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 10032C87FD3 for ; Wed, 6 Aug 2025 13:27:07 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 9EA8810E784; Wed, 6 Aug 2025 13:27:06 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="R+gbzRDz"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.15]) by gabe.freedesktop.org (Postfix) with ESMTPS id 796CD10E77D for ; Wed, 6 Aug 2025 13:27:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1754486826; x=1786022826; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=DyTVDL97ulWHbGzlWwEqn/hwhDZ1KY7M2BhdNIVY7Wk=; b=R+gbzRDzbYHc1KJfuEERIR+8pfoTk7hRpbsUNA6mTOyYH/6g/n3FX8uy P25cwCE0Ag2jPq7bwrXC0+H5pTzPqqCbgj+SOJ/S/i9ibKG8IYJ/Y10fl 5Fddu/HCxoe8a2vN4j35NtGNhGt7J1ygsuVHLLN11jX+Z7a6LHNXof66Q UIhpkdhDN2Uq6scKTtKPyoUQroml6r1s6ycJJcs2cKkKBrDrXeMRGxmwv /ySsk3XlDc1n6BH05JVyPVuRZRx4rAEcuGeVYIGwIihCn0pgBrnkPsYAO TnVR8WWj8ukTSAgbZbpwwVFUMXQSMQCr/YEer7tmtsMIl1u/Bt1eRLFVs w==; X-CSE-ConnectionGUID: uGeo/mf8T6ehDzhLrHEW4g== X-CSE-MsgGUID: RcJNRoITRHmSknlvzPwZTw== X-IronPort-AV: E=McAfee;i="6800,10657,11514"; a="56940606" X-IronPort-AV: E=Sophos;i="6.17,268,1747724400"; d="scan'208";a="56940606" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by fmvoesa109.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Aug 2025 06:27:05 -0700 X-CSE-ConnectionGUID: AyJoDNh+TZmpskefr1iOTQ== X-CSE-MsgGUID: isYPrAz3QhS/uEB2djI1iQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.17,268,1747724400"; d="scan'208";a="165111974" Received: from slindbla-desk.ger.corp.intel.com (HELO localhost) ([10.245.246.70]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Aug 2025 06:27:03 -0700 From: Jani Nikula To: Lee Shawn C , intel-gfx@lists.freedesktop.org Cc: Lee Shawn C , Shankar Uma Subject: Re: [PATCH] drm/i915/hdmi: add debugfs to contorl HDMI bpc In-Reply-To: <20250806042053.3570558-1-shawn.c.lee@intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <20250806042053.3570558-1-shawn.c.lee@intel.com> Date: Wed, 06 Aug 2025 16:27:00 +0300 Message-ID: <9503b1adc378ede3229835038307ab7eeb59571a@intel.com> MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Wed, 06 Aug 2025, Lee Shawn C wrote: > While performing HDMI compliance testing, test equipment may request > different bpc output for signal measurement. However, display driver > typically determines the maximum available bpc based on HW bandwidth. > > This patch introduces a new debugfs that allow user to configure Please don't refer to "this patch" in a commit message. Just "Introduce ...". *allows > dedicated bpc manually, and making HDMI compliance test much easier. > > Cc: Shankar Uma > Signed-off-by: Lee Shawn C > --- > .../drm/i915/display/intel_display_debugfs.c | 58 +++++++++++++++++++ > .../drm/i915/display/intel_display_types.h | 2 + > drivers/gpu/drm/i915/display/intel_hdmi.c | 7 +++ > 3 files changed, 67 insertions(+) > > diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c > index ce3f9810c42d..cca115a6f130 100644 > --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c > +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c > @@ -1208,6 +1208,56 @@ static const struct file_operations i915_dsc_fractional_bpp_fops = { > .write = i915_dsc_fractional_bpp_write > }; > > +static int i915_hdmi_req_bpc_show(struct seq_file *m, void *data) > +{ > + struct intel_connector *connector = m->private; > + > + seq_printf(m, "request bpc: %u\n", connector->force_hdmi_bpc); IMO there's no need to print "request bpc: " prefix. It just makes using the interface harder for userspace. > + > + return 0; > +} > + > +static ssize_t i915_hdmi_req_bpc_write(struct