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[94.114.232.236]) by smtp.gmail.com with ESMTPSA id hv13-20020a17090760cd00b00741a0c3f4cdsm782281ejc.189.2022.10.07.00.55.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Oct 2022 00:55:21 -0700 (PDT) From: Patrick Rudolph To: Peter Rosin Cc: robh@kernel.org, laurent.pinchart@ideasonboard.com, wsa@kernel.org, Patrick Rudolph , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [v9 3/4] i2c: muxes: pca954x: Configure MAX7357 in enhanced mode Date: Fri, 7 Oct 2022 09:53:52 +0200 Message-Id: <20221007075354.568752-4-patrick.rudolph@9elements.com> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20221007075354.568752-1-patrick.rudolph@9elements.com> References: <20221007075354.568752-1-patrick.rudolph@9elements.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org The MAX7357 and MAX7358 have 6 additional registers called enhanced mode in the following paragraphs. While the MAX7357 exposes those registers without a special sequence, the MAX7358 requires an unlock sequence. The enhanced mode allows to configure optional features which are nice to have on an I2C mux, but are not mandatory for it's general operation. As I don't have a MAX7358 for testing the special unlock sequence the enhanced mode isn't used on the MAX7358, but it could be added later if required. The MAX7357 enhanced mode is used to configure the chip to - Disable interrupts on bus locked up detection - Enable bus locked-up clearing - Disconnect only locked bus instead of all channels This configuration protects the I2C tree from total failure and attempts to unbrick the faulty bus. It's unclear why this isn't the default configuration. Tested using the MAX7357 and verified that the stalled bus is disconnected while the other channels remain operational. Signed-off-by: Patrick Rudolph --- drivers/i2c/muxes/i2c-mux-pca954x.c | 46 ++++++++++++++++++++++++++++- 1 file changed, 45 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c index 4b63b1eb669e..992976fa6798 100644 --- a/drivers/i2c/muxes/i2c-mux-pca954x.c +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c @@ -57,6 +57,37 @@ #define PCA954X_IRQ_OFFSET 4 +/* + * The MAX7357 and MAX7358 have 6 additional registers called enhanced mode + * in the following paragraphs. While the MAX7357 exposes those registers + * without a special sequence, the MAX7358 requires an unlock sequence. + * + * The first enhanced mode register called CONF allows to configure + * additional features. + */ +#define MAX7357_REG_SWITCH 0 +#define MAX7357_REG_CONF 1 +#define MAX7357_CONF_INT_ENABLE BIT(0) +#define MAX7357_CONF_FLUSH_OUT BIT(1) +#define MAX7357_CONF_RELEASE_INT BIT(2) +#define MAX7357_CONF_LOCK_UP_CLEAR_ON_READ BIT(3) +#define MAX7357_CONF_DISCON_SINGLE_CHAN BIT(4) +#define MAX7357_CONF_BUS_LOCKUP_DETECTION_DISABLE BIT(5) +#define MAX7357_CONF_ENABLE_BASIC_MODE BIT(6) +#define MAX7357_CONF_PRECONNECT_TEST BIT(7) + +/* + * On boot the MAX735x behave like a regular MUX. Apply a fixed + * default configuration on MAX7357 that: + * - disables interrupts + * - sents automatically flush-out sequence on locked-up channels + when a lock-up condition is detected + * - isolates only the locked channel instead of all channels + * - doesn't disable bus lock-up detection. + */ +#define MAX7357_CONF_DEFAULTS (MAX7357_CONF_FLUSH_OUT | \ + MAX7357_CONF_DISCON_SINGLE_CHAN) + enum pca_type { max_7367, max_7368, @@ -82,6 +113,7 @@ struct chip_desc { u8 nchans; u8 enable; /* used for muxes only */ u8 has_irq; + u8 maxim_enhanced_mode; enum muxtype { pca954x_ismux = 0, pca954x_isswi @@ -113,6 +145,7 @@ static const struct chip_desc chips[] = { [max_7357] = { .nchans = 8, .muxtype = pca954x_isswi, + .maxim_enhanced_mode = 1, .id = { .manufacturer_id = I2C_DEVICE_ID_NONE }, }, [max_7358] = { @@ -452,6 +485,7 @@ static void pca954x_cleanup(struct i2c_mux_core *muxc) static int pca954x_init(struct i2c_client *client, struct pca954x *data) { + struct i2c_adapter *adap = client->adapter; int ret; if (data->idle_state >= 0) @@ -459,7 +493,17 @@ static int pca954x_init(struct i2c_client *client, struct pca954x *data) else data->last_chan = 0; /* Disconnect multiplexer */ - ret = i2c_smbus_write_byte(client, data->last_chan); + if (data->chip->maxim_enhanced_mode) { + if (i2c_check_functionality(adap, I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) { + ret = i2c_smbus_write_byte_data(client, data->last_chan, + MAX7357_CONF_DEFAULTS); + } else { + dev_warn(&client->dev, "Didn't configure enhanced defaults\n"); + ret = i2c_smbus_write_byte(client, data->last_chan); + } + } else { + ret = i2c_smbus_write_byte(client, data->last_chan); + } if (ret < 0) data->last_chan = 0;