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Thu, 03 Sep 2026 12:37:27 +0000 (UTC) From: Pierre Pinon To: Ville Syrjala Cc: Pierre Pinon , intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, stable@vger.kernel.org, Suraj Kandpal Subject: Re: [PATCH 1/2] drm/i915/cdclk: Avoid spurious cdclk sanitization on PTL+ Date: Thu, 3 Sep 2026 14:37:00 +0200 Message-ID: <20260903123706.543711-1-pierre@pinon1.fr> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260717155107.17801-1-ville.syrjala@linux.intel.com> References: <20260717155107.17801-1-ville.syrjala@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Proofpoint-ORIG-GUID: ItCIq1ivjgRzbeViCwG5F-tvMnf4y8E0 X-Proofpoint-GUID: ItCIq1ivjgRzbeViCwG5F-tvMnf4y8E0 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTAzMDEwOSBTYWx0ZWRfX8IaQWQ8Xc9cb mfvq42HfXVMG/bpMOEmibHn1p6/FMSZha5GolrOY7NMBQhI+CcTkfHU5kPBB0e+g/vU2uneyJSp 8OVXNAGNcYplPDzNG27F3vOAo30ZikoGJntkKCJVaG0jUQQFMUn2QJo/Z4LAGV+QeITcboKWhXr ZDA0anw+0yDY1CfAf6wUGKcdTI5wWZNmei7Mq9hyQXpquuQf42/e0vZd8Bv47HelDdk+FVaxhTi FFNscvSqmoKlBHXphNC2pUm1V7E5vwF3RLjHz3hsSU414oCeK/NI5qZLMM/kzp6hmwpHSaNmJjQ 6PeLcM5zXu0p/jlUq5Sfwiosw3Vq+eMWCPG4/XPQRgK9Klg4gJ22bjBDJKyQmY= X-Authority-Info-Out: v=2.4 cv=Gp1PO01C c=1 sm=1 tr=0 ts=6a996a0c cx=c_apl:c_pps:t_out a=oyWFxbOnq+dmhQrAPgaJYA==:117 a=oyWFxbOnq+dmhQrAPgaJYA==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=pGLkceISAAAA:8 a=IZRBV0DxEYK2dcOnbAcA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-JNJ: 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 R+HvMA9zag4V9y8zN3fkajdDpr6rt8SfmkhmenFvavwV8TuPuoiNjV6byHriimL3LM56RmA6nOeCB4eGmXHdLph7kDpPuNGvNyWKuhNYT7gb5jBFS9N3Xn8hxfiv0ZBK26GEywOFIbcUh0Vwes7Lla3XZP5tcK0CVr/XLbsTPWnj8rBtfdZZyrg1An/MdcgvWSLfZdnk9waqRH5AduE37Ht2RApKdt4iSFWObeKgucnGkJqInC7GtI8+iGmwyZpP94s0J89K4s/vil/AQ2u1b65Scp9wrtEjGpM/QPHl15KE7pa6GLoXMLvDT/dVrsRYke/v4aWglWNen+PVZChWr3Z7K+orcDB/Y X-Mailman-Approved-At: Thu, 03 Sep 2026 16:00:12 +0000 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 Fri, Jul 17, 2026 at 06:51:06PM +0300, Ville Syrjälä wrote: > Apparently PTL+ no longer has the cd2x pipe select field in > CDCLK_CTL. Take that into account during CDCLK sanitization. > > This currently triggers a spurious CDCLK sanitization during > driver load on PTL+ which will causes a visible glitch on all > active displays. Tested on a Panther Lake laptop (Intel Graphics [8086:b090], xe driver, internal eDP panel), Fedora 43. For what it is worth, on this machine the symptom is more than a glitch: the internal panel comes up corrupted on cold boot and stays corrupted until a suspend/resume cycle. dmesg shows: xe 0000:00:02.0: [drm] Selective fetch area calculation failed in pipe A xe 0000:00:02.0: [drm] *ERROR* CPU pipe A FIFO underrun xe 0000:00:02.0: [drm] *ERROR* CPU pipe A FIFO underrun Counting "CPU pipe A FIFO underrun" in dmesg across boots of the same machine: 6.17.1-300.fc43 unpatched 0 (unaffected) 7.1.12-100.fc43 unpatched 2 7.1.12 + this patch [*] patched 0 (4 boots) 7.1.13-100.fc43 unpatched 2 7.3.0-rc1 + this patch patched 0 [*] 7.1.x predates bxt_cdclk_cd2x_pipe_mask() and needs a slightly different form, see below; the 7.3.0-rc1 build carries this patch as posted, unmodified. With the patch the panel comes up clean from cold boot and the underruns are gone. Tested-by: Pierre Pinon This covers 1/2 only; I have not tested 2/2. Note the "Selective fetch area calculation failed in pipe A" drm_info_once is still printed with the patch applied. As far as I can tell that one is unrelated -- it is the deliberate full-update fallback in intel_psr2_sel_fetch_update() -- and harmless here. I realise this is already committed, so the tag may well arrive too late to be folded in. I am sending it anyway as a data point for the stable backport, which is the part that matters to me here: neither 7.1.y nor 7.2.y carries the fix yet. On 7.1.y the change does not apply as posted, since that tree predates bxt_cdclk_cd2x_pipe_mask(). The form I have been running there guards the two original lines instead: if (DISPLAY_VER(display) < 30) { cdctl &= ~bxt_cdclk_cd2x_pipe(display, INVALID_PIPE); cdctl |= bxt_cdclk_cd2x_pipe(display, INVALID_PIPE); } That is the variant covered by the four 7.1.12 boots above. The same form was posted independently by Chang Jiong as <20260816062344.796615-1-xspeed1989@gmail.com>, which I only noticed afterwards.