file *file, > + const char __user *ubuf, > + size_t len, loff_t *offp) > +{ > + struct seq_file *m = file->private_data; > + struct intel_connector *intel_connector = m->private; Just connector, not intel_connector for naming. > + struct intel_display *display = to_intel_display(intel_connector); > + int new_bpc = 0, ret = 0; No need for the initialization. > + char *kbuf; > + const char *p; > + > + kbuf = memdup_user_nul(ubuf, len); > + if (IS_ERR(kbuf)) > + return PTR_ERR(kbuf); > + > + p = strim(kbuf); > + > + ret = kstrtoint(p, 0, &new_bpc); > + if (ret < 0) > + return -EINVAL; Drop all of the above, and just use kstrtoint_from_user(). > + > + switch (new_bpc) { > + case 0: > + case 8: > + case 10: > + case 12: > + break; > + default: > + drm_dbg(display->drm, > + "HDMI bpc (%u) may exceed the max value (12)\n", new_bpc); Not sure if the message is required, but drm_dbg_kms() and just say the value is invalid. Consider passing, say, 5, and getting message: HDMI bpc (5) may exceed the max value (12) Not helpful, is it? > + return -EINVAL; > + } > + > + intel_connector->force_hdmi_bpc = new_bpc; > + > + *offp += len; > + kfree(kbuf); > + return len; > +} > +DEFINE_SHOW_STORE_ATTRIBUTE(i915_hdmi_req_bpc); > + > /* > * Returns the Current CRTC's bpc. > * Example usage: cat /sys/kernel/debug/dri/0/crtc-0/i915_current_bpc > @@ -1359,6 +1409,13 @@ void intel_connector_debugfs_add(struct intel_connector *connector) > connector_type == DRM_MODE_CONNECTOR_HDMIB) > debugfs_create_file("i915_lpsp_capability", 0444, root, > connector, &i915_lpsp_capability_fops); > + > + if (connector_type == DRM_MODE_CONNECTOR_HDMIA || > + connector_type == DRM_MODE_CONNECTOR_HDMIB) { > + connector->force_hdmi_bpc = 0; Unnecessary. > + debugfs_create_file("i915_force_hdmi_bpc", 0644, root, Please use "intel_force_bpc". We're moving away from i915 naming for display, and there's no need to make it HDMI only. We can start off with making the *implementation* HDMI only, and only registering it for HDMI, but let's keep the door open for amending it for other connector types in the future. > + connector, &i915_hdmi_req_bpc_fops); Ditto, intel_hdmi_force_bpc_fops. > + } > } > > /** > diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h > index 4d9df803ad47..e1e42d701f68 100644 > --- a/drivers/gpu/drm/i915/display/intel_display_types.h > +++ b/drivers/gpu/drm/i915/display/intel_display_types.h > @@ -564,6 +564,8 @@ struct intel_connector { > struct work_struct modeset_retry_work; > > struct intel_hdcp hdcp; > + > + u8 force_hdmi_bpc; int > }; > > struct intel_digital_connector_state { > diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c > index cbee628eb26b..0aa4044e2854 100644 > --- a/drivers/gpu/drm/i915/display/intel_hdmi.c > +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c > @@ -2118,6 +2118,7 @@ static int intel_hdmi_compute_bpc(struct intel_encoder *encoder, > int clock, bool respect_downstream_limits) > { > struct intel_hdmi *intel_hdmi = enc_to_intel_hdmi(encoder); > + struct intel_connector *intel_connector = intel_hdmi->attached_connector; Just connector, not intel_connector, is the current style. > int bpc; > > /* > @@ -2134,6 +2135,12 @@ static int intel_hdmi_compute_bpc(struct intel_encoder *encoder, > if (!respect_downstream_limits) > bpc = 8; > > + /* > + * overwrite bpc per user's request > + */ Useless comment. > + if (intel_connector->force_hdmi_bpc) > + bpc = intel_connector->force_hdmi_bpc; > + > for (; bpc >= 8; bpc -= 2) { > int tmds_clock = intel_hdmi_tmds_clock(clock, bpc, > crtc_state->sink_format); -- Jani Nikula, Intel