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[2a01:c23:c07d:2d00:ad78:a407:846a:969b]) by smtp.googlemail.com with ESMTPSA id a640c23a62f3a-a7248825d4bsm217402866b.207.2024.06.24.13.05.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Jun 2024 13:05:24 -0700 (PDT) Message-ID: <9183dfda-d3f3-4fa1-9a4b-c6edeb30482d@gmail.com> Date: Mon, 24 Jun 2024 22:06:16 +0200 Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 5/6] i2c: smbus: Support DDR5 SPD EEPROMs To: Wolfram Sang , Guenter Roeck , Armin Wolf , linux-hwmon@vger.kernel.org, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, Krzysztof Kozlowski , =?UTF-8?Q?Ren=C3=A9_Rebe?= , =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= , Stephen Horvath References: <20240604040237.1064024-1-linux@roeck-us.net> <20240604040237.1064024-6-linux@roeck-us.net> <79f406ae-cfc9-48bb-9c80-20f998c40b69@roeck-us.net> Content-Language: en-US From: Heiner Kallweit Autocrypt: addr=hkallweit1@gmail.com; keydata= xsFNBF/0ZFUBEAC0eZyktSE7ZNO1SFXL6cQ4i4g6Ah3mOUIXSB4pCY5kQ6OLKHh0FlOD5/5/ sY7IoIouzOjyFdFPnz4Bl3927ClT567hUJJ+SNaFEiJ9vadI6vZm2gcY4ExdIevYHWe1msJF MVE4yNwdS+UsPeCF/6CQQTzHc+n7DomE7fjJD5J1hOJjqz2XWe71fTvYXzxCFLwXXbBiqDC9 dNqOe5odPsa4TsWZ09T33g5n2nzTJs4Zw8fCy8rLqix/raVsqr8fw5qM66MVtdmEljFaJ9N8 /W56qGCp+H8Igk/F7CjlbWXiOlKHA25mPTmbVp7VlFsvsmMokr/imQr+0nXtmvYVaKEUwY2g 86IU6RAOuA8E0J5bD/BeyZdMyVEtX1kT404UJZekFytJZrDZetwxM/cAH+1fMx4z751WJmxQ J7mIXSPuDfeJhRDt9sGM6aRVfXbZt+wBogxyXepmnlv9K4A13z9DVLdKLrYUiu9/5QEl6fgI kPaXlAZmJsQfoKbmPqCHVRYj1lpQtDM/2/BO6gHASflWUHzwmBVZbS/XRs64uJO8CB3+V3fa cIivllReueGCMsHh6/8wgPAyopXOWOxbLsZ291fmZqIR0L5Y6b2HvdFN1Xhc+YrQ8TKK+Z4R mJRDh0wNQ8Gm89g92/YkHji4jIWlp2fwzCcx5+lZCQ1XdqAiHQARAQABzSZIZWluZXIgS2Fs bHdlaXQgPGhrYWxsd2VpdDFAZ21haWwuY29tPsLBjgQTAQgAOBYhBGxfqY/yOyXjyjJehXLe ig9U8DoMBQJf9GRVAhsDBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAAAoJEHLeig9U8DoMSycQ AJbfg8HZEK0ljV4M8nvdaiNixWAufrcZ+SD8zhbxl8GispK4F3Yo+20Y3UoZ7FcIidJWUUJL axAOkpI/70YNhlqAPMsuudlAieeYZKjIv1WV5ucNZ3VJ7dC+dlVqQdAr1iD869FZXvy91KhJ wYulyCf+s4T9YgmLC6jLMBZghKIf1uhSd0NzjyCqYWbk2ZxByZHgunEShOhHPHswu3Am0ftt ePaYIHgZs+Vzwfjs8I7EuW/5/f5G9w1vibXxtGY/GXwgGGHRDjFM7RSprGOv4F5eMGh+NFUJ TU9N96PQYMwXVxnQfRXl8O6ffSVmFx4H9rovxWPKobLmqQL0WKLLVvA/aOHCcMKgfyKRcLah 57vGC50Ga8oT2K1g0AhKGkyJo7lGXkMu5yEs0m9O+btqAB261/E3DRxfI1P/tvDZpLJKtq35 dXsj6sjvhgX7VxXhY1wE54uqLLHY3UZQlmH3QF5t80MS7/KhxB1pO1Cpcmkt9hgyzH8+5org +9wWxGUtJWNP7CppY+qvv3SZtKJMKsxqk5coBGwNkMms56z4qfJm2PUtJQGjA65XWdzQACib 2iaDQoBqGZfXRdPT0tC1H5kUJuOX4ll1hI/HBMEFCcO8++Bl2wcrUsAxLzGvhINVJX2DAQaF aNetToazkCnzubKfBOyiTqFJ0b63c5dqziAgzsFNBF/0ZFUBEADF8UEZmKDl1w/UxvjeyAeX kghYkY3bkK6gcIYXdLRfJw12GbvMioSguvVzASVHG8h7NbNjk1yur6AONfbUpXKSNZ0skV8V fG+ppbaY+zQofsSMoj5gP0amwbwvPzVqZCYJai81VobefTX2MZM2Mg/ThBVtGyzV3NeCpnBa 8AX3s9rrX2XUoCibYotbbxx9afZYUFyflOc7kEpc9uJXIdaxS2Z6MnYLHsyVjiU6tzKCiVOU KJevqvzPXJmy0xaOVf7mhFSNQyJTrZpLa+tvB1DQRS08CqYtIMxRrVtC0t0LFeQGly6bOngr ircurWJiJKbSXVstLHgWYiq3/GmCSx/82ObeLO3PftklpRj8d+kFbrvrqBgjWtMH4WtK5uN5 1WJ71hWJfNchKRlaJ3GWy8KolCAoGsQMovn/ZEXxrGs1ndafu47yXOpuDAozoHTBGvuSXSZo ythk/0EAuz5IkwkhYBT1MGIAvNSn9ivE5aRnBazugy0rTRkVggHvt3/7flFHlGVGpBHxFUwb /a4UjJBPtIwa4tWR8B1Ma36S8Jk456k2n1id7M0LQ+eqstmp6Y+UB+pt9NX6t0Slw1NCdYTW gJezWTVKF7pmTdXszXGxlc9kTrVUz04PqPjnYbv5UWuDd2eyzGjrrFOsJEi8OK2d2j4FfF++ AzOMdW09JVqejQARAQABwsF2BBgBCAAgFiEEbF+pj/I7JePKMl6Fct6KD1TwOgwFAl/0ZFUC GwwACgkQct6KD1TwOgxUfg//eAoYc0Vm4NrxymfcY30UjHVD0LgSvU8kUmXxil3qhFPS7KA+ y7tgcKLHOkZkXMX5MLFcS9+SmrAjSBBV8omKoHNo+kfFx/dUAtz0lot8wNGmWb+NcHeKM1eb nwUMOEa1uDdfZeKef/U/2uHBceY7Gc6zPZPWgXghEyQMTH2UhLgeam8yglyO+A6RXCh+s6ak Wje7Vo1wGK4eYxp6pwMPJXLMsI0ii/2k3YPEJPv+yJf90MbYyQSbkTwZhrsokjQEaIfjrIk3 