From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932967AbeCSMp4 (ORCPT ); Mon, 19 Mar 2018 08:45:56 -0400 Received: from mail-eopbgr10101.outbound.protection.outlook.com ([40.107.1.101]:55008 "EHLO EUR02-HE1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932892AbeCSMps (ORCPT ); Mon, 19 Mar 2018 08:45:48 -0400 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=peda@axentia.se; Subject: Re: [PATCH linux dev-4.16] drivers: i2c: master arbiter: create driver To: Ken Chen , linux@roeck-us.net, wsa@the-dreams.de, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Cc: joel@jms.id.au References: <20180319113808.23485-1-chen.kenyy@inventec.com> From: Peter Rosin Organization: Axentia Technologies AB Message-ID: Date: Mon, 19 Mar 2018 13:45:39 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180319113808.23485-1-chen.kenyy@inventec.com> Content-Type: text/plain; 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I would have liked this subject: i2c: muxes: pca9641: new driver On 2018-03-19 12:38, Ken Chen wrote: > Initial PCA9641 2 chennel I2C bus master arbiter channel > with separate implementation. It has probe issue > and difference device hehavior between PCA9541 behavior > and PCA9641 in original PCA9641 patch. > > Signed-off-by: Ken Chen > --- > drivers/i2c/muxes/Kconfig | 9 + > drivers/i2c/muxes/Makefile | 1 + > drivers/i2c/muxes/i2c-mux-pca9641.c | 360 ++++++++++++++++++++++++++++++++++++ Given the big similarities between this and the pca9541 driver, I would very much prefer if you could extend that driver instead of making an almost-copy like this. I have added some comments below anyway, but most of them are irrelevant given that I want this merged with the pca9541 driver. But maybe Guenter feels differently about that merge? > 3 files changed, 370 insertions(+) > create mode 100644 drivers/i2c/muxes/i2c-mux-pca9641.c > > diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig > index 52a4a92..f9c51b8 100644 > --- a/drivers/i2c/muxes/Kconfig > +++ b/drivers/i2c/muxes/Kconfig > @@ -73,6 +73,15 @@ config I2C_MUX_PCA954x > This driver can also be built as a module. If so, the module > will be called i2c-mux-pca954x. > > +config I2C_MUX_PCA9641 > + tristate "NXP PCA9641 I2C Master demultiplexer" > + help > + If you say yes here you get support for the NXP PCA9641 > + I2C Master demultiplexer with an arbiter function. > + > + This driver can also be built as a module. If so, the module > + will be called i2c-mux-pca9641. > + > config I2C_MUX_PINCTRL > tristate "pinctrl-based I2C multiplexer" > depends on PINCTRL > diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile > index 6d9d865..a229a1a 100644 > --- a/drivers/i2c/muxes/Makefile > +++ b/drivers/i2c/muxes/Makefile > @@ -12,6 +12,7 @@ obj-$(CONFIG_I2C_MUX_LTC4306) += i2c-mux-ltc4306.o > obj-$(CONFIG_I2C_MUX_MLXCPLD) += i2c-mux-mlxcpld.o > obj-$(CONFIG_I2C_MUX_PCA9541) += i2c-mux-pca9541.o > obj-$(CONFIG_I2C_MUX_PCA954x) += i2c-mux-pca954x.o > +obj-$(CONFIG_I2C_MUX_PCA9641) += i2c-mux-pca9641.o > obj-$(CONFIG_I2C_MUX_PINCTRL) += i2c-mux-pinctrl.o > obj-$(CONFIG_I2C_MUX_REG) += i2c-mux-reg.o > > diff --git a/drivers/i2c/muxes/i2c-mux-pca9641.c b/drivers/i2c/muxes/i2c-mux-pca9641.c > new file mode 100644 > index 0000000..bcf45c8 > --- /dev/null > +++ b/drivers/i2c/muxes/i2c-mux-pca9641.c > @@ -0,0 +1,360 @@ > +/* > + * I2C demultiplexer driver for PCA9641 bus master demultiplexer > + * > + * Copyright (c) 2010 Ericsson AB. > + * > + * Author: