linux-kernel - Re: [RFC PATCH 4/6] drm: mxc-epdc: Add update management

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Message-ID: <Yi0A5inJh0Whkh5n@latitude>
Date:   Sat, 12 Mar 2022 21:21:58 +0100
From:   Jonathan Neuschäfer <j.neuschaefer@....net>
To:     Andreas Kemnade <andreas@...nade.info>
Cc:     p.zabel@...gutronix.de, airlied@...ux.ie, daniel@...ll.ch,
        robh+dt@...nel.org, shawnguo@...nel.org, s.hauer@...gutronix.de,
        kernel@...gutronix.de, festevam@...il.com, linux-imx@....com,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, dri-devel@...ts.freedesktop.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, alistair@...stair23.me,
        samuel@...lland.org, josua.mayer@....eu,
        letux-kernel@...nphoenux.org
Subject: Re: [RFC PATCH 4/6] drm: mxc-epdc: Add update management

On Sun, Feb 06, 2022 at 09:00:14AM +0100, Andreas Kemnade wrote:
> The EPDC can process some dirty rectangles at a time, pick them up and
> forward them to the controller. Only processes not involving PXP are
> supported at the moment. Due to that and to work with more waveforms,
> there is some masking/shifting done. It was tested with the factory
> waveforms of Kobo Clara HD, Tolino Shine 3, and Tolino Shine 2HD.
> Also the waveform called epdc_E060SCM.fw from NXP BSP works with the
> i.MX6SL devices.
> 
> Signed-off-by: Andreas Kemnade <andreas@...nade.info>
> ---

[...]
> +	adj_update_region = upd_data_list->update_desc->upd_data.update_region;
> +	/*
> +	 * Is the working buffer idle?
> +	 * If the working buffer is busy, we must wait for the resource
> +	 * to become free. The IST will signal this event.

What does IST mean?


> +void mxc_epdc_draw_mode0(struct mxc_epdc *priv)

What does mode 0 imply? An overview of the possible modes would be
appreciated.

> +{
> +	u32 *upd_buf_ptr;
> +	int i;
> +	u32 xres, yres;
> +
> +	upd_buf_ptr = (u32 *)priv->epdc_mem_virt;
> +
> +	epdc_working_buf_intr(priv, true);
> +	epdc_lut_complete_intr(priv, 0, true);
> +
> +	/* Use unrotated (native) width/height */
> +	xres = priv->epdc_mem_width;
> +	yres = priv->epdc_mem_height;
> +
> +	/* Program EPDC update to process buffer */
> +	epdc_set_update_area(priv, priv->epdc_mem_phys, 0, 0, xres, yres, 0);
> +	epdc_submit_update(priv, 0, priv->wv_modes.mode_init, UPDATE_MODE_FULL,
> +		false, true, 0xFF);
> +
> +	dev_dbg(priv->drm.dev, "Mode0 update - Waiting for LUT to complete...\n");
> +
> +	/* Will timeout after ~4-5 seconds */
> +
> +	for (i = 0; i < 40; i++) {
> +		if (!epdc_is_lut_active(priv, 0)) {
> +			dev_dbg(priv->drm.dev, "Mode0 init complete\n");
> +			return;
> +		}
> +		msleep(100);
> +	}
> +
> +	dev_err(priv->drm.dev, "Mode0 init failed!\n");
> +}

> +#define WAVEFORM_MODE_GLR16			4
> +#define WAVEFORM_MODE_GLD16			5
> +#define WAVEFORM_MODE_AUTO			257

(How) are these mode numbers related to "mode 0"?


Jonathan

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