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[109.252.192.57]) by smtp.gmail.com with ESMTPSA id k11sm2572079lji.95.2020.12.15.13.11.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Dec 2020 13:11:58 -0800 (PST) From: Dmitry Osipenko To: Thierry Reding , Jonathan Hunter , Peter De Schrijver , Prashant Gaikwad , Michael Turquette , Stephen Boyd Cc: linux-tegra@vger.kernel.org, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v1 2/3] clk: tegra: Fix refcounting of gate clocks Date: Wed, 16 Dec 2020 00:11:49 +0300 Message-Id: <20201215211150.21214-3-digetx@gmail.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201215211150.21214-1-digetx@gmail.com> References: <20201215211150.21214-1-digetx@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org The refcounting of the gate clocks has a bug causing the enable_refcnt to underflow when unused clocks are disabled. This happens because clk provider erroneously bumps the refcount if clock is enabled at a boot time, which it shouldn't be doing, and it does this only for the gate clocks, while peripheral clocks are using the same gate ops and the peripheral clocks are missing the initial bump. Hence the refcount of the peripheral clocks is 0 when unused clocks are disabled and then the counter is decremented further by the gate ops, causing the integer underflow. Fix this problem by removing the erroneous bump and by implementing the disable_unused() callback, which disables the unused gates properly. The visible effect of the bug is such that the unused clocks are never gated if a loaded kernel module grabs the unused clocks and starts to use them. In practice this shouldn't cause any real problems for the drivers and boards supported by the kernel today. Signed-off-by: Dmitry Osipenko --- drivers/clk/tegra/clk-periph-gate.c | 72 +++++++++++++++++++---------- drivers/clk/tegra/clk-periph.c | 11 +++++ 2 files changed, 58 insertions(+), 25 deletions(-) diff --git a/drivers/clk/tegra/clk-periph-gate.c b/drivers/clk/tegra/clk-periph-gate.c index 4b31beefc9fc..3c4259fec82e 100644 --- a/drivers/clk/tegra/clk-periph-gate.c +++ b/drivers/clk/tegra/clk-periph-gate.c @@ -48,18 +48,9 @@ static int clk_periph_is_enabled(struct clk_hw *hw) return state; } -static int clk_periph_enable(struct clk_hw *hw) +static void clk_periph_enable_locked(struct clk_hw *hw) { struct tegra_clk_periph_gate *gate = to_clk_periph_gate(hw); - unsigned long flags = 0; - - spin_lock_irqsave(&periph_ref_lock, flags); - - gate->enable_refcnt[gate->clk_num]++; - if (gate->enable_refcnt[gate->clk_num] > 1) { - spin_unlock_irqrestore(&periph_ref_lock, flags); - return 0; - } write_enb_set(periph_clk_to_bit(gate), gate); udelay(2); @@ -78,6 +69,32 @@ static int clk_periph_enable(struct clk_hw *hw) udelay(1); writel_relaxed(0, gate->clk_base + LVL2_CLK_GATE_OVRE); } +} + +static void clk_periph_disable_locked(struct clk_hw *hw) +{ + struct tegra_clk_periph_gate *gate = to_clk_periph_gate(hw); + + /* + * If peripheral is in the APB bus then read the APB bus to + * flush the write operation in apb bus. This will avoid the + * peripheral access after disabling clock + */ + if (gate->flags & TEGRA_PERIPH_ON_APB) + tegra_read_chipid(); + + write_enb_clr(periph_clk_to_bit(gate), gate); +} + +static int clk_periph_enable(struct clk_hw *hw) +{ + struct tegra_clk_periph_gate *gate = to_clk_periph_gate(hw); + unsigned long flags = 0; + + spin_lock_irqsave(&periph_ref_lock, flags); + + if (!gate->enable_refcnt[gate->clk_num]++) + clk_periph_enable_locked(hw); spin_unlock_irqrestore(&periph_ref_lock, flags); @@ -91,21 +108,28 @@ static void clk_periph_disable(struct clk_hw *hw) spin_lock_irqsave(&periph_ref_lock, flags); - gate->enable_refcnt[gate->clk_num]--; - if (gate->enable_refcnt[gate->clk_num] > 0) { - spin_unlock_irqrestore(&periph_ref_lock, flags); - return; - } + WARN_ON(!gate->enable_refcnt[gate->clk_num]); + + if (gate->enable_refcnt[gate->clk_num]-- == 1) + clk_periph_disable_locked(hw); + + spin_unlock_irqrestore(&periph_ref_lock, flags); +} + +static void clk_periph_disable_unused(struct clk_hw *hw) +{ + struct tegra_clk_periph_gate *gate = to_clk_periph_gate(hw); + unsigned long flags = 0; + + spin_lock_irqsave(&periph_ref_lock, flags); /* - * If peripheral is in the APB bus then read the APB bus to - * flush the write operation in apb bus. This will avoid the - * peripheral access after disabling clock + * Some clocks are duplicated and some of them are marked as critical, + * like fuse and fuse_burn for example, thus the enable_refcnt will + * be non-zero here id the "unused" duplicate is disabled by CCF. */ - if (gate->flags & TEGRA_PERIPH_ON_APB) - tegra_read_chipid(); - - write_enb_clr(periph_clk_to_bit(gate), gate); + if (!gate->enable_refcnt[gate->clk_num]) + clk_periph_disable_locked(hw); spin_unlock_irqrestore(&periph_ref_lock, flags); } @@ -114,6 +138,7 @@ const struct clk_ops tegra_clk_periph_gate_ops = { .is_enabled = clk_periph_is_enabled, .enable = clk_periph_enable, .disable = clk_periph_disable, + .disable_unused = clk_periph_disable_unused, }; struct clk *tegra_clk_register_periph_gate(const char *name, @@ -148,9 +173,6 @@ struct clk *tegra_clk_register_periph_gate(const char *name, gate->enable_refcnt = enable_refcnt; gate->regs = pregs; - if (read_enb(gate) & periph_clk_to_bit(gate)) - enable_refcnt[clk_num]++; - /* Data in .init is copied by clk_register(), so stack variable OK */ gate->hw.init = &init; diff --git a/drivers/clk/tegra/clk-periph.c b/drivers/clk/tegra/clk-periph.c index 67620c7ecd9e..79ca3aa072b7 100644 --- a/drivers/clk/tegra/clk-periph.c +++ b/drivers/clk/tegra/clk-periph.c @@ -100,6 +100,15 @@ static void clk_periph_disable(struct clk_hw *hw) gate_ops->disable(gate_hw); } +static void clk_periph_disable_unused(struct clk_hw *hw) +{ + struct tegra_clk_periph *periph = to_clk_periph(hw); + const struct clk_ops *gate_ops = periph->gate_ops; + struct clk_hw *gate_hw = &periph->gate.hw; + + gate_ops->disable_unused(gate_hw); +} + static void clk_periph_restore_context(struct clk_hw *hw) { struct tegra_clk_periph *periph = to_clk_periph(hw); @@ -126,6 +135,7 @@ const struct clk_ops tegra_clk_periph_ops = { .is_enabled = clk_periph_is_enabled, .enable = clk_periph_enable, .disable = clk_periph_disable, + .disable_unused = clk_periph_disable_unused, .restore_context = clk_periph_restore_context, }; @@ -135,6 +145,7 @@ static const struct clk_ops tegra_clk_periph_nodiv_ops = { .is_enabled = clk_periph_is_enabled, .enable = clk_periph_enable, .disable = clk_periph_disable, + .disable_unused = clk_periph_disable_unused, .restore_context = clk_periph_restore_context, }; -- 2.29.2