Ken Chen A bit rich to claim to be the sole author, when you clearly "just" modified the pca9541 driver. Please state the history! > + * > + * Derived from: Maybe you intended to add something here, but forgot? > + * > + * This file is licensed under the terms of the GNU General Public > + * License version 2. This program is licensed "as is" without any > + * warranty of any kind, whether express or implied. > + */ > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +#include What is this last include for? We have moved away from specifying platform data in (new) code. > + > +/* > + * The PCA9641 is two I2C bus masters demultiplexer. It supports two I2C masters "is two I2C bus masters" -> "is a two I2C bus master" > + * connected to a single slave bus. > + * > + * It is designed for high reliability dual master I2C bus applications where > + * correct system operation is required, even when two I2C master issue their > + * commands at the same time. The arbiter will select a winner and let it work > + * uninterrupted, and the losing master will take control of the I2C bus after > + * the winnter has finished. The arbiter also allows for queued requests where winner > + * a master requests the downstream bus while the other master has control. > + * > + */ > + > +#define PCA9641_ID 0x01 > +#define PCA9641_ID_MAGIC 0x38 > + > +#define PCA9641_CONTROL 0x01 > +#define PCA9641_STATUS 0x02 > +#define PCA9641_TIME 0x03 > + > +#define PCA9641_CTL_LOCK_REQ BIT(0) > +#define PCA9641_CTL_LOCK_GRANT BIT(1) > +#define PCA9641_CTL_BUS_CONNECT BIT(2) > +#define PCA9641_CTL_BUS_INIT BIT(3) > +#define PCA9641_CTL_SMBUS_SWRST BIT(4) > +#define PCA9641_CTL_IDLE_TIMER_DIS BIT(5) > +#define PCA9641_CTL_SMBUS_DIS BIT(6) > +#define PCA9641_CTL_PRIORITY BIT(7) > + > +#define PCA9641_STS_OTHER_LOCK BIT(0) > +#define PCA9641_STS_BUS_INIT_FAIL BIT(1) > +#define PCA9641_STS_BUS_HUNG BIT(2) > +#define PCA9641_STS_MBOX_EMPTY BIT(3) > +#define PCA9641_STS_MBOX_FULL BIT(4) > +#define PCA9641_STS_TEST_INT BIT(5) > +#define PCA9641_STS_SCL_IO BIT(6) > +#define PCA9641_STS_SDA_IO BIT(7) > + > +#define PCA9641_RES_TIME 0x03 > + > +#define busoff(x, y) (!((x) & PCA9641_CTL_LOCK_GRANT) && \ > + !((y) & PCA9641_STS_OTHER_LOCK)) > +#define other_lock(x) ((x) & PCA9641_STS_OTHER_LOCK) > +#define lock_grant(x) ((x) & PCA9641_CTL_LOCK_GRANT) > + > +/* arbitration timeouts, in jiffies */ > +#define ARB_TIMEOUT (HZ / 8) /* 125 ms until forcing bus ownership */ > +#define ARB2_TIMEOUT (HZ / 4) /* 250 ms until acquisition failure */ > + > +/* arbitration retry delays, in us */ > +#define SELECT_DELAY_SHORT 50 > +#define SELECT_DELAY_LONG 1000 > + > +struct pca9641 { > + struct i2c_client *client; > + unsigned long select_timeout; > + unsigned long arb_timeout; > +}; > + > +static const struct i2c_device_id pca9641_id[] = { > + {"pca9641", 0}, > + {} > +}; > + > +MODULE_DEVICE_TABLE(i2c, pca9641_id); > + > +#ifdef CONFIG_OF > +static const struct of_device_id pca9641_of_match[] = { > + { .compatible = "nxp,pca9641" }, You need to describe the DT binding in Documentation/devicetree/bindings/i2c See nxp,pca9541.txt for inspiration. > + {} > +}; > +#endif > + > +/* > + * Write to chip register. Don't use i2c_transfer()/i2c_smbus_xfer() > + * as they will try to lock the adapter a second time. > + */ > +static int pca9641_reg_write(struct i2c_client *client, u8 command, u8 val) > +{ > + struct i2c_adapter *adap = client->adapter; > + int ret; > + > + if (adap->algo->master_xfer) { > + struct i2c_msg msg; > + char buf[2]; > + > + msg.addr = client->addr; > + msg.flags = 0; > + msg.len = 2; > + buf[0] = command; > + buf[1] = val; > + msg.buf = buf; > + ret = __i2c_transfer(adap, &msg, 1); > + } else { > + union i2c_smbus_data data; > + > + data.byte = val; > + ret = adap->algo->smbus_xfer(adap, client->addr, > + client->flags, > + I2C_SMBUS_WRITE, > + command, > + I2C_SMBUS_BYTE_DATA, &data); > + } > + > + return ret; > +} > + > +/* > + * Read from chip register. Don't use i2c_transfer()/i2c_smbus_xfer() > + * as they will try to lock adapter a second time. > + */ > +static int pca9641_reg_read(struct i2c_client *client, u8 command) > +{ > + struct i2c_adapter *adap = client->adapter; > + int ret; > + u8 val; > + > + if (adap->algo->master_xfer) { > + struct i2c_msg msg[2] = { > + { > + .addr = client->addr, > + .flags = 0, > + .len = 1, > + .buf = &command > + }, > + { > + .addr = client->addr, > + .flags = I2C_M_RD, > + .len = 1, > + .buf = &val > + } > + }; > + ret = __i2c_transfer(adap, msg, 2); > + if (ret == 2) > + ret = val; > + else if (ret >= 0) > + ret = -EIO; > + } else { > + union i2c_smbus_data data; > + > + ret = adap->algo->smbus_xfer(adap, client->addr, > + client->flags, > + I2C_SMBUS_READ, > + command, > + I2C_SMBUS_BYTE_DATA, &data); > + if (!ret) > + ret = data.byte; > + } > + return ret; > +} > + > +/* > + * Arbitration management functions > + */ > +static void pca9641_release_bus(struct i2c_client *client) > +{ > + pca9641_reg_write(client, PCA9641_CONTROL, 0); > +} > + > +/* > + * Channel arbitration > + * > + * Return values: > + * <0: error > + * 0 : bus not acquired > + * 1 : bus acquired > + */ > +static int pca9641_arbitrate(struct i2c_client *client) > +{ > + struct i2c_mux_core *muxc = i2c_get_clientdata(client); > + struct pca9641 *data = i2c_mux_priv(muxc); > + int reg_ctl, reg_sts; > + > + reg_ctl = pca9641_reg_read(client, PCA9641_CONTROL); > + if (reg_ctl < 0) > + return reg_ctl; > + reg_sts = pca9641_reg_read(client, PCA9641_STATUS); > + > + if (busoff(reg_ctl, reg_sts)) { > + /* > + * Bus is off. Request ownership or turn it on unless > + * other master requested ownership. > + */ > + reg_ctl |= PCA9641_CTL_LOCK_REQ; > + pca9641_reg_write(client, PCA9641_CONTROL, reg_ctl); > + reg_ctl = pca9641_reg_read(client, PCA9641_CONTROL); > + > + if (lock_grant(reg_ctl)) { > + /* > + * Other master did not request ownership, > + * or arbitration timeout expired. Take the bus. > + */ > + reg_ctl |= PCA9641_CTL_BUS_CONNECT \ > + | PCA9641_CTL_LOCK_REQ; > + pca9641_reg_write(client, PCA9641_CONTROL, reg_ctl); > + data->select_timeout = SELECT_DELAY_SHORT; > + > + return 1; > + } else { > + /* > + * Other master requested ownership. > + * Set extra long timeout to give it time to acquire it. > + */ > + data->select_timeout = SELECT_DELAY_LONG * 2; > + } > + } else if (lock_grant(reg_ctl)) { > + /* > + * Bus is on, and we own it. We are done with acquisition. > + */ > + reg_ctl |= PCA9641_CTL_BUS_CONNECT | PCA9641_CTL_LOCK_REQ; > + pca9641_reg_write(client, PCA9641_CONTROL, reg_ctl); > + > + return 1; > + } else if (other_lock(reg_sts)) { > + /* > + * Other master owns the bus. > + * If arbitration timeout has expired, force ownership. > + * Otherwise request it. > + */ > + data->select_timeout = SELECT_DELAY_LONG; > + reg_ctl |= PCA9641_CTL_LOCK_REQ; > + pca9641_reg_write(client, PCA9641_CONTROL, reg_ctl); > + } > + return 