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Fri, 18 Oct 2024 10:03:48 +0000 Received: from DB6PR07MB3509.eurprd07.prod.outlook.com ([fe80::5484:a966:1322:f78b]) by DB6PR07MB3509.eurprd07.prod.outlook.com ([fe80::5484:a966:1322:f78b%4]) with mapi id 15.20.8069.016; Fri, 18 Oct 2024 10:03:48 +0000 From: Wojciech Siudy To: linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, devicetree@vger.kernel.org Cc: andi.shyti@kernel.org, peda@axentia.se, Wojciech Siudy Subject: [PATCH v5 2/2] pca954x: Reset if channel select fails Date: Fri, 18 Oct 2024 12:03:38 +0200 Message-Id: <20241018100338.19420-3-wojciech.siudy@nokia.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20241018100338.19420-1-wojciech.siudy@nokia.com> References: <20241018100338.19420-1-wojciech.siudy@nokia.com> X-ClientProxiedBy: FR5P281CA0047.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:f0::10) To DB6PR07MB3509.eurprd07.prod.outlook.com (2603:10a6:6:21::16) Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DB6PR07MB3509:EE_|AM9PR07MB7139:EE_ X-MS-Office365-Filtering-Correlation-Id: 38690609-c82a-457d-3105-08dcef5c2915 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|10070799003|376014|1800799024; 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Without sending a reset pulse, a power-on-reset of the entire device would be required to restore communication. The datasheet specifies a minimum hold time of 4 ns for the reset pulse, but due to the path's capacitance and themux having its own clock, it is recommended to extend this to approximately 1 us. This option can be enabled using the i2c-mux-timeout-reset property in the device tree and should only be used if the reset line is not shared with other devices. Signed-off-by: Wojciech Siudy --- Changelog: v2: * Removed mail header from the commit log * Decreased reset pulse hold time from 10 to 1 ms v3: * Make this functionality enabled by appropriate property in devicetree v4: * Fix missing condition check from devicetree --- drivers/i2c/muxes/i2c-mux-pca954x.c | 51 ++++++++++++++++++++++------- 1 file changed, 40 insertions(+), 11 deletions(-) diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c index 6f84018258c4..316048b0011d 100644 --- a/drivers/i2c/muxes/i2c-mux-pca954x.c +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c @@ -110,6 +110,7 @@ struct pca954x { u8 last_chan; /* last register value */ /* MUX_IDLE_AS_IS, MUX_IDLE_DISCONNECT or >= 0 for channel */ s32 idle_state; + u8 timeout_reset; struct i2c_client *client; @@ -316,6 +317,30 @@ static u8 pca954x_regval(struct pca954x *data, u8 chan) return 1 << chan; } +static void pca954x_reset_deassert(struct pca954x *data) +{ + if (data->reset_cont) + reset_control_deassert(data->reset_cont); + else + gpiod_set_value_cansleep(data->reset_gpio, 0); +} + +static void pca954x_reset_assert(struct pca954x *data) +{ + if (data->reset_cont) + reset_control_assert(data->reset_cont); + else + gpiod_set_value_cansleep(data->reset_gpio, 1); +} + +static void pca954x_reset_mux(struct pca954x *data) +{ + dev_warn(&data->client->dev, "resetting the device\n"); + pca954x_reset_assert(data); + udelay(1); + pca954x_reset_deassert(data); +} + static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan) { struct pca954x *data = i2c_mux_priv(muxc); @@ -329,6 +354,9 @@ static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan) ret = pca954x_reg_write(muxc->parent, client, regval); data->last_chan = ret < 0 ? 0 : regval; } + if (ret == -ETIMEDOUT && (data->reset_cont || data->reset_gpio) && + data->timeout_reset) + pca954x_reset_mux(data); return ret; } @@ -338,6 +366,7 @@ static int pca954x_deselect_mux(struct i2c_mux_core *muxc, u32 chan) struct pca954x *data = i2c_mux_priv(muxc); struct i2c_client *client = data->client; s32 idle_state; + int ret = 0; idle_state = READ_ONCE(data->idle_state); if (idle_state >= 0) @@ -347,13 +376,16 @@ static int pca954x_deselect_mux(struct i2c_mux_core *muxc, u32 chan) if (idle_state == MUX_IDLE_DISCONNECT) { /* Deselect active channel */ data->last_chan = 0; - return pca954x_reg_write(muxc->parent, client, - data->last_chan); + ret = pca954x_reg_write(muxc->parent, client, data->last_chan); + if (ret == -ETIMEDOUT && + (data->reset_cont || data->reset_gpio) && + data->timeout_reset) + pca954x_reset_mux(data); } /* otherwise leave as-is */ - return 0; + return ret; } static ssize_t idle_state_show(struct device *dev, @@ -543,14 +575,6 @@ static int pca954x_get_reset(struct device *dev, struct pca954x *data) return 0; } -static void pca954x_reset_deassert(struct pca954x *data) -{ - if (data->reset_cont) - reset_control_deassert(data->reset_cont); - else - gpiod_set_value_cansleep(data->reset_gpio, 0); -} - /* * I2C init/probing/exit functions */ @@ -625,6 +649,11 @@ static int pca954x_probe(struct i2c_client *client) data->idle_state = MUX_IDLE_DISCONNECT; } + if (device_property_read_bool(dev, "i2c-mux-timeout-reset")) + data->timeout_reset = 1; + else + data->timeout_reset = 0; + /* * Write the mux register at addr to verify * that the mux is in fact present. This also