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Message-ID: <20250623120149.GA19319@pendragon.ideasonboard.com>
Date: Mon, 23 Jun 2025 15:01:49 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Dharma Balasubiramani <dharma.b@...rochip.com>
Cc: Manikandan Muralidharan <manikandan.m@...rochip.com>,
Andrzej Hajda <andrzej.hajda@...el.com>,
Neil Armstrong <neil.armstrong@...aro.org>,
Robert Foss <rfoss@...nel.org>, 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>,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
Sandeep Sheriker M <sandeep.sheriker@...rochip.com>
Subject: Re: [PATCH v2] drm/bridge: microchip-lvds: fix bus format mismatch
with VESA displays
Hi Dharma,
Thank you for the patch.
On Mon, Jun 23, 2025 at 04:20:20PM +0530, Dharma Balasubiramani wrote:
> From: Sandeep Sheriker M <sandeep.sheriker@...rochip.com>
>
> The LVDS controller was hardcoded to JEIDA mapping, which leads to
> distorted output on panels expecting VESA mapping.
>
> Update the driver to dynamically select the appropriate mapping and
> pixel size based on the panel's advertised media bus format. This
> ensures compatibility with both JEIDA and VESA displays.
>
> Modernize the bridge ops to use atomic_enable/disable, and retrieve
> the bus format from the connector via the atomic bridge state.
>
> Signed-off-by: Sandeep Sheriker M <sandeep.sheriker@...rochip.com>
> Signed-off-by: Dharma Balasubiramani <dharma.b@...rochip.com>
> ---
> Note: Tested the changes on newvision 10.1 VESA display.
>
> Changes in v2:
> - Switch to atomic bridge functions
> - Drop custom connector creation
> - Use drm_atomic_get_new_connector_for_encoder()
> - Link to v1: https://lore.kernel.org/r/20250618-microchip-lvds-v1-1-1eae5acd7a82@microchip.com
> ---
> drivers/gpu/drm/bridge/microchip-lvds.c | 64 +++++++++++++++++++++++++++------
> 1 file changed, 54 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/microchip-lvds.c b/drivers/gpu/drm/bridge/microchip-lvds.c
> index 9f4ff82bc6b4..b71478aa36e9 100644
> --- a/drivers/gpu/drm/bridge/microchip-lvds.c
> +++ b/drivers/gpu/drm/bridge/microchip-lvds.c
> @@ -11,6 +11,7 @@
> #include <linux/component.h>
> #include <linux/delay.h>
> #include <linux/jiffies.h>
> +#include <linux/media-bus-format.h>
> #include <linux/mfd/syscon.h>
> #include <linux/of_graph.h>
> #include <linux/pinctrl/devinfo.h>
> @@ -41,9 +42,11 @@
>
> /* Bitfields in LVDSC_CFGR (Configuration Register) */
> #define LVDSC_CFGR_PIXSIZE_24BITS 0
> +#define LVDSC_CFGR_PIXSIZE_18BITS 1
#define LVDSC_CFGR_PIXSIZE_18BITS BIT(0)
> #define LVDSC_CFGR_DEN_POL_HIGH 0
> #define LVDSC_CFGR_DC_UNBALANCED 0
> #define LVDSC_CFGR_MAPPING_JEIDA BIT(6)
> +#define LVDSC_CFGR_MAPPING_VESA 0
>
> /*Bitfields in LVDSC_SR */
> #define LVDSC_SR_CS BIT(0)
I think you can drop the panel field of the mchp_lvds structure in the
same patch.
