From nobody Mon Feb 9 01:44:57 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C7A566F068; Wed, 13 Mar 2024 16:37:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710347871; cv=none; b=tKM3h1+ILQd4t+MLIJvRA+9WSi3l70dE8jIEYjLDV46bbEVB+30Vyt5Sf/CahCHHVELausVYiMx1zuZH8YQpQul8kncpFgjRrpXdqLwSgUQvjGDz933Kfx7zv0Si1HcJglavkUbHTG6lD6eyowHewjjPnuI2X1oAboK/rmjPyKY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710347871; c=relaxed/simple; bh=gCc354VV2RHhC+3wRo+eHNpK+3QIIn//kY2xO+M8bo8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gnayeH4eVnPdKm/idlFbfV/Z+KX8o0QkClgdly45TJeaa3GO7v31UAphBAMPXsxMOVyduzuVYqdYClgVQ14h6Qak8+vsnI7k9h2JeTJBqvR6prK7zAABSEj2NWhKVGGwEfFPIkvOR82fx+zWXpNaCftPXKUJ+WGxvXEVdBSJROc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ICgqVFRl; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ICgqVFRl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CEC87C433C7; Wed, 13 Mar 2024 16:37:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1710347871; bh=gCc354VV2RHhC+3wRo+eHNpK+3QIIn//kY2xO+M8bo8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ICgqVFRlue/wFFOGET/d1sIfgv9QuC3OTgXggl9uMukOED1WolecD02CA/CMACmzR UAHxbs7h8RfmoXjxhtvwLGBl8skpKLAwSgLVd+nu1KyIw2Sb92QlRKL9poKPwPWyRJ Ovo/AYhoXk7G4RtOOWHygIPMVVullruwJU6yXTL+Fd7MKuR+oxzy2B6FjO9y41iwnk BBX+T2Cj4jh9cvhlLmP9J2HleiRXm2nA6GzUpI9tMBG56cml2DaGNxBjVvvRxILJrN KmHPSP3sWcO+m5txA+Nb6krMhxUPxOZCBmgKXxWePYbA7J2tJ4qx+hYM+ZvOr7Sske sx9+jpc9BI2cA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Tobias Jakobi (Compleo)" , Oleksij Rempel , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.6 33/60] net: dsa: microchip: fix register write order in ksz8_ind_write8() Date: Wed, 13 Mar 2024 12:36:40 -0400 Message-ID: <20240313163707.615000-34-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240313163707.615000-1-sashal@kernel.org> References: <20240313163707.615000-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-KernelTest-Patch: http://kernel.org/pub/linux/kernel/v6.x/stable-review/patch-6.6.22-rc1.gz X-KernelTest-Tree: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git X-KernelTest-Branch: linux-6.6.y X-KernelTest-Patches: git://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git X-KernelTest-Version: 6.6.22-rc1 X-KernelTest-Deadline: 2024-03-15T16:36+00:00 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: "Tobias Jakobi (Compleo)" [ Upstream commit b7fb7729c94fb2d23c79ff44f7a2da089c92d81c ] This bug was noticed while re-implementing parts of the kernel driver in userspace using spidev. The goal was to enable some of the errata workarounds that Microchip describes in their errata sheet [1]. Both the errata sheet and the regular datasheet of e.g. the KSZ8795 imply that you need to do this for indirect register accesses: - write a 16-bit value to a control register pair (this value consists of the indirect register table, and the offset inside the table) - either read or write an 8-bit value from the data storage register (indicated by REG_IND_BYTE in the kernel) The current implementation has the order swapped. It can be proven, by reading back some indirect register with known content (the EEE register modified in ksz8_handle_global_errata() is one of these), that this implementation does not work. Private discussion with Oleksij Rempel of Pengutronix has revealed that the workaround was apparantly never tested on actual hardware. [1] https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductD= ocuments/Errata/KSZ87xx-Errata-DS80000687C.pdf Signed-off-by: Tobias Jakobi (Compleo) Reviewed-by: Oleksij Rempel Fixes: 7b6e6235b664 ("net: dsa: microchip: ksz8795: handle eee specif errat= um") Link: https://lore.kernel.org/r/20240304154135.161332-1-tobias.jakobi.compl= eo@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/net/dsa/microchip/ksz8795.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/dsa/microchip/ksz8795.c b/drivers/net/dsa/microchi= p/ksz8795.c index 91aba470fb2fa..28d7ada3ec067 100644 --- a/drivers/net/dsa/microchip/ksz8795.c +++ b/drivers/net/dsa/microchip/ksz8795.c @@ -49,9 +49,9 @@ static int ksz8_ind_write8(struct ksz_device *dev, u8 tab= le, u16 addr, u8 data) mutex_lock(&dev->alu_mutex); =20 ctrl_addr =3D IND_ACC_TABLE(table) | addr; - ret =3D ksz_write8(dev, regs[REG_IND_BYTE], data); + ret =3D ksz_write16(dev, regs[REG_IND_CTRL_0], ctrl_addr); if (!ret) - ret =3D ksz_write16(dev, regs[REG_IND_CTRL_0], ctrl_addr); + ret =3D ksz_write8(dev, regs[REG_IND_BYTE], data); =20 mutex_unlock(&dev->alu_mutex); =20 --=20 2.43.0