linux-kernel - Re: [PATCH 4/4] drm/panel: samsung-s6e88a0-ams427ap24: Add flip option

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Message-ID: <1e23cfa8-66c6-476b-927c-695172e76143@quicinc.com>
Date: Fri, 11 Oct 2024 10:17:55 -0700
From: Jessica Zhang <quic_jesszhan@...cinc.com>
To: Jakob Hauser <jahau@...ketmail.com>,
        Neil Armstrong
	<neil.armstrong@...aro.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof
 Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>
CC: <dri-devel@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <~postmarketos/upstreaming@...ts.sr.ht>
Subject: Re: [PATCH 4/4] drm/panel: samsung-s6e88a0-ams427ap24: Add flip
 option



On 10/10/2024 11:31 AM, Jakob Hauser wrote:
> The way of implementing a flip option follows the existing
> panel-samsung-s6e8aa0.c [1][2][3].
> 
> The value to flip the screen is taken from a downstream kernel file of
> a similar but older panel [4]. The mipi clock [5] for the new panel
> samsung-s6e88a0-ams427ap24 matches 461 MHz and a hardware read-out of the
> 0xcb values corresponds to revision R01 of that older panel [6]. Although
> for samsung-s6e88a0-ams427ap24 that's in non-flipped state while in this
> older driver it seems to be the other way around. Further up there is a

Hi Jakob,

I'm a bit confused by the wording here. Do you mean that even though the 
downstream driver comments state the panel is in a non-flipped state by 
default, your observations suggest that it's actually defaulting to a 
flipped state?

Thanks,

Jessica Zhang

> hint [7] basically saying for revision R01 to change the first word of the
> 0xcb command from 0x06 to 0x0e, which is actually setting BIT(3) of that
> word. This causes a horizontal flip.
> 
> [1] https://github.com/torvalds/linux/blob/v6.11/drivers/gpu/drm/panel/panel-samsung-s6e8aa0.c#L103
> [2] https://github.com/torvalds/linux/blob/v6.11/drivers/gpu/drm/panel/panel-samsung-s6e8aa0.c#L207-L211
> [3] https://github.com/torvalds/linux/blob/v6.11/drivers/gpu/drm/panel/panel-samsung-s6e8aa0.c#L954-L974
> [4] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-15.1/drivers/video/msm/mipi_samsung_oled_video_qhd_pt-8930.c
> [5] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-15.1/drivers/video/msm/mipi_samsung_oled_video_qhd_pt-8930.c#L2027-L2028
> [6] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-15.1/drivers/video/msm/mipi_samsung_oled_video_qhd_pt-8930.c#L137-L151
> [7] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-15.1/drivers/video/msm/mipi_samsung_oled_video_qhd_pt-8930.c#L66-L74
> 
> Signed-off-by: Jakob Hauser <jahau@...ketmail.com>
> ---
>   .../drm/panel/panel-samsung-s6e88a0-ams427ap24.c | 16 ++++++++++++++++
>   1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panel/panel-samsung-s6e88a0-ams427ap24.c b/drivers/gpu/drm/panel/panel-samsung-s6e88a0-ams427ap24.c
> index 657120d7dd33..4d5c494e03ae 100644
> --- a/drivers/gpu/drm/panel/panel-samsung-s6e88a0-ams427ap24.c
> +++ b/drivers/gpu/drm/panel/panel-samsung-s6e88a0-ams427ap24.c
> @@ -32,6 +32,7 @@ struct s6e88a0_ams427ap24 {
>   	struct mipi_dsi_device *dsi;
>   	struct regulator_bulk_data *supplies;
>   	struct gpio_desc *reset_gpio;
> +	bool flip_horizontal;
>   	bool prepared;
>   };
>   
> @@ -539,6 +540,10 @@ static int s6e88a0_ams427ap24_on(struct s6e88a0_ams427ap24 *ctx)
>   	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xcc, 0x4c);
>   	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf2, 0x03, 0x0d);
>   	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf1, 0xa5, 0xa5);
> +
> +	if (ctx->flip_horizontal)
> +		mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xcb, 0x0e);
> +
>   	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf0, 0xa5, 0xa5);
>   	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xfc, 0xa5, 0xa5);
>   
> @@ -673,6 +678,15 @@ static int s6e88a0_ams427ap24_register_backlight(struct s6e88a0_ams427ap24 *ctx)
>   	return ret;
>   }
>   
> +static void s6e88a0_ams427ap24_parse_dt(struct s6e88a0_ams427ap24 *ctx)
> +{
> +	struct mipi_dsi_device *dsi = ctx->dsi;
> +	struct device *dev = &dsi->dev;
> +	struct device_node *np = dev->of_node;
> +
> +	ctx->flip_horizontal = of_property_read_bool(np, "flip-horizontal");
> +}
> +
>   static int s6e88a0_ams427ap24_probe(struct mipi_dsi_device *dsi)
>   {
>   	struct device *dev = &dsi->dev;
> @@ -707,6 +721,8 @@ static int s6e88a0_ams427ap24_probe(struct mipi_dsi_device *dsi)
>   		       DRM_MODE_CONNECTOR_DSI);
>   	ctx->panel.prepare_prev_first = true;
>   
> +	s6e88a0_ams427ap24_parse_dt(ctx);
> +
>   	ret = s6e88a0_ams427ap24_register_backlight(ctx);
>   	if (ret < 0)
>   		return ret;
> -- 
> 2.39.5
>