Re: [PATCH v12 00/18] drm: Add Samsung MIPI DSIM bridge

From: Alexander Stein <alexander.stein@ew.tq-group.com>
To: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Cc: Fabio Estevam <festevam@gmail.com>,
	dri-devel@lists.freedesktop.org, Marek Vasut <marex@denx.de>,
	linux-samsung-soc@vger.kernel.org, matteo.lisi@engicam.com,
	aford173@gmail.com, dri-devel@lists.freedesktop.org,
	sw0312.kim@samsung.com, linux-imx@nxp.com,
	Frieder Schrempf <frieder.schrempf@kontron.de>,
	kyungmin.park@samsung.com,
	Jagan Teki <jagan@amarulasolutions.com>,
	andrzej.hajda@intel.com, m.szyprowski@samsung.com,
	linux-amarula@amarulasolutions.com,
	linux-arm-kernel@lists.infradead.org,
	Laurent.pinchart@ideasonboard.com
Subject: Re: [PATCH v12 00/18] drm: Add Samsung MIPI DSIM bridge
Date: Fri, 17 Feb 2023 11:05:15 +0100	[thread overview]
Message-ID: <9068722.CDJkKcVGEf@steina-w> (raw)
In-Reply-To: <25ae1824-4f00-4337-4512-0d8190981fb6@prevas.dk>

Am Freitag, 17. Februar 2023, 09:55:22 CET schrieb Rasmus Villemoes:
> On 14/02/2023 12.09, Fabio Estevam wrote:
> > Hi Rasmus,
> > 
> > On Tue, Feb 14, 2023 at 7:55 AM Rasmus Villemoes
> > 
> > <rasmus.villemoes@prevas.dk> wrote:
> >> Well, the data sheet for the dsi86 says up to 750MHz DSI HS clock, and
> >> if the value specified in samsung,burst-clock-frequency is twice the DSI
> >> HS clk, I suppose I should be good up to 1.5GHz? I have tried many
> >> different values, but I never seem to get anything through; I think I'm
> >> missing some piece.
> >> 
> >> So now I've tried to use these patches on the imx8mp-evk with the
> >> mipi->hdmi accessory from NXP, just to see if I can ever get any
> >> graphics through the mipi interface. And there the story is the same:
> >> the adv7535 bridge gets probed, and can read out the edid from the
> >> monitor over hdmi. And while the mipi block and the bridge seem to
> >> attach to each other, I still don't get any output.
> >> 
> >> Do any of you happen to have this working on the imx8mp-evk, and if so,
> >> can you share the .dts updates you've done and how exactly you test the
> >> graphics?
> > 
> > I don't have access to an imx8mp-evk, but I tested the ADV7535 MIPI to
> > HDMI daughter card on an imx8mm-evk.
> > 
> > Some extra ADV7535 patches were needed. Please check patches 0020-0023
> > and see if they help.
> 
> Thanks, but they don't seem to make a difference.
> 
> I've started trying to simply compare registers between the NXP 5.15
> kernel and the imx8mm-dsi-v12 branch with Marek's patch on top. Already
> in MEDIA_BLK_CTRL, 0x32ec0000, there's something interesting:
> 
>  ## Media Mix Clock Enable Register
> -CLK_EN                 0004    0080e133
> +CLK_EN                 0004    00800133
>  ## MIPI PHY Control Register
> -MIPI_RESET_DIV         0008    40030000
> +MIPI_RESET_DIV         0008    00020000
> 
> So with the NXP kernel, there are three bits set in CLK_EN which are not
> set with the "mainline", but those bits are marked reserved in the RM,
> so I have no idea if they are just some RO bits that get set due to some
> other munging. Then there's the MIPI_RESET_DIV register where bits 16
> and 30 do not get set. Of course, there are lots of other differences,
> but perhaps this gives somebody an idea.

Looking at drivers/soc/imx/imx8m-blk-ctrl.c the bits for MIPI_RESET_DIV are
16: MIPI_CSI1
17: MIPI_DSI
30: MIPI_CSI2
So i think that's okay here.

Best regards,
Alexander
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