linux-kernel - Re: [PATCH 0/4] Genericize DW MIPI DSI bridge and add i.MX 6 driver

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Message-ID: <CACvgo50NmofJrCvADOTxJqJqKEWDsy8qD-1B6R356vFMcmdbWA@mail.gmail.com>
Date:   Thu, 31 Oct 2019 17:07:36 +0000
From:   Emil Velikov <emil.l.velikov@...il.com>
To:     Adrian Ratiu <adrian.ratiu@...labora.com>
Cc:     LAKML <linux-arm-kernel@...ts.infradead.org>,
        linux-stm32@...md-mailman.stormreply.com,
        linux-rockchip <linux-rockchip@...ts.infradead.org>,
        kernel@...labora.com,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        ML dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH 0/4] Genericize DW MIPI DSI bridge and add i.MX 6 driver

Hi Adrian,

On Thu, 31 Oct 2019 at 14:26, Adrian Ratiu <adrian.ratiu@...labora.com> wrote:
>
> Having a generic Synopsis DesignWare MIPI-DSI host controller bridge
> driver is a very good idea, however the current implementation has
> hardcoded quite a lot of the register layouts used by the two supported
> SoC vendors, STM and Rockchip, which use IP cores v1.30 and v1.31.
>
> This makes it hard to support other SoC vendors like the FSL/NXP i.MX 6
> which use older v1.01 cores or future versions because, based on history,
> layout changes should also be expected in new DSI versions / SoCs.
>
> This patch series converts the bridge and platform drivers to access
> registers via generic regmap APIs and allows each platform driver to
> configure its register layout via struct reg_fields, then adds support
> for the host controller found on i.MX 6.
>
Have you considered keeping the difference internal to the dw-mipi-dsi driver?
Say having the iMX6 module "request" the v1.01 regmap from the bridge
driver, while rockchip/others doing the equivalent.

>  .../bindings/display/imx/mipi-dsi.txt         |  56 ++
>  drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 518 +++++++++---------
>  drivers/gpu/drm/imx/Kconfig                   |   7 +
>  drivers/gpu/drm/imx/Makefile                  |   1 +
>  drivers/gpu/drm/imx/dw_mipi_dsi-imx.c         | 502 +++++++++++++++++
>  .../gpu/drm/rockchip/dw-mipi-dsi-rockchip.c   | 154 +++++-
>  drivers/gpu/drm/stm/dw_mipi_dsi-stm.c         | 160 +++++-
>  include/drm/bridge/dw_mipi_dsi.h              |  60 +-
>  8 files changed, 1185 insertions(+), 273 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/display/imx/mipi-dsi.txt
>  create mode 100644 drivers/gpu/drm/imx/dw_mipi_dsi-imx.c
>

This should make the delta a lot smaller, avoiding the unnecessary
copy of register fields and regmap.
Plus plugging future users will be dead trivial.

-Emil