From patchwork Fri Sep 21 22:34:46 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brendan Higgins X-Patchwork-Id: 973479 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-i2c-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.b="E9cUG4ht"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 42H7hN3hWBz9s89 for ; Sat, 22 Sep 2018 08:35:00 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725977AbeIVEZy (ORCPT ); Sat, 22 Sep 2018 00:25:54 -0400 Received: from mail-qk1-f201.google.com ([209.85.222.201]:40239 "EHLO mail-qk1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725858AbeIVEZy (ORCPT ); Sat, 22 Sep 2018 00:25:54 -0400 Received: by mail-qk1-f201.google.com with SMTP id h199-v6so11353127qke.7 for ; Fri, 21 Sep 2018 15:34:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=3spB2NtTNh5Vjis2QKzdZ6kRMBSBYpWYy/wWr0qAAHI=; b=E9cUG4htpP/M9IrvZXE6fGeh3u4WQqmKQccblAiO1kkJliaLc10vb2wKovj9k4s/Jn uSt/kMXCAQn9vivhbOC0+Ev3GxlttASl4jY+dsjqVwoDgCt0Ri22Q08gk0SDo8FmIKP6 I6IKgF9N0d9VDWhw7MeefPy1yLYceHRq9FcoX6xNnyHGXR6oIInv9tnDHJ8X1QqPH3ko sNNMAgxUmIZPP0OXY20d+p9kdyvvy5DZwxAPpP9h+inLr677p/HDMcMskqYfVJi6hEWZ eOiIDLbiSFXx5P7tQFfYj9wy/ghUgOhnmEWq1I2mHgR7t4uzQfYdgAwsNDKveFIwnQDe ep6Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=3spB2NtTNh5Vjis2QKzdZ6kRMBSBYpWYy/wWr0qAAHI=; b=mTQ1ma0FG7kf9ZD6Pf8Ln93KouKT2YV5kgEse1Gkk5K5IWFsxKlULouoknqA/+WO7N JhN7OwDP6l1bmQTgYWE/2FZXBUY1FUWUDzAGwSltVxg2Kn9/4nFmknMStzLC0d3soSgQ q9BoXso6kVggLPTKNy3TjFRQC+noGCmUCOuXzHizn4kXjFNoSQwcDa26/iJ73G8mDgIc UYPumHWRz6TN09MGGYhoqXGHuc1xqu1vMDewx0XxjtfveBibRb/c+H6S2nuaSXChaRRw 3lBJNVgHlPfnjgWnGqvsZq171FwARCOjk66bicPNkXM2vD9WraEqccGmEIP+nVvKXZaV JFng== X-Gm-Message-State: APzg51AeDXz+KJL5XOnj0135HWIQ9OyHPbv6FsyqBmy3z92f5SfcEEtm L2lML3WMYnWFj4+K/WwJ2W4yg/YWM1+uPrthqceFXg== X-Google-Smtp-Source: ANB0VdZqb8oCxs2v2/oAQiY8uDb/rhK0zkDA9Ndogni6DAro2cHQBRz5mTPwYRiSD+CDm0AbJl83DtDCcsP8A8W9Vygw/Q== X-Received: by 2002:ac8:29fd:: with SMTP id 58-v6mr14809305qtt.6.1537569298150; Fri, 21 Sep 2018 15:34:58 -0700 (PDT) Date: Fri, 21 Sep 2018 15:34:46 -0700 Message-Id: <20180921223446.82685-1-brendanhiggins@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.19.0.444.g18242da7ef-goog Subject: [PATCH v3] i2c: aspeed: fix invalid clock parameters for very large divisors From: Brendan Higgins To: jae.hyun.yoo@linux.intel.com, benh@kernel.crashing.org, joel@jms.id.au, andrew@aj.id.au Cc: linux-i2c@vger.kernel.org, openbmc@lists.ozlabs.org, linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org, Brendan Higgins Sender: linux-i2c-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org The function that computes clock parameters from divisors did not respect the maximum size of the bitfields that the parameters were written to. This fixes the bug. This bug can be reproduced with (and this fix verified with) the test at: https://kunit-review.googlesource.com/c/linux/+/1035/ Discovered-by-KUnit: https://kunit-review.googlesource.com/c/linux/+/1035/ Signed-off-by: Brendan Higgins Reviewed-by: Jae Hyun Yoo --- - v2 updates the title of the patch, renames a local variable, and prints an error when the clock divider is clamped. - v3 adds a missing newline character for the new logging statement. --- drivers/i2c/busses/i2c-aspeed.c | 62 +++++++++++++++++++++++---------- 1 file changed, 43 insertions(+), 19 deletions(-) diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c index c258c4d9a4c0..a3bfec2c0694 100644 --- a/drivers/i2c/busses/i2c-aspeed.c +++ b/drivers/i2c/busses/i2c-aspeed.c @@ -142,7 +142,8 @@ struct aspeed_i2c_bus { /* Synchronizes I/O mem access to base. */ spinlock_t lock; struct completion cmd_complete; - u32 (*get_clk_reg_val)(u32 divisor); + u32 (*get_clk_reg_val)(struct device *dev, + u32 divisor); unsigned long parent_clk_frequency; u32 bus_frequency; /* Transaction state. */ @@ -705,16 +706,27 @@ static const struct i2c_algorithm aspeed_i2c_algo = { #endif /* CONFIG_I2C_SLAVE */ }; -static u32 aspeed_i2c_get_clk_reg_val(u32 clk_high_low_max, u32 divisor) +static u32 aspeed_i2c_get_clk_reg_val(struct device *dev, + u32 clk_high_low_mask, + u32 divisor) { - u32 base_clk, clk_high, clk_low, tmp; + u32 base_clk_divisor, clk_high_low_max, clk_high, clk_low, tmp; + + /* + * SCL_high and SCL_low represent a value 1 greater than what is stored + * since a zero divider is meaningless. Thus, the max value each can + * store is every bit set + 1. Since SCL_high and SCL_low are added + * together (see below), the max value of both is the max value of one + * them times two. + */ + clk_high_low_max = (clk_high_low_mask + 1) * 2; /* * The actual clock frequency of SCL is: * SCL_freq = APB_freq / (base_freq * (SCL_high + SCL_low)) * = APB_freq / divisor * where base_freq is a programmable clock divider; its value is - * base_freq = 1 << base_clk + * base_freq = 1 << base_clk_divisor * SCL_high is the number of base_freq clock cycles that SCL stays high * and SCL_low is the number of base_freq clock cycles that SCL stays * low for a period of SCL. @@ -724,47 +736,59 @@ static u32 aspeed_i2c_get_clk_reg_val(u32 clk_high_low_max, u32 divisor) * SCL_low = clk_low + 1 * Thus, * SCL_freq = APB_freq / - * ((1 << base_clk) * (clk_high + 1 + clk_low + 1)) + * ((1 << base_clk_divisor) * (clk_high + 1 + clk_low + 1)) * The documentation recommends clk_high >= clk_high_max / 2 and * clk_low >= clk_low_max / 2 - 1 when possible; this last constraint * gives us the following solution: */ - base_clk = divisor > clk_high_low_max ? + base_clk_divisor = divisor > clk_high_low_max ? ilog2((divisor - 1) / clk_high_low_max) + 1 : 0; - tmp = (divisor + (1 << base_clk) - 1) >> base_clk; - clk_low = tmp / 2; - clk_high = tmp - clk_low; - if (clk_high) - clk_high--; + if (base_clk_divisor > ASPEED_I2CD_TIME_BASE_DIVISOR_MASK) { + base_clk_divisor = ASPEED_I2CD_TIME_BASE_DIVISOR_MASK; + clk_low = clk_high_low_mask; + clk_high = clk_high_low_mask; + dev_err(dev, + "clamping clock divider: divider requested, %u, is greater than largest possible divider, %u.\n", + divisor, (1 << base_clk_divisor) * clk_high_low_max); + } else { + tmp = (divisor + (1 << base_clk_divisor) - 1) + >> base_clk_divisor; + clk_low = tmp / 2; + clk_high = tmp - clk_low; + + if (clk_high) + clk_high--; - if (clk_low) - clk_low--; + if (clk_low) + clk_low--; + } return ((clk_high << ASPEED_I2CD_TIME_SCL_HIGH_SHIFT) & ASPEED_I2CD_TIME_SCL_HIGH_MASK) | ((clk_low << ASPEED_I2CD_TIME_SCL_LOW_SHIFT) & ASPEED_I2CD_TIME_SCL_LOW_MASK) - | (base_clk & ASPEED_I2CD_TIME_BASE_DIVISOR_MASK); + | (base_clk_divisor + & ASPEED_I2CD_TIME_BASE_DIVISOR_MASK); } -static u32 aspeed_i2c_24xx_get_clk_reg_val(u32 divisor) +static u32 aspeed_i2c_24xx_get_clk_reg_val(struct device *dev, u32 divisor) { /* * clk_high and clk_low are each 3 bits wide, so each can hold a max * value of 8 giving a clk_high_low_max of 16. */ - return aspeed_i2c_get_clk_reg_val(16, divisor); + return aspeed_i2c_get_clk_reg_val(dev, GENMASK(2, 0), divisor); } -static u32 aspeed_i2c_25xx_get_clk_reg_val(u32 divisor) +static u32 aspeed_i2c_25xx_get_clk_reg_val(struct device *dev, u32 divisor) { /* * clk_high and clk_low are each 4 bits wide, so each can hold a max * value of 16 giving a clk_high_low_max of 32. */ - return aspeed_i2c_get_clk_reg_val(32, divisor); + return aspeed_i2c_get_clk_reg_val(dev, GENMASK(3, 0), divisor); } /* precondition: bus.lock has been acquired. */ @@ -777,7 +801,7 @@ static int aspeed_i2c_init_clk(struct aspeed_i2c_bus *bus) clk_reg_val &= (ASPEED_I2CD_TIME_TBUF_MASK | ASPEED_I2CD_TIME_THDSTA_MASK | ASPEED_I2CD_TIME_TACST_MASK); - clk_reg_val |= bus->get_clk_reg_val(divisor); + clk_reg_val |= bus->get_clk_reg_val(bus->dev, divisor); writel(clk_reg_val, bus->base + ASPEED_I2C_AC_TIMING_REG1); writel(ASPEED_NO_TIMEOUT_CTRL, bus->base + ASPEED_I2C_AC_TIMING_REG2);