From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BEE23CD6E41 for ; Wed, 27 May 2026 14:04:22 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 02C9C10E819; Wed, 27 May 2026 14:04:22 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=collabora.com header.i=nicolas.frattaroli@collabora.com header.b="F0TOpfs/"; dkim-atps=neutral Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7B2C810E577 for ; Wed, 27 May 2026 14:04:19 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; t=1779890651; cv=none; d=zohomail.com; s=zohoarc; b=FpnMQEhLNnuKwfoDAX9zUZ/P0hzDFmadDjhpCI+MyddxwCeiiSfvG48n8YuVuUBqILFaqZi3Ia++JdbYWH2CFAxPomKc7z08cdNCkhqmFX5yDPoSfW5v4USops/dB5slOzRH4CB324+9XkymoXClVxlFvnIizFlq85KrkRbAFVE= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1779890651; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=AePNlg/tPONqMp07nxRxcyXDUmpSdhz9BPkGf90Crqs=; b=PVaGHNDOLa30CAPjdaV19T7VzoquHX1oa6nAq385aNSpMMS9o7HrToQ8IPdnAkScZd5bjz0/6Gp+s0vKAxa6KWOqyRMieeZxua2BopHg2t2fhd5gIXEzHhTG5AmI5o2oFILZrQ2LoRK3KG3OG7U+TevOJnHHhES+fYEIRP9gjsg= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=nicolas.frattaroli@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1779890651; s=zohomail; d=collabora.com; i=nicolas.frattaroli@collabora.com; h=From:From:Date:Date:Subject:Subject:MIME-Version:Content-Type:Content-Transfer-Encoding:Message-Id:Message-Id:References:In-Reply-To:To:To:Cc:Cc:Reply-To; bh=AePNlg/tPONqMp07nxRxcyXDUmpSdhz9BPkGf90Crqs=; b=F0TOpfs/GgObbMlbXejubESD84tHDGYkalcfjte1kut13LlZ4bGIu6Z3XEIAwPRD LXT9TfpG3J/1Vg57WFtaPk5xsH5S5af65BhaMXHtDYoAKSyUX2OQOWEx23O9rf6ApcU sEzOj+7pp9/SayyYtMiA5P6X06JOBONFJrSQWZhk= Received: by mx.zohomail.com with SMTPS id 1779890650636147.08368009246385; Wed, 27 May 2026 07:04:10 -0700 (PDT) From: Nicolas Frattaroli Date: Wed, 27 May 2026 16:03:43 +0200 Subject: [PATCH v4 2/4] drm/scdc-helper: Add scdc_status debugfs entry MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260527-scdc-link-health-v4-2-622ea40a1f59@collabora.com> References: <20260527-scdc-link-health-v4-0-622ea40a1f59@collabora.com> In-Reply-To: <20260527-scdc-link-health-v4-0-622ea40a1f59@collabora.com> To: Jani Nikula , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Daniel Stone Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com, Nicolas Frattaroli X-Mailer: b4 0.15.2 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" SCDC provides status information on the current display link. At the very least, it may be useful to expose this info through debugfs. Add a debugfs entry for it under the connector, which displays a few more details parsed out of the SCDC registers. A new drm_scdc_debugfs_init function can be called by the connector implementation to initialise the debugfs file. Signed-off-by: Nicolas Frattaroli --- drivers/gpu/drm/display/drm_scdc_helper.c | 237 ++++++++++++++++++++++++++++++ include/drm/display/drm_scdc_helper.h | 32 ++++ 2 files changed, 269 insertions(+) diff --git a/drivers/gpu/drm/display/drm_scdc_helper.c b/drivers/gpu/drm/display/drm_scdc_helper.c index 8403f2390ab6..7739fb5e77a1 100644 --- a/drivers/gpu/drm/display/drm_scdc_helper.c +++ b/drivers/gpu/drm/display/drm_scdc_helper.c @@ -24,11 +24,14 @@ #include #include #include +#include #include +#include #include #include #include +#include #include /** @@ -55,6 +58,11 @@ #define SCDC_I2C_SLAVE_ADDRESS 0x54 +struct scdc_debugfs_priv { + struct drm_connector *connector; + struct drm_scdc_state state; +}; + /** * drm_scdc_read - read a block of data from SCDC * @adapter: I2C controller @@ -276,3 +284,232 @@ bool drm_scdc_set_high_tmds_clock_ratio(struct drm_connector *connector, return true; } EXPORT_SYMBOL(drm_scdc_set_high_tmds_clock_ratio); + +/** + * drm_scdc_read_status0_flags - Read SCDC "Status Flags" Register + * @connector: pointer to &struct drm_connector to issue the scdc request on + * @flags: pointer to the caller's &struct drm_scdc_status_flags to output to + * + * Reads the SCDC Status Flags 0 register, and outputs its contents to the + * destination @flags. Contents of @flags