linux-kernel - Re: [PATCH v4 04/11] drm/bridge: it6505: fix aux command write to aux operaction register

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Message-ID: <fcy6i4cfmtpsgnvuqfjm7pwlkyuno65rij5w32snmjbudma6wp@ht2jqtj2rsxq>
Date: Thu, 26 Sep 2024 11:01:17 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Hermes Wu <Hermes.Wu@....com.tw>
Cc: Kenneth Hung <Kenneth.hung@....com.tw>, 
	Andrzej Hajda <andrzej.hajda@...el.com>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Robert Foss <rfoss@...nel.org>, Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
	Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Allen Chen <allen.chen@....com.tw>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>, 
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 04/11] drm/bridge: it6505: fix aux command write to
 aux operaction register

On Thu, Sep 26, 2024 at 03:47:54PM GMT, Hermes Wu wrote:
> From: Hermes Wu <Hermes.wu@....com.tw>
> 
> The aux control register command is 4 bits LSB only, adding a MACRO to get
> correct operaction command.

Nit: AUX, add (not adding), macro.

What happens if the driver doesn't limit the field? Let me guess, the
KSV reading command is 0x10 (it should have been a part of the commit
message, BTW), so it overrides some other bits? In such a case this
either should be a part of the previous commit, or, at least, come
before it.

> Fixes: b5c84a9edcd4 ("drm/bridge: add it6505 driver")
> Signed-off-by: Hermes Wu <Hermes.wu@....com.tw>
> ---
>  drivers/gpu/drm/bridge/ite-it6505.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
> index 0583abdca75f..d1f5220e04a6 100644
> --- a/drivers/gpu/drm/bridge/ite-it6505.c
> +++ b/drivers/gpu/drm/bridge/ite-it6505.c
> @@ -329,6 +329,8 @@ enum aux_cmd_type {
>  	CMD_AUX_GET_KSV_LIST = 0x10,
>  };
>  
> +#define GET_AUX_CONTROL_CODE(cmd) ((cmd) & 0x0F)
> +
>  enum aux_cmd_reply {
>  	REPLY_ACK,
>  	REPLY_NACK,
> @@ -1000,7 +1002,7 @@ static ssize_t it6505_aux_operation(struct it6505 *it6505,
>  				  size);
>  
>  	/* Aux Fire */
> -	it6505_write(it6505, REG_AUX_CMD_REQ, cmd);
> +	it6505_write(it6505, REG_AUX_CMD_REQ, GET_AUX_CONTROL_CODE(cmd));
>  
>  	ret = it6505_aux_wait(it6505);
>  	if (ret < 0)
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry