Received-SPF: pass (google.com: domain of linux-kernel+bounces-152515-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Message-ID: <9c4a3bdd-fd57-4664-a908-ab1c8020e918@denx.de>
Date: Sun, 21 Apr 2024 16:05:08 +0200
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH V2 1/2] drm/bridge: samsung-dsim: Set P divider based on
 min/max of fin pll
To: Adam Ford <aford173@gmail.com>, dri-devel@lists.freedesktop.org
Cc: aford@beaconembedded.com, Frieder Schrempf <frieder.schrempf@kontron.de>,
 Inki Dae <inki.dae@samsung.com>, Jagan Teki <jagan@amarulasolutions.com>,
 Marek Szyprowski <m.szyprowski@samsung.com>,
 Andrzej Hajda <andrzej.hajda@intel.com>,
 Neil Armstrong <neil.armstrong@linaro.org>, Robert Foss <rfoss@kernel.org>,
 Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
 Jonas Karlman <jonas@kwiboo.se>, Jernej Skrabec <jernej.skrabec@gmail.com>,
 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
 Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>,
 David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
 Marco Felsch <m.felsch@pengutronix.de>,
 Michael Tretter <m.tretter@pengutronix.de>, linux-kernel@vger.kernel.org
References: <20240211230931.188194-1-aford173@gmail.com>
Content-Language: en-US
From: Marek Vasut <marex@denx.de>
In-Reply-To: <20240211230931.188194-1-aford173@gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

On 2/12/24 12:09 AM, Adam Ford wrote:
> The P divider should be set based on the min and max values of
> the fin pll which may vary between different platforms.
> These ranges are defined per platform, but hard-coded values
> were used instead which resulted in a smaller range available
> on the i.MX8M[MNP] than what was possible.
> 
> As noted by Frieder, there are descripencies between the reference
> manuals of the Mini, Nano and Plus, so I reached out to my NXP
> rep and got the following response regarding the varing notes
> in the documentation.
> 
> "Yes it is definitely wrong, the one that is part of the NOTE in
> MIPI_DPHY_M_PLLPMS register table against PMS_P, PMS_M and PMS_S is
> not correct. I will report this to Doc team, the one customer should
> be take into account is the Table 13-40 DPHY PLL Parameters and the
> Note above."
> 
> With this patch, the clock rates now match the values used in NXP's
> downstream kernel.
> 
> Fixes: 846307185f0f ("drm/bridge: samsung-dsim: update PLL reference clock")
> Signed-off-by: Adam Ford <aford173@gmail.com>
> Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> ---
> V2:  Only update the commit message to reflect why these values
>       were chosen.  No code change present
> 
> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> index 95fedc68b0ae..8476650c477c 100644
> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> @@ -574,8 +574,8 @@ static unsigned long samsung_dsim_pll_find_pms(struct samsung_dsim *dsi,
>   	u16 _m, best_m;
>   	u8 _s, best_s;
>   
> -	p_min = DIV_ROUND_UP(fin, (12 * MHZ));
> -	p_max = fin / (6 * MHZ);
> +	p_min = DIV_ROUND_UP(fin, (driver_data->pll_fin_max * MHZ));

The parenthesis around driver_data... are not needed.

With that fixed:

Reviewed-by: Marek Vasut <marex@denx.de>