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Thu, 13 Aug 2020 10:55:20 +0100 (BST) Received: from eusmtrp2.samsung.com (unknown [182.198.249.139]) by eucas1p2.samsung.com (KnoxPortal) with ESMTPA id 20200813095520eucas1p209432599420d62e0e54a5545334c329c~qy0YpIMZh1146911469eucas1p2t; Thu, 13 Aug 2020 09:55:20 +0000 (GMT) Received: from eusmgms1.samsung.com (unknown [182.198.249.179]) by eusmtrp2.samsung.com (KnoxPortal) with ESMTP id 20200813095520eusmtrp2fe4e9b5d47a39aa0810c3ed57fe67bea~qy0YoVe951763817638eusmtrp2Z; Thu, 13 Aug 2020 09:55:20 +0000 (GMT) X-AuditID: cbfec7f4-65dff7000000176d-79-5f350e080c68 Received: from eusmtip1.samsung.com ( [203.254.199.221]) by eusmgms1.samsung.com (EUCPMTA) with SMTP id CC.E2.06314.70E053F5; Thu, 13 Aug 2020 10:55:20 +0100 (BST) Received: from AMDC3061.digital.local (unknown [106.120.51.75]) by eusmtip1.samsung.com (KnoxPortal) with ESMTPA id 20200813095519eusmtip1dd85c2a532534f620e64589b11d3d65f~qy0YKPvHN3006430064eusmtip1_; Thu, 13 Aug 2020 09:55:19 +0000 (GMT) From: Sylwester Nawrocki To: linux-clk@vger.kernel.org Cc: tomasz.figa@gmail.com, cw00.choi@samsung.com, sboyd@kernel.org, mturquette@baylibre.com, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org, b.zolnierkie@samsung.com, m.szyprowski@samsung.com, Sylwester Nawrocki Subject: [PATCH v3] clk: samsung: Prevent potential endless loop in the PLL set_rate ops Date: Thu, 13 Aug 2020 11:55:08 +0200 Message-Id: <20200813095508.7563-1-s.nawrocki@samsung.com> X-Mailer: git-send-email 2.17.1 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrLIsWRmVeSWpSXmKPExsWy7djPc7ocfKbxBt9eCllsnLGe1eL6l+es Fh977rFaXN41h81ixvl9TBZrj9xlt7h4ytXi8Jt2Vot/1zayWKza9YfRgcvj/Y1Wdo+ds+6y e2xa1cnm0bdlFaPH501yAaxRXDYpqTmZZalF+nYJXBkzJ69gKdhiUjGhn6WB8aJWFyMnh4SA iUT3261sXYxcHEICKxglLi9aygrhfGGUeLroFguE85lRYvrk94wwLa+uP2GCSCxnlPjRfpMZ ruXXmTXsIFVsAoYSvUf7wDpEBGQlbh37CbaEWaCZSeJzfxMLSEJYIEri4bpnYDaLgKpE3+1L YA28AlYSsxdsYoVYJy+xesMBsA0SAq/ZJDZd+cgMkXCRWPf2CwuELSzx6vgWdghbRuL/zvlM EA3NjBI9u2+zQzgTGCXuH18A9YW1xJ1zv4Bu4gC6SVNi/S59EFNCwFHi61NGCJNP4sZbQZBi ZiBz0rbpzBBhXomONiGIGSoSv1dNZ4KwpSS6n/yHusZDouHTNbBrhARiJdo+rGaewCg3C2HV AkbGVYziqaXFuempxUZ5qeV6xYm5xaV56XrJ+bmbGIGJ4vS/4192MO76k3SIUYCDUYmHd8Iv 43gh1sSy4srcQ4wSHMxKIrxOZ0/HCfGmJFZWpRblxxeV5qQWH2KU5mBREuc1XvQyVkggPbEk NTs1tSC1CCbLxMEp1cAocJhJ68mKWLZrDCvfz4xX2T6ndSHXrAK200+277lw8flUlZvPXl5W 3G2rPyXg4NqITasvtF887Xh99R8g9dRi2d/E65nXl046bjVBaM+eqW/lE1ZJVZ+fZn16lbaO zIl+Yat/z76+Lqm9c9kzMtBBeb6czMk3rDdjv2iG1jyLWqwlbtB580mBEktxRqKhFnNRcSIA a1z/hRADAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrILMWRmVeSWpSXmKPExsVy+t/xu7ocfKbxBjOsLTbOWM9qcf3Lc1aL jz33WC0u75rDZjHj/D4mi7VH7rJbXDzlanH4TTurxb9rG1ksVu36w+jA5fH+Riu7x85Zd9k9 Nq3qZPPo27KK0ePzJrkA1ig9m6L80pJUhYz84hJbpWhDCyM9Q0sLPSMTSz1DY/NYKyNTJX07 m5TUnMyy1CJ9uwS9jJmTV7AUbDGpmNDP0sB4UauLkZNDQsBE4tX1J0xdjFwcQgJLGSW2Tm8A cjiAElIS81uUIGqEJf5c62KDqPnEKHFp9wpmkASbgKFE79E+RhBbREBW4taxn2BFzAK9TBLt 37ewgCSEBSIkJh28yA5iswioSvTdvgTWwCtgJTF7wSZWiA3yEqs3HGCewMizgJFhFaNIamlx bnpusaFecWJucWleul5yfu4mRmBwbjv2c/MOxksbgw8xCnAwKvHwTvhlHC/EmlhWXJl7iFGC g1lJhNfp7Ok4Id6UxMqq1KL8+KLSnNTiQ4ymQMsnMkuJJucDIyevJN7Q1NDcwtLQ3Njc2MxC SZy3Q+BgjJBAemJJanZqakFqEUwfEwenVAOj6NtlL3IOOdlLbVt1baECK0eLaFTlvnOyucrP fKpE+RQN1k3aflmxTEsnzlFw2fXFKj+Pbp8fu+3h2lf71n+bt1nqyG1zSdncVfmlIjy1Cw9L T/o4p++9HevbnRduT9U3qfyjWcL198dr1u89Z84dWugdv6drpqN8htlG47qstue7OHdZNAiZ KrEUZyQaajEXFScCAAQEVetkAgAA X-CMS-MailID: 20200813095520eucas1p209432599420d62e0e54a5545334c329c X-Msg-Generator: CA X-RootMTR: 20200813095520eucas1p209432599420d62e0e54a5545334c329c X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20200813095520eucas1p209432599420d62e0e54a5545334c329c References: Sender: linux-samsung-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org In the .set_rate callback for some PLLs there is a loop polling state of the PLL lock bit and it may become an endless loop when something goes wrong with the PLL. For some PLLs there is already code for polling with a timeout but it uses the ktime API, which doesn't work in some conditions when the set_rate op is called, in particular during initialization of the clk provider before the clocksource initialization has completed. Hence the ktime API cannot be used to reliably detect the PLL locking timeout. This patch adds a common helper function for busy waiting on the PLL lock bit with timeout detection. Actual PLL lock time depends on the P divider value, the VCO frequency and a constant PLL type specific LOCK_FACTOR and can be calculated as lock_time = Pdiv * LOCK_FACTOR / VCO_freq Common timeout value of 10 ms is used for all the PLLs with an assumption that maximum possible value of Pdiv is 64, maximum possible LOCK_FACTOR value is 3000 and minimum VCO frequency is 24 MHz. Signed-off-by: Sylwester Nawrocki Acked-by: Chanwoo Choi --- Changes for v3: - use busy-loop with udelay() instead of ktime API Changes for v2: - use common readl_relaxed_poll_timeout_atomic() macro --- drivers/clk/samsung/clk-pll.c | 94 ++++++++++++++++--------------------------- 1 file changed, 34 insertions(+), 60 deletions(-) -- 2.7.4 diff --git a/drivers/clk/samsung/clk-pll.c b/drivers/clk/samsung/clk-pll.c index ac70ad7..c83d261 100644 --- a/drivers/clk/samsung/clk-pll.c +++ b/drivers/clk/samsung/clk-pll.c @@ -15,7 +15,7 @@ #include "clk.h" #include "clk-pll.h" -#define PLL_TIMEOUT_MS 10 +#define PLL_TIMEOUT_US 10000U struct samsung_clk_pll { struct clk_hw hw; @@ -63,6 +63,25 @@ static long samsung_pll_round_rate(struct clk_hw *hw, return rate_table[i - 1].rate; } +static int samsung_pll_lock_wait(struct samsung_clk_pll *pll, + unsigned int reg_mask) +{ + int i; + + /* Wait until the PLL is in steady locked state */ + for (i = 0; i < PLL_TIMEOUT_US / 2; i++) { + if (readl_relaxed(pll->con_reg) & reg_mask) + return 0; + + udelay(2); + cpu_relax(); + } + + pr_err("Could not lock PLL %s\n", clk_hw_get_name(&pll->hw)); + + return -ETIMEDOUT; +} + static int samsung_pll3xxx_enable(struct clk_hw *hw) { struct samsung_clk_pll *pll = to_clk_pll(hw); @@ -241,12 +260,9 @@ static int samsung_pll35xx_set_rate(struct clk_hw *hw, unsigned long drate, writel_relaxed(tmp, pll->con_reg); /* Wait until the PLL is locked if it is enabled. */ - if (tmp & BIT(pll->enable_offs)) { - do { - cpu_relax(); - tmp = readl_relaxed(pll->con_reg); - } while (!(tmp & BIT(pll->lock_offs))); - } + if (tmp & BIT(pll->enable_offs)) + return samsung_pll_lock_wait(pll, BIT(pll->lock_offs)); + return 0; } @@ -318,7 +334,7 @@ static int samsung_pll36xx_set_rate(struct clk_hw *hw, unsigned long drate, unsigned long parent_rate) { struct samsung_clk_pll *pll = to_clk_pll(hw); - u32 tmp, pll_con0, pll_con1; + u32 pll_con0, pll_con1; const struct samsung_pll_rate_table *rate; rate = samsung_get_pll_settings(pll, drate); @@ -356,13 +372,8 @@ static int samsung_pll36xx_set_rate(struct clk_hw *hw, unsigned long drate, pll_con1 |= rate->kdiv << PLL36XX_KDIV_SHIFT; writel_relaxed(pll_con1, pll->con_reg + 4); - /* wait_lock_time */ - if (pll_con0 & BIT(pll->enable_offs)) { - do { - cpu_relax(); - tmp = readl_relaxed(pll->con_reg); - } while (!