have
> +		 * happened to preserve original byte order.
> +		 */
> +		le32_to_cpus(&auxrdata[i]);
> +	}
> +
> +	memcpy(data, auxrdata, size);
> +
> +	return size;
> +}
> +


Hmm, cannot we just use regmap_raw_read?

Beside this:

Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>

 --
Regards
Andrzej



>  static ssize_t tc_aux_transfer(struct drm_dp_aux *aux,
>  			       struct drm_dp_aux_msg *msg)
>  {
> @@ -379,19 +402,10 @@ static ssize_t tc_aux_transfer(struct drm_dp_aux *aux,
>  	if (ret)
>  		return ret;
>  
> -	if (request == DP_AUX_I2C_READ || request == DP_AUX_NATIVE_READ) {
> -		/* Read data */
> -		while (i < size) {
> -			if ((i % 4) == 0) {
> -				ret = regmap_read(tc->regmap,
> -						  DP0_AUXRDATA(i >> 2), &tmp);
> -				if (ret)
> -					return ret;
> -			}
> -			buf[i] = tmp & 0xff;
> -			tmp = tmp >> 8;
> -			i++;
> -		}
> +	switch (request) {
> +	case DP_AUX_NATIVE_READ:
> +	case DP_AUX_I2C_READ:
> +		return tc_aux_read_data(tc, msg->buffer, size);
>  	}
>  
>  	return size;