Re: [PATCH v3] drm/rcar-du: dsi: Implement DSI command TX using AXI memory access

[Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>]

Hi,

On 10/09/2026 21:19, Marek Vasut wrote:
> Currently, the driver supports register access mode for DSI command
> transfer, which limits both TX and RX to only 16 Bytes long packets.
> Implement support for DSI command TX using AXI memory access mode,
> which extends the packet transfer length up to 128 Bytes long in LP
> and 1024 Bytes long in HS. Support for DSI command RX using the AXI
> access mode is not implemented due to missing test hardware.
> 
> The implementation allocates a DMAble 4k page. In case the command
> transfer is longer than 16 Bytes, the payload is copied into the
> page and sent out using the AXI access mode, otherwise the register
> access mode is used.
> 
> Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
> ---
> Cc: David Airlie <airlied@gmail.com>
> Cc: Geert Uytterhoeven <geert+renesas@glider.be>
> Cc: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
> Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Magnus Damm <magnus.damm@gmail.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Simona Vetter <simona@ffwll.ch>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
> Cc: dri-devel@lists.freedesktop.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-renesas-soc@vger.kernel.org
> ---
> V2: - Use dma_set_mask_and_coherent() to set up global DMA mask and
>        drop GFP_DMA32 from dma_alloc_coherent() gfp flags.
>      - Fix DMA memory leak in missing fail path in rcar_mipi_dsi_probe()
>        and move dma_alloc_coherent() almost to the end of the probe
>        function, so as much as possible of the probe function is devm
>        managed.
>      - Unregister DSI host first, then free the DMA page
> V3: - Limit transfer to 1024 Bytes
> ---
>   .../gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c   | 50 ++++++++++++++++---
>   1 file changed, 42 insertions(+), 8 deletions(-)
Reviewed-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>

  Tomi