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Thu, 26 May 2022 20:53:35 +0000 (GMT) Received: from v0005c16.aus.stglabs.ibm.com (unknown [9.211.46.254]) by b03ledav003.gho.boulder.ibm.com (Postfix) with ESMTP; Thu, 26 May 2022 20:53:35 +0000 (GMT) From: Eddie James To: linux-i2c@vger.kernel.org Cc: linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, wsa@kernel.org, peda@axentia.se, jic23@kernel.org, lars@metafoo.de, eajames@linux.ibm.com, miltonm@us.ibm.com, joel@jms.id.au Subject: [PATCH 1/2] i2c: core: Add mux root adapter operations Date: Thu, 26 May 2022 15:53:33 -0500 Message-Id: <20220526205334.64114-2-eajames@linux.ibm.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20220526205334.64114-1-eajames@linux.ibm.com> References: <20220526205334.64114-1-eajames@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: Sz_QaotiDhXEVzWw2UM8W9OEnTnaS82F X-Proofpoint-GUID: Sz_QaotiDhXEVzWw2UM8W9OEnTnaS82F X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.874,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-05-26_10,2022-05-25_02,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 malwarescore=0 bulkscore=0 spamscore=0 impostorscore=0 priorityscore=1501 adultscore=0 mlxlogscore=999 phishscore=0 clxscore=1015 suspectscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2204290000 definitions=main-2205260095 X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org Some I2C clients need the ability to control the root I2C bus even if the endpoint device is behind a mux. For example, a driver for a chip that can't handle any I2C traffic on the bus while coming out of reset (including an I2C-driven mux switching channels) may need to lock the root bus with the mux selection fixed for the entire time the device is in reset. For this purpose, add a new structure containing two function pointers to the adapter structure. These functions pointers should be defined for every adapter. The lock_select operation, for a mux adapter, locks the parent adpaters up to the root and selects the adapter's channel. The unlock_deselect operation deselects the mux channel and unlocks all the adapters. For a non-mux adapter, the operations lock and unlock the adapters up to the root. This scheme should work with multiple levels of muxes and regular adapters in between. Signed-off-by: Eddie James Reported-by: kernel test robot Reviewed-by: Joel Stanley --- drivers/i2c/i2c-core-base.c | 38 ++++++++++++++++++++++++++++ drivers/i2c/i2c-mux.c | 50 +++++++++++++++++++++++++++++++++++++ include/linux/i2c.h | 42 +++++++++++++++++++++++++++++++ 3 files changed, 130 insertions(+) diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c index d43db2c3876e..e2c365348e1f 100644 --- a/drivers/i2c/i2c-core-base.c +++ b/drivers/i2c/i2c-core-base.c @@ -1357,6 +1357,41 @@ static const struct i2c_lock_operations i2c_adapter_lock_ops = { .unlock_bus = i2c_adapter_unlock_bus, }; +/* + * For a non-mux adapter, the lock_select operation locks the chain of + * adapters upwards, returning the root. If there's a mux above this adapter + * somehow, it should also get locked and the desired channel selected. + */ +static struct i2c_adapter *i2c_adapter_lock_select(struct i2c_adapter *adapter) +{ + struct i2c_adapter *ret = adapter; + struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter); + + if (parent) { + ret = parent->mux_root_ops->lock_select(parent); + if (IS_ERR(ret)) + return ret; + } + + adapter->lock_ops->lock_bus(adapter, I2C_LOCK_ROOT_ADAPTER); + return ret; +} + +static void i2c_adapter_unlock_deselect(struct i2c_adapter *adapter) +{ + struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter); + + adapter->lock_ops->unlock_bus(adapter, I2C_LOCK_ROOT_ADAPTER); + + if (parent) + parent->mux_root_ops->unlock_deselect(parent); +} + +static const struct i2c_mux_root_operations i2c_adapter_mux_root_ops = { + .lock_select = i2c_adapter_lock_select, + .unlock_deselect = i2c_adapter_unlock_deselect, +}; + static void i2c_host_notify_irq_teardown(struct i2c_adapter *adap) { struct irq_domain *domain = adap->host_notify_domain; @@ -1452,6 +1487,9 @@ static int i2c_register_adapter(struct i2c_adapter *adap) if (!adap->lock_ops) adap->lock_ops = &i2c_adapter_lock_ops; + if (!adap->mux_root_ops) + adap->mux_root_ops = &i2c_adapter_mux_root_ops; + adap->locked_flags = 0; rt_mutex_init(&adap->bus_lock); rt_mutex_init(&adap->mux_lock); diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c index 774507b54b57..c7db770e4198 100644 --- a/drivers/i2c/i2c-mux.c +++ b/drivers/i2c/i2c-mux.c @@ -210,6 +210,49 @@ static void i2c_parent_unlock_bus(struct i2c_adapter *adapter, rt_mutex_unlock(&parent->mux_lock); } +/* + * For a mux adapter, the lock_select operation first locks just like the + * lock_bus operation. Then it selects the channel for this adapter and + * returns the root adapter. If there is another mux above this one, calling + * the parent lock_select should ensure that the channel is correctly + * selected. + */ +static struct i2c_adapter *i2c_mux_lock_select(struct i2c_adapter *adapter) +{ + int ret; + struct i2c_mux_priv *priv = adapter->algo_data; + struct i2c_mux_core *muxc = priv->muxc; + struct i2c_adapter *parent = muxc->parent; + + rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter)); + + adapter = parent->mux_root_ops->lock_select(parent); + if (IS_ERR(adapter)) + return adapter; + + ret = muxc->select(muxc, priv->chan_id); + if (ret < 0) { + parent->mux_root_ops->unlock_deselect(parent); + rt_mutex_unlock(&parent->mux_lock); + return ERR_PTR(ret); + } + + return adapter; +} + +static void i2c_mux_unlock_deselect(struct i2c_adapter *adapter) +{ + struct i2c_mux_priv *priv = adapter->algo_data; + struct i2c_mux_core *muxc = priv->muxc; + struct i2c_adapter *parent = muxc->parent; + + if (muxc->deselect) + muxc->deselect(muxc, priv->chan_id); + + parent->mux_root_ops->unlock_deselect(parent); + rt_mutex_unlock(&parent->mux_lock); +} + struct i2c_adapter *i2c_root_adapter(struct device *dev) { struct device *i2c; @@ -279,6 +322,11 @@ static const struct i2c_lock_operations i2c_parent_lock_ops = { .unlock_bus = i2c_parent_unlock_bus, }; +static const struct i2c_mux_root_operations i2c_mux_root_ops = { + .lock_select = i2c_mux_lock_select, + .unlock_deselect = i2c_mux_unlock_deselect, +}; + int i2c_mux_add_adapter(struct i2c_mux_core *muxc, u32 force_nr, u32 chan_id, unsigned int class) @@ -339,6 +387,8 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc, else priv->adap.lock_ops = &i2c_parent_lock_ops; + priv->adap.mux_root_ops = &i2c_mux_root_ops; + /* Sanity check on class */ if (i2c_mux_parent_classes(parent) & class) dev_err(&parent->dev, diff --git a/include/linux/i2c.h b/include/linux/i2c.h index fbda5ada2afc..a3596f61b417 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -583,6 +583,26 @@ struct i2c_lock_operations { void (*unlock_bus)(struct i2c_adapter *adapter, unsigned int flags); }; +/** + * struct i2c_mux_root_operations - represent operations to lock and select + * the adapter's mux channel (if a mux is present) + * @lock_select: Get exclusive access to the root I2C bus adapter with the + * correct mux channel selected for the adapter + * @unlock_deslect: Release exclusive access to the root I2C bus adapter and + * deselect the mux channel for the adapter + * + * Some I2C clients need the ability to control the root I2C bus even if the + * endpoint device is behind a mux. For example, a driver for a chip that + * can't handle any I2C traffic on the bus while coming out of reset (including + * an I2C-driven mux switching channels) may need to lock the root bus with + * the mux selection fixed for the entire time the device is in reset. + * These operations are for such a purpose. + */ +struct i2c_mux_root_operations { + struct i2c_adapter *(*lock_select)(struct i2c_adapter *adapter); + void (*unlock_deselect)(struct i2c_adapter *adapter); +}; + /** * struct i2c_timings - I2C timing information * @bus_freq_hz: the bus frequency in Hz @@ -725,6 +745,7 @@ struct i2c_adapter { /* data fields that are valid for all devices */ const struct i2c_lock_operations *lock_ops; + const struct i2c_mux_root_operations *mux_root_ops; struct rt_mutex bus_lock; struct rt_mutex mux_lock; @@ -817,6 +838,27 @@ i2c_unlock_bus(struct i2c_adapter *adapter, unsigned int flags) adapter->lock_ops->unlock_bus(adapter, flags); } +/** + * i2c_lock_select_bus - Get exclusive access to the root I2C bus with the + * target's mux channel (if a mux is present) selected. + * @adapter: Target I2C bus + * + * Return the root I2C bus if mux selection succeeds, an ERR_PTR otherwise + */ +static inline struct i2c_adapter *i2c_lock_select_bus(struct i2c_adapter *adapter) +{ + return adapter->mux_root_ops->lock_select(adapter); +} + +/** + * i2c_unlock_deslect_bus - Release exclusive access to the root I2C bus + * @adapter: Target I2C bus + */ +static inline void i2c_unlock_deselect_bus(struct i2c_adapter *adapter) +{ + adapter->mux_root_ops->unlock_deselect(adapter); +} + /** * i2c_mark_adapter_suspended - Report suspended state of the adapter to the core * @adap: Adapter to mark as suspended