(tmp & BIT(pll->lock_offs))); - } + if (pll_con0 & BIT(pll->enable_offs)) + return samsung_pll_lock_wait(pll, BIT(pll->lock_offs)); return 0; } @@ -437,7 +448,6 @@ static int samsung_pll45xx_set_rate(struct clk_hw *hw, unsigned long drate, struct samsung_clk_pll *pll = to_clk_pll(hw); const struct samsung_pll_rate_table *rate; u32 con0, con1; - ktime_t start; /* Get required rate settings from table */ rate = samsung_get_pll_settings(pll, drate); @@ -489,20 +499,7 @@ static int samsung_pll45xx_set_rate(struct clk_hw *hw, unsigned long drate, writel_relaxed(con0, pll->con_reg); /* Wait for locking. */ - start = ktime_get(); - while (!(readl_relaxed(pll->con_reg) & PLL45XX_LOCKED)) { - ktime_t delta = ktime_sub(ktime_get(), start); - - if (ktime_to_ms(delta) > PLL_TIMEOUT_MS) { - pr_err("%s: could not lock PLL %s\n", - __func__, clk_hw_get_name(hw)); - return -EFAULT; - } - - cpu_relax(); - } - - return 0; + return samsung_pll_lock_wait(pll, PLL45XX_LOCKED); } static const struct clk_ops samsung_pll45xx_clk_ops = { @@ -588,7 +585,6 @@ static int samsung_pll46xx_set_rate(struct clk_hw *hw, unsigned long drate, struct samsung_clk_pll *pll = to_clk_pll(hw); const struct samsung_pll_rate_table *rate; u32 con0, con1, lock; - ktime_t start; /* Get required rate settings from table */ rate = samsung_get_pll_settings(pll, drate); @@ -648,20 +644,7 @@ static int samsung_pll46xx_set_rate(struct clk_hw *hw, unsigned long drate, writel_relaxed(con1, pll->con_reg + 0x4); /* Wait for locking. */ - start = ktime_get(); - while (!(readl_relaxed(pll->con_reg) & PLL46XX_LOCKED)) { - ktime_t delta = ktime_sub(ktime_get(), start); - - if (ktime_to_ms(delta) > PLL_TIMEOUT_MS) { - pr_err("%s: could not lock PLL %s\n", - __func__, clk_hw_get_name(hw)); - return -EFAULT; - } - - cpu_relax(); - } - - return 0; + return samsung_pll_lock_wait(pll, PLL46XX_LOCKED); } static const struct clk_ops samsung_pll46xx_clk_ops = { @@ -1035,14 +1018,9 @@ static int samsung_pll2550xx_set_rate(struct clk_hw *hw, unsigned long drate, (rate->sdiv << PLL2550XX_S_SHIFT); writel_relaxed(tmp, pll->con_reg); - /* wait_lock_time */ - do { - cpu_relax(); - tmp = readl_relaxed(pll->con_reg); - } while (!(tmp & (PLL2550XX_LOCK_STAT_MASK - << PLL2550XX_LOCK_STAT_SHIFT))); - - return 0; + /* Wait for locking. */ + return samsung_pll_lock_wait(pll, + PLL2550XX_LOCK_STAT_MASK << PLL2550XX_LOCK_STAT_SHIFT); } static const struct clk_ops samsung_pll2550xx_clk_ops = { @@ -1132,13 +1110,9 @@ static int samsung_pll2650x_set_rate(struct clk_hw *hw, unsigned long drate, con1 |= ((rate->kdiv & PLL2650X_K_MASK) << PLL2650X_K_SHIFT); writel_relaxed(con1, pll->con_reg + 4); - do { - cpu_relax(); - con0 = readl_relaxed(pll->con_reg); - } while (!(con0 & (PLL2650X_LOCK_STAT_MASK - << PLL2650X_LOCK_STAT_SHIFT))); - - return 0; + /* Wait for locking. */ + return samsung_pll_lock_wait(pll, + PLL2650X_LOCK_STAT_MASK << PLL2650X_LOCK_STAT_SHIFT); } static const struct clk_ops samsung_pll2650x_clk_ops = {