rQRjTve/J62WIO28IbY/mENuGgWehRlTAbhC4BLTZ5uYS0YMQCR7v9UGMWdNWXFyrOB6PjSu Trn9MsPoUc8qI72mVpxEXQDLlrd2ijEWm7Nrf52YMD7hL6rXXuis7R6zY8WnnBhW0uCfhajx q+KuARXC0sDLztcjaS3ayXonpoCPZep2Bd5xqE4Ln8/COCslP7E92W1uf1EcdXXIrx1acg21 H/0Z53okMykVs3a8tECPHIxnre2UxKdTbCEkjkR4V6JyplTS47oWMw3zyI7zkaadfzVFBxk2 lo/Tny+FX1Azea3Ce7oOnRUEZtWSsUidtIjmL8YUQFZYm+JUIgfRmSpMFq8JP4VH43GXpB/S OCrl+/xujzvoUBFV/cHKjEQYBxo+MaiQa1U54ykM2W4DnHb1UiEf5xDkFd4= In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 12.06.2024 18:19, Wolfram Sang wrote: > > CCing Heiner... > >>>>> Yes, maybe this could be simplified to "(LP)DDR memory types" >>>>> >>>> >>>> I rephrased it to "Only works for (LP)DDR memory types up to DDR5". >>> >>> Thanks! >>> >>>> How about "Only works on systems with 1 to 8 memory slots" ? >>> >>> This is a question for Heiner. I'd think it is is still correct, but I >>> don't know exactly. >>> >> >> My interpretation was that it should work if the DIMMs are connected to >> multiplexed I2C busses, but probably not if they are connected to >> different adapters. The error message in that case is a bit misleading, >> though, because it claims that "More than 8 memory slots on a single bus", >> which isn't necessarily the case. For example, it should be perfectly valid >> to have up to 24 DIMMs in this system. >> >> i2c-0/name:SMBus PIIX4 adapter port 0 at 0b00 >> i2c-1/name:SMBus PIIX4 adapter port 2 at 0b00 >> i2c-2/name:SMBus PIIX4 adapter port 1 at 0b20 >> >> ... but I guess that is a question for someone with such a system to answer. >> >> Ultimately the handling of systems with more than 8 memory slots will need >> to be updated at some point. On my systems, with 'i2c: piix4: Register SPDs' >> applied, I see >> >> i2c i2c-0: 4/4 memory slots populated (from DMI) >> [my system is running 6.6.y which still generates that message] >> i2c i2c-0: Successfully instantiated SPD at 0x50 >> i2c i2c-0: Successfully instantiated SPD at 0x51 >> i2c i2c-0: Successfully instantiated SPD at 0x52 >> i2c i2c-0: Successfully instantiated SPD at 0x53 >> i2c i2c-1: 4/4 memory slots populated (from DMI) >> i2c i2c-2: 4/4 memory slots populated (from DMI) >> >> meaning the function is called for each adapter (which makes sense). >> However, the code counting the DIMMs doesn't really take the adapter >> into account, meaning adapters 1 and 2 are still probed even though >> all DIMMs were already instantiated from adapter 0. >> >> On a system with more than 8 DIMMs connected to different piix4 adapters >> (without mux) we'd probably see something like >> >> i2c i2c-0: More than 8 memory slots on a single bus, contact i801 maintainer ... >> i2c i2c-1: More than 8 memory slots on a single bus, contact i801 maintainer ... >> i2c i2c-2: More than 8 memory slots on a single bus, contact i801 maintainer ... >> >> which wouldn't be very helpful. I think the main problem may be that >> the i801 driver implements sub-adapters as muxes, but the piix4 driver >> doesn't do (or need) that. The message is also i801 centric which doesn't >> apply anymore after 'i2c: piix4: Register SPDs' is applied. >> >> However, I would not want to even try changing that code without access >> to a system using piix4 and supporting more than 8 memory slots. >> >> Thanks, >> Guenter >> >> It seems Intel systems never have more than one i801 SMBUS adapter, therefore systems with more than 8 memory slots have to use muxing. The current code was developed for the Intel use case, and therefore doesn't consider that a system may have dedicated SMBUS controllers per 8 memory slots. So support for this scenario has to be added.