0; > +} > + > +static int pca9641_select_chan(struct i2c_mux_core *muxc, u32 chan) > +{ > + struct pca9641 *data = i2c_mux_priv(muxc); > + struct i2c_client *client = data->client; > + int ret; > + unsigned long timeout = jiffies + ARB2_TIMEOUT; > + /* give up after this time */ > + > + data->arb_timeout = jiffies + ARB_TIMEOUT; > + /* force bus ownership after this time */ > + > + do { > + ret = pca9641_arbitrate(client); > + if (ret) > + return ret < 0 ? ret : 0; > + > + if (data->select_timeout == SELECT_DELAY_SHORT) > + udelay(data->select_timeout); > + else > + msleep(data->select_timeout / 1000); > + } while (time_is_after_eq_jiffies(timeout)); > + > + return -ETIMEDOUT; > +} > + > +static int pca9641_release_chan(struct i2c_mux_core *muxc, u32 chan) > +{ > + struct pca9641 *data = i2c_mux_priv(muxc); > + struct i2c_client *client = data->client; > + > + pca9641_release_bus(client); > + return 0; > +} > + > +/* > + * I2C init/probing/exit functions > + */ > +static int pca9641_probe(struct i2c_client *client, > + const struct i2c_device_id *id) > +{ > + struct i2c_adapter *adap = client->adapter; > + struct pca954x_platform_data *pdata = dev_get_platdata(&client->dev); > + struct i2c_mux_core *muxc; > + struct pca9641 *data; > + int force; > + int ret; > + > + if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE_DATA)) > + return -ENODEV; Reading the data sheet, I noticed that the chip supports I2C device id. There's a brand new function available in -next [1] that allows you to check this. See the pca954x driver in -next for an example [2]. It checks the I2C device id for the newer pca984x chips. [1] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/i2c/i2c-core-base.c i2c_get_device_id(), currently circa line 2000 [2] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/i2c/muxes/i2c-mux-pca954x.c > + /* > + * I2C accesses are unprotected here. > + * We have to lock the adapter before releasing the bus. > + */ > + i2c_lock_adapter(adap); > + pca9641_release_bus(client); > + i2c_unlock_adapter(adap); > + > + /* Create mux adapter */ > + > + force = 0; > + if (pdata) > + force = pdata->modes[0].adap_id; > + muxc = i2c_mux_alloc(adap, &client->dev, 8, sizeof(*data), Why 8? Should be 1, no? > + I2C_MUX_ARBITRATOR, > + pca9641_select_chan, pca9641_release_chan); > + if (!muxc) > + return -ENOMEM; > + > + data = i2c_mux_priv(muxc); > + data->client = client; > + > + i2c_set_clientdata(client, muxc); > + > + Lose one of the empty lines here. > + ret = i2c_mux_add_adapter(muxc, force, 0, 0); > + if (ret) { > + dev_err(&client->dev, "failed to register master demultiplexer\n"); This dev_err should go. i2c_mux_add_adapter provides a more detailed error message on failure. Cheers, Peter > + return ret; > + } > + > + dev_info(&client->dev, "registered master demultiplexer for I2C %s\n", > + client->name); > + > + return 0; > +} > + > +static int pca9641_remove(struct i2c_client *client) > +{ > + struct i2c_mux_core *muxc = i2c_get_clientdata(client); > + > + i2c_mux_del_adapters(muxc); > + return 0; > +} > + > +static struct i2c_driver pca9641_driver = { > + .driver = { > + .name = "pca9641", > + .of_match_table = of_match_ptr(pca9641_of_match), > + }, > + .probe = pca9641_probe, > + .remove = pca9641_remove, > + .id_table = pca9641_id, > +}; > + > +module_i2c_driver(pca9641_driver); > + > +MODULE_AUTHOR("Ken Chen "); > +MODULE_DESCRIPTION("PCA9641 I2C master demultiplexer driver"); > +MODULE_LICENSE("GPL v2"); >