> @@ -76,9 +79,10 @@ static inline void lvds_writel(struct mchp_lvds *lvds, u32 offset, u32 val)
> writel_relaxed(val, lvds->regs + offset);
> }
>
> -static void lvds_serialiser_on(struct mchp_lvds *lvds)
> +static void lvds_serialiser_on(struct mchp_lvds *lvds, u32 bus_format)
> {
> unsigned long timeout = jiffies + msecs_to_jiffies(LVDS_POLL_TIMEOUT_MS);
> + u8 map, pix_size;
>
> /* The LVDSC registers can only be written if WPEN is cleared */
> lvds_writel(lvds, LVDSC_WPMR, (LVDSC_WPMR_WPKEY_PSSWD &
> @@ -93,11 +97,24 @@ static void lvds_serialiser_on(struct mchp_lvds *lvds)
> usleep_range(1000, 2000);
> }
>
> + switch (bus_format) {
> + case MEDIA_BUS_FMT_RGB666_1X7X3_SPWG:
> + map = LVDSC_CFGR_MAPPING_JEIDA;
> + pix_size = LVDSC_CFGR_PIXSIZE_18BITS;
> + break;
> + case MEDIA_BUS_FMT_RGB888_1X7X4_SPWG:
> + map = LVDSC_CFGR_MAPPING_VESA;
> + pix_size = LVDSC_CFGR_PIXSIZE_24BITS;
> + break;
> + default:
> + map = LVDSC_CFGR_MAPPING_JEIDA;
> + pix_size = LVDSC_CFGR_PIXSIZE_24BITS;
> + break;
> + }
> +
> /* Configure the LVDSC */
> - lvds_writel(lvds, LVDSC_CFGR, (LVDSC_CFGR_MAPPING_JEIDA |
> - LVDSC_CFGR_DC_UNBALANCED |
> - LVDSC_CFGR_DEN_POL_HIGH |
> - LVDSC_CFGR_PIXSIZE_24BITS));
> + lvds_writel(lvds, LVDSC_CFGR, (map | LVDSC_CFGR_DC_UNBALANCED |
> + LVDSC_CFGR_DEN_POL_HIGH | pix_size));
You can drop the inner parentheses.
>
> /* Enable the LVDS serializer */
> lvds_writel(lvds, LVDSC_CR, LVDSC_CR_SER_EN);
> @@ -113,7 +130,8 @@ static int mchp_lvds_attach(struct drm_bridge *bridge,
> bridge, flags);
> }
>
> -static void mchp_lvds_enable(struct drm_bridge *bridge)
> +static void mchp_lvds_atomic_pre_enable(struct drm_bridge *bridge,
> + struct drm_atomic_state *state)
> {
> struct mchp_lvds *lvds = bridge_to_lvds(bridge);
> int ret;
> @@ -129,11 +147,35 @@ static void mchp_lvds_enable(struct drm_bridge *bridge)
> dev_err(lvds->dev, "failed to get pm runtime: %d\n", ret);
> return;
> }
> +}
> +
> +static void mchp_lvds_atomic_enable(struct drm_bridge *bridge,
> + struct drm_atomic_state *state)
> +{
> + struct mchp_lvds *lvds = bridge_to_lvds(bridge);
> + struct drm_connector *connector;
> +
> + /* default to jeida-24 */
> + u32 bus_format = MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA;
> +
> + connector = drm_atomic_get_new_connector_for_encoder(state, bridge->encoder);
> + if (connector && connector->display_info.num_bus_formats)
> + bus_format = connector->display_info.bus_formats[0];
> +
> + lvds_serialiser_on(lvds, bus_format);
> +}
> +
> +static void mchp_lvds_atomic_disable(struct drm_bridge *bridge,
> + struct drm_atomic_state *state)
> +{
> + struct mchp_lvds *lvds = bridge_to_lvds(bridge);
>
> - lvds_serialiser_on(lvds);
> + /* Turn off the serialiser */
> + lvds_writel(lvds, LVDSC_CR, 0);
> }
>
> -static void mchp_lvds_disable(struct drm_bridge *bridge)
> +static void mchp_lvds_atomic_post_disable(struct drm_bridge *bridge,
> + struct drm_atomic_state *state)
> {
> struct mchp_lvds *lvds = bridge_to_lvds(bridge);
>
> @@ -143,8 +185,10 @@ static void mchp_lvds_disable(struct drm_bridge *bridge)
>
> static const struct drm_bridge_funcs mchp_lvds_bridge_funcs = {
> .attach = mchp_lvds_attach,
> - .enable = mchp_lvds_enable,
> - .disable = mchp_lvds_disable,
> + .atomic_pre_enable = mchp_lvds_atomic_pre_enable,
> + .atomic_enable = mchp_lvds_atomic_enable,
> + .atomic_disable = mchp_lvds_atomic_disable,
> + .atomic_post_disable = mchp_lvds_atomic_post_disable,
> };
>
> static int mchp_lvds_probe(struct platform_device *pdev)
>
> ---
> base-commit: 4325743c7e209ae7845293679a4de94b969f2bef
> change-id: 20250618-microchip-lvds-b7151d96094a
--
Regards,
Laurent Pinchart
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