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a="2022198" X-IronPort-AV: E=Sophos;i="6.27,184,1787036400"; d="scan'208";a="2022198" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by orvoesa107.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Oct 2026 06:57:13 -0700 X-CSE-ConnectionGUID: 3L6qMBxPQHGxrz9O4tQEmQ== X-CSE-MsgGUID: 3h8p5xRmSp6MI0Cr4QH+iA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,184,1787036400"; d="scan'208";a="5050203" Received: from ncintean-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.245.129]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Oct 2026 06:57:10 -0700 Date: Thu, 29 Oct 2026 15:57:07 +0200 From: Andy Shevchenko To: Antoine Pichot Cc: linux-media@vger.kernel.org, sakari.ailus@linux.intel.com, mchehab@kernel.org, hansg@kernel.org, dan.scally@ideasonboard.com, djrscally@gmail.com, dmanresa@gmail.com, dave.stevenson@raspberrypi.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2 1/9] media: i2c: ov7251: Use in-range PLL1 dividers for the 319.2 MHz link Message-ID: References: <20261028112154.855185-1-antoine.pichot@gmail.com> <20261028112154.855185-2-antoine.pichot@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261028112154.855185-2-antoine.pichot@gmail.com> Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo On Wed, Oct 28, 2026 at 08:21:46PM +0900, Antoine Pichot wrote: > The 19.2 MHz PLL1 table for the 319.2 MHz link frequency puts a > pre-divider of 1 before the multiplier of 133 and a divider of 4 after > it, so the PLL1 multiplier output (the VCO) runs at 19.2 x 133 = > 2553.6 MHz before being divided down to 638.4 MHz. The OV7750/OV7251 > datasheet (rev 2.12, table 2-11) limits it to 300 to 800 MHz. > > Use pre-divider 4 (register 0x30B4 = 0x04) and divider 1 (0x30B1 = > 0x01). The multiplier output is then 4.8 x 133 = 638.4 MHz, inside the > range, and the MIPI clock stays 638.4 Mbps, so the link frequency does > not change. The Windows driver programs these values for the Surface > Book 2's Windows Hello mode. > > On ACPI systems this table has been unreachable since it was added, > because ov7251_check_hwcfg() selects the wrong index. The next patch > fixes the index, so the two must go in together. With the index fix > alone, a Surface Pro 7+ (IPU6) had CSI-2 errors in 7 of 10 150-frame > runs, 3 of them stalls; with this change 0 of 13. A Surface Book 2 > (IPU3) streams clean with either table. Dave Stevenson measured on a > 24 MHz Raspberry Pi board that the out-of-range tables miss their > nominal frequency and proposed the same values. The 24 MHz tables are > left alone because nobody in the thread can test a change to them. > Fixes: ed9566ce1946 ("media: i2c: Add support for new frequencies to ov7251") > Cc: stable@vger.kernel.org > Link: https://lore.kernel.org/linux-media/6ae0e944.b6db0abd.16b13d.d261@mx.google.com/ > Link: https://lore.kernel.org/linux-media/CAPY8ntBFJJPg3y46gC=bNq_55QifC7mKmeq8+pAEDVN42fGUXw@mail.gmail.com/ These Links are not referred in the text above, make sure they are being referred, otherwise Linus T. becomes grumpy on this. On top, consider using Reported-by and Closes tags if applicable. ... Code wise LGTM (I followed the discussion). -- With Best Regards, Andy Shevchenko