are only valid if function returns 0. + * + * Returns: %0 on success, negative errno on error. + */ +int drm_scdc_read_status0_flags(struct drm_connector *connector, + struct drm_scdc_status_flags *flags) +{ + int ret; + u8 val; + + ret = drm_scdc_writeb(connector->ddc, SCDC_UPDATE_0, SCDC_STATUS_UPDATE); + if (ret) + return ret; + + ret = drm_scdc_readb(connector->ddc, SCDC_STATUS_FLAGS_0, &val); + if (ret) + return ret; + + flags->clock_detected = val & SCDC_CLOCK_DETECT; + flags->ch0_locked = val & SCDC_CH0_LOCK; + flags->ch1_locked = val & SCDC_CH1_LOCK; + flags->ch2_locked = val & SCDC_CH2_LOCK; + + return 0; +} +EXPORT_SYMBOL(drm_scdc_read_status0_flags); + +/** + * drm_scdc_read_error_counters - Read and clear SCDC error counters + * @connector: pointer to &struct drm_connector to issue the scdc request on + * @counter: Caller's u16 array with 3 elements to write the counter values into + * + * Read the SCDC channel error counters. If the count of channel *n* is valid, + * write it into counter[n]. Otherwise, set counter[n] to 0. Reads all counters + * in one read chunk, then clears every counter, as is mandated. + * + * Returns: %0 on success, negative errno on error. + */ +int drm_scdc_read_error_counters(struct drm_connector *connector, u16 counter[3]) +{ + u8 buf[7] = {}; + int ret; + u8 sum = 0; + int i; + + ret = drm_scdc_writeb(connector->ddc, SCDC_UPDATE_0, SCDC_CED_UPDATE); + if (ret) + return ret; + + ret = drm_scdc_read(connector->ddc, SCDC_ERR_DET_0_L, buf, ARRAY_SIZE(buf)); + if (ret) + return ret; + + /* + * Verify the "checksum", i.e. sum up everything including the checksum + * register as a wrapping unsigned 8-bit addition and verify it's 0. + */ + for (i = 0; i < ARRAY_SIZE(buf); i++) + sum = wrapping_add(u8, sum, buf[i]); + + if (sum) + return -EPROTO; + + for (i = 0; i < ARRAY_SIZE(buf) - 1; i += 2) { + if (buf[i + 1] & SCDC_CHANNEL_VALID) + counter[i / 2] = buf[i] | (buf[i + 1] & ~SCDC_CHANNEL_VALID) << 8; + else + counter[i / 2] = 0; + + buf[i] = 0; + buf[i + 1] = 0; + } + buf[ARRAY_SIZE(buf) - 1] = 0; + + return drm_scdc_write(connector->ddc, SCDC_ERR_DET_0_L, buf, ARRAY_SIZE(buf)); +} +EXPORT_SYMBOL(drm_scdc_read_error_counters); + +/** + * drm_scdc_read_state - Update state from SCDC + * @connector: pointer to a &struct drm_connector on which to operate on + * @state: pointer to a &struct drm_scdc_state to fill + * + * Reads update flags from SCDC, and updates the parts of @state that SCDC + * claims have changed, as well as populating those where such a distinction + * can't be made. + * + * Returns: %0 on success, negative errno on failure. + */ +int drm_scdc_read_state(struct drm_connector *connector, struct drm_scdc_state *state) +{ + u8 upd_flags[2] = {}; + struct i2c_adapter *ddc; + struct drm_scdc *scdc; + int ret; + u8 val; + + if (!state || !connector) + return -ENODEV; + + scdc = &connector->display_info.hdmi.scdc; + ddc = connector->ddc; + + if (!scdc->supported) + return -EOPNOTSUPP; + + ret = drm_scdc_readb(ddc, SCDC_TMDS_CONFIG, &val); + if (ret) + return ret; + + state->scrambling_enabled = val & SCDC_SCRAMBLING_ENABLE; + state->tmds_bclk_x40 = val & SCDC_TMDS_BIT_CLOCK_RATIO_BY_40; + + state->scrambling_detected = drm_scdc_get_scrambling_status(connector); + + ret = drm_scdc_read(ddc, SCDC_UPDATE_0, &upd_flags, sizeof(upd_flags)); + if (ret) + return ret; + + if (upd_flags[0] & SCDC_STATUS_UPDATE) { + ret = drm_scdc_read_status0_flags(connector, &state->stf); + if (ret) + return ret; + } + + if (upd_flags[0] & SCDC_CED_UPDATE) { + ret = drm_scdc_read_error_counters(connector, state->error_count); + if (ret) + return ret; + } + + return 0; +} +EXPORT_SYMBOL(drm_scdc_read_state); + +#define scdc_print_str(_f, key, s) \ + (seq_printf((_f), "%-30s: %s\n", (key), (s))) +#define scdc_print_flag(_f, key, val) \ + (scdc_print_str((_f), (key), str_yes_no((val)))) +#define scdc_print_dec(_f, key, val) \ + (seq_printf((_f), "%-30s: %d\n", (key), (val))) + +static int scdc_status_show(struct seq_file *m, void *data) +{ + struct scdc_debugfs_priv *priv = m->private; + struct drm_scdc_state *st = &priv->state; + struct drm_connector *connector = priv->connector; + struct drm_scdc *scdc = &connector->display_info.hdmi.scdc; + int ret; + + drm_connector_get(connector); + + if (connector->status != connector_status_connected) { + ret = -ENODEV; + goto err_conn_put; + } + + scdc_print_flag(m, "SCDC Supported", scdc->supported); + if (!scdc->supported) { + ret = 0; + goto err_conn_put; + } + + scdc_print_flag(m, "Sink Read Request Capable", scdc->read_request); + scdc_print_flag(m, "Scrambling Supported", scdc->scrambling.supported); + scdc_print_flag(m, "Low Rate Scrambling Supported", scdc->scrambling.low_rates); + + ret = drm_scdc_read_state(connector, st); + drm_connector_put(connector); + if (ret) + return ret; + + scdc_print_flag(m, "Scrambling Enabled", st->scrambling_enabled); + scdc_print_flag(m, "Scrambling Detected", st->scrambling_detected); + + if (st->tmds_bclk_x40) + scdc_print_str(m, "TMDS Bit Clock Ratio", "1/40"); + else + scdc_print_str(m, "TMDS Bit Clock Ratio", "1/10"); + + scdc_print_flag(m, "Clock Detected", st->stf.clock_detected); + scdc_print_flag(m, "Channel 0 Locked", st->stf.ch0_locked); + scdc_print_flag(m, "Channel 1 Locked", st->stf.ch1_locked); + scdc_print_flag(m, "Channel 2 Locked", st->stf.ch2_locked); + + scdc_print_dec(m, "Channel 0 Errors", st->error_count[0]); + scdc_print_dec(m, "Channel 1 Errors", st->error_count[1]); + scdc_print_dec(m, "Channel 2 Errors", st->error_count[2]); + + return 0; + +err_conn_put: + drm_connector_put(connector); + + return ret; +} +DEFINE_SHOW_ATTRIBUTE(scdc_status); + +/** + * drm_scdc_debugfs_init - Initialize scdc files in connector debugfs + * @connector: pointer to &struct drm_connector to operate on + * @root: debugfs &struct dentry for the debugfs root of @connector + * + * Creates SCDC-related debugfs files for @connector. Must be called after + * @root is already created. + */ +void drm_scdc_debugfs_init(struct drm_connector *connector, struct dentry *root) +{ + struct scdc_debugfs_priv *priv; + + if (!root || !connector) + return; + + priv = drmm_kzalloc(connector->dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return; + + priv->connector = connector; + + debugfs_create_file("scdc_status", 0444, root, priv, &scdc_status_fops); +} +EXPORT_SYMBOL(drm_scdc_debugfs_init); diff --git a/include/drm/display/drm_scdc_helper.h b/include/drm/display/drm_scdc_helper.h index e9ccaeba56dd..3b3a4e0e48ba 100644 --- a/include/drm/display/drm_scdc_helper.h +++ b/include/drm/display/drm_scdc_helper.h @@ -30,6 +30,31 @@ struct drm_connector; struct i2c_adapter; +struct dentry; + +struct drm_scdc_status_flags { + /* Status Register 0 */ + bool clock_detected; + bool ch0_locked; + bool ch1_locked; + bool ch2_locked; +}; + +struct drm_scdc_state { + /** @stf: contents of the status flag registers */ + struct drm_scdc_status_flags stf; + /** @scramling_enabled: true if TMDS scrambling is on */ + bool scrambling_enabled; + /** @scrambling_detected: true if the sink actually detected scrambling */ + bool scrambling_detected; + /** + * @tmds_bclk_x40: true if TMDS bit period is 1/40th of the TMDS + * clock period, false if it's 1/10th of the clock period. + */ + bool tmds_bclk_x40; + /** @error_count: character error counts for each channel */ + u16 error_count[3]; +}; int drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer, size_t size); @@ -77,4 +102,11 @@ bool drm_scdc_get_scrambling_status(struct drm_connector *connector); bool drm_scdc_set_scrambling(struct drm_connector *connector, bool enable); bool drm_scdc_set_high_tmds_clock_ratio(struct drm_connector *connector, bool set); +int drm_scdc_read_status0_flags(struct drm_connector *connector, + struct drm_scdc_status_flags *flags); +int drm_scdc_read_state(struct drm_connector *connector, + struct drm_scdc_state *state); +int drm_scdc_read_error_counters(struct drm_connector *connector, u16 counter[3]); +void drm_scdc_debugfs_init(struct drm_connector *connector, struct dentry *root); + #endif -- 2.54.0