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Sun, 27 Oct 2024 11:50:02 +0000 Received: from DB9PR04MB8461.eurprd04.prod.outlook.com ([fe80::b1b9:faa9:901b:c197]) by DB9PR04MB8461.eurprd04.prod.outlook.com ([fe80::b1b9:faa9:901b:c197%5]) with mapi id 15.20.8069.016; Sun, 27 Oct 2024 11:50:02 +0000 From: "Peng Fan (OSS)" Date: Sun, 27 Oct 2024 20:00:07 +0800 Subject: [PATCH v3 1/5] clk: imx: lpcg-scu: SW workaround for errata (e10858) Message-Id: <20241027-imx-clk-v1-v3-1-89152574d1d7@nxp.com> References: <20241027-imx-clk-v1-v3-0-89152574d1d7@nxp.com> In-Reply-To: <20241027-imx-clk-v1-v3-0-89152574d1d7@nxp.com> To: Abel Vesa , Michael Turquette , Stephen Boyd , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Aisheng Dong Cc: linux-clk@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Abel Vesa , Peng Fan X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1730030419; l=3213; i=peng.fan@nxp.com; s=20230812; h=from:subject:message-id; bh=aeiGOFthGwsWpWxLMDzbGyOzHOzdaByvU+6qeurmvKg=; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?q?6qPhfoKKQZml8SqdeGXiMMZzWVJR?= =?utf-8?q?Tc5OR+JjZPDqqM3j9e/r9zup7ceExKhKqNWeBRbS/7S6zKB4DpAqYZmWOH1GMZfPs?= =?utf-8?q?ISfV8WbZjX5eTa2Grmx2baKwT2RgzUo9Exm5eXlvUq+o7EEQQjgHfpM/REtOPJH/M?= =?utf-8?q?VD6viJ+FG0eAxuzWOZODLUYRBnlNXd+wt8dW7jqa0hF+hNFyiuSJVMIg26xyhcHkH?= =?utf-8?q?t9sdrbxU2Dn7NWUStAXanEOMDYAFWPXaT7OWWeuX7SH4zNWiKibg/h+njqUnyOyAs?= =?utf-8?q?2FgzEzHidJTsHX4iBYJYYY4uYI2bCpGhHMFDx9BwIToqN5DW5Ahq6rwpS8snSzvBs?= =?utf-8?q?XjN+C1GN8S/+2g8R4y6QCZT0v2HglNDGmlS+o6LxX2hB+iSZwFzOR1YeXwH82WO7v?= =?utf-8?q?PVofCkXWO6qmJxoU8Ckr2Xq8aUYCftwPxWH+UJD4d4Fh2uD0p49Tc1FC6RW8Oru5/?= =?utf-8?q?WaAeXvm7rFMg3ttvVB2WlQ6iIcxpw0YbsynROA0GvCXsJuPGFVlEirZcN6/gWpp6g?= =?utf-8?q?/V2syw0QOwCfgfC5vrirauKpQMNqs1dxhQdJO6cIyBZk4ELIGXdwzZ7vDpG34R5mg?= =?utf-8?q?ovBbs8xq4kA0u3isDayBbYydk6Y38hstMbYrukGfb0TmbIptokHiO88Sk8GshAYMb?= =?utf-8?q?2SELhS8AOWom/U3RwO5Zttg99RIiR1PbbOIOw+0UFH8YigoIykRy4CmHIarJUsfU3?= =?utf-8?q?Bddxv01aftXfCyqmLNluHpJwMRiu6rbhqmzqQ2rW3CVMyMWkMWP2cJUISbny9+yeG?= =?utf-8?q?Ps3p5+d16vCbOfzHVwED7z55daxrivp6v0Xb7b76Y9TxK3C//CDMCr1sS+ruwNNda?= =?utf-8?q?tVw3dwY1kYFn86aflw6cOUY6TWDdAY1Z7l/R6INMPQEWg9ZnAQlbZKuEc9gXZ6mvJ?= =?utf-8?q?niJXMxiyvj2zibzD9x7tcei2EQsDtf2+zCP5RwEmWc8UtU7NzLTQWMgA8sOKqcdUo?= =?utf-8?q?zzhDgOxboP/+taNXJJB328C42MQ2+SY8SVm93EvSE0Ehp3mOmXGE0R5NBEUy4dXmy?= =?utf-8?q?exV9mPgLRkbujsIGqvKtZ6r4/TXNRKbPaP87lMtt3lGm8ShHY8/el7+tobcuAHR9b?= =?utf-8?q?MO/JaobESHGinq94YZ2ZDsJ/39xTuCtVE0gm3x2JymIdoPMEfzeXVHQH3Uu/zoh7U?= =?utf-8?q?xYiO9zoXbArUW+utl36FmzL/O46sTu3E8yg+lhydKF8T6gaQZ+awI+V6b7mAV0o43?= =?utf-8?q?VxFa2ntJnu9zaeUh/zqJnVuTwINfsKnMaJjQLGf4qFDJbD0kwcU9J7bRu5X67jAVa?= =?utf-8?q?73ihSfBWa9wyL5t2lsSAcDW8+LctU14qUEEMWpmQaCenKMq/HfQSSQzfSsBZCw3xS?= =?utf-8?q?Syn2mLqwojojl/uWJdb0kUWCOMRXH6smFKAMEKpm+Wtn2eWGgkJPz1CErDwfBmLFw?= =?utf-8?q?UyIbXAu5/h93ALXyqpUDUw3MqJyrkC5L77Yc9PkotyeMSS+1UTCm7zd3HjIi/6Eek?= =?utf-8?q?LSnbporaDMP+K2iMkwk6W2PSYUQlMK9uXLvOBGUnhe2OIElug1f6UZbXOeHJgyUdP?= =?utf-8?q?+osTDrs6lNoZ?= X-OriginatorOrg: oss.nxp.com X-MS-Exchange-CrossTenant-Network-Message-Id: 5edc3ae5-c936-45df-0d52-08dcf67d7dcc X-MS-Exchange-CrossTenant-AuthSource: DB9PR04MB8461.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Oct 2024 11:50:02.2554 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 20iqOMZO8yp2NpUobal8ACgcrWJZLG088iEMr6zuWYa4Lid4p2hYyLhbcc1fgzSy9KIg4V9OdfyNboOJxzKWpg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS8PR04MB8689 From: Peng Fan Back-to-back LPCG writes can be ignored by the LPCG register due to a HW bug. The writes need to be separated by at least 4 cycles of the gated clock. See https://www.nxp.com.cn/docs/en/errata/IMX8_1N94W.pdf The workaround is implemented as follows: 1. For clocks running greater than or equal to 24MHz, a read followed by the write will provide sufficient delay. 2. For clocks running below 24MHz, add a delay of 4 clock cylces after the write to the LPCG register. Fixes: 2f77296d3df9 ("clk: imx: add lpcg clock support") Signed-off-by: Peng Fan --- drivers/clk/imx/clk-lpcg-scu.c | 37 +++++++++++++++++++++++++++++-------- 1 file changed, 29 insertions(+), 8 deletions(-) diff --git a/drivers/clk/imx/clk-lpcg-scu.c b/drivers/clk/imx/clk-lpcg-scu.c index dd5abd09f3e206a5073767561b517d5b3320b28c..620afdf8dc03e9564bb074ca879cf778f7fc6419 100644 --- a/drivers/clk/imx/clk-lpcg-scu.c +++ b/drivers/clk/imx/clk-lpcg-scu.c @@ -6,10 +6,12 @@ #include #include +#include #include #include #include #include +#include #include "clk-scu.h" @@ -41,6 +43,29 @@ struct clk_lpcg_scu { #define to_clk_lpcg_scu(_hw) container_of(_hw, struct clk_lpcg_scu, hw) +/* e10858 -LPCG clock gating register synchronization errata */ +static void lpcg_e10858_writel(unsigned long rate, void __iomem *reg, u32 val) +{ + writel(val, reg); + + if (rate >= 24 * HZ_PER_MHZ || rate == 0) { + /* + * The time taken to access the LPCG registers from the AP core + * through the interconnect is longer than the minimum delay + * of 4 clock cycles required by the errata. + * Adding a readl will provide sufficient delay to prevent + * back-to-back writes. + */ + readl(reg); + } else { + /* + * For clocks running below 24MHz, wait a minimum of + * 4 clock cycles. + */ + ndelay(4 * (DIV_ROUND_UP(1000 * HZ_PER_MHZ, rate))); + } +} + static int clk_lpcg_scu_enable(struct clk_hw *hw) { struct clk_lpcg_scu *clk = to_clk_lpcg_scu(hw); @@ -57,7 +82,8 @@ static int clk_lpcg_scu_enable(struct clk_hw *hw) val |= CLK_GATE_SCU_LPCG_HW_SEL; reg |= val << clk->bit_idx; - writel(reg, clk->reg); + + lpcg_e10858_writel(clk_hw_get_rate(hw), clk->reg, reg); spin_unlock_irqrestore(&imx_lpcg_scu_lock, flags); @@ -74,7 +100,7 @@ static void clk_lpcg_scu_disable(struct clk_hw *hw) reg = readl_relaxed(clk->reg); reg &= ~(CLK_GATE_SCU_LPCG_MASK << clk->bit_idx); - writel(reg, clk->reg); + lpcg_e10858_writel(clk_hw_get_rate(hw), clk->reg, reg); spin_unlock_irqrestore(&imx_lpcg_scu_lock, flags); } @@ -145,13 +171,8 @@ static int __maybe_unused imx_clk_lpcg_scu_resume(struct device *dev) { struct clk_lpcg_scu *clk = dev_get_drvdata(dev); - /* - * FIXME: Sometimes writes don't work unless the CPU issues - * them twice - */ - - writel(clk->state, clk->reg); writel(clk->state, clk->reg); + lpcg_e10858_writel(0, clk->reg, clk->state); dev_dbg(dev, "restore lpcg state 0x%x\n", clk->state); return 0;