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Ruhl" , linux-kernel@vger.kernel.org, intel-xe@lists.freedesktop.org, stable@vger.kernel.org Subject: [PATCH v6 3/3] drm/xe/i2c: Keep the i2c controller always enabled Date: Wed, 22 Jul 2026 15:35:54 +0200 Message-ID: <20260722133554.2079612-4-heikki.krogerus@linux.intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260722133554.2079612-1-heikki.krogerus@linux.intel.com> References: <20260722133554.2079612-1-heikki.krogerus@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Some platforms make an assumption that the i2c controller's enabled state indicates also the power state of the controller. This can create a problem when the controller is in disabled state, because the hardware may assume incorrectly that it is then also in low-power state. To fix this, the controller is kept enabled by taking over the IC_ENABLE register. The controller has to be disabled when the configuration is updated and when the target address or the slave address are assigned, so disabling it when IC_CON, IC_TAR or IC_SAR registers are programmed, and then re-enabling it again. Fixes: f0e53aadd702 ("drm/xe: Support for I2C attached MCUs") Cc: stable@vger.kernel.org Signed-off-by: Heikki Krogerus --- drivers/gpu/drm/xe/xe_i2c.c | 49 ++++++++++++++++++++++++++++++++++++- drivers/gpu/drm/xe/xe_i2c.h | 1 + 2 files changed, 49 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/xe/xe_i2c.c b/drivers/gpu/drm/xe/xe_i2c.c index f1bd4ddad26f5..a7737422baefc 100644 --- a/drivers/gpu/drm/xe/xe_i2c.c +++ b/drivers/gpu/drm/xe/xe_i2c.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include #include @@ -212,11 +213,40 @@ void xe_i2c_irq_postinstall(struct xe_device *xe) xe_mmio_rmw32(mmio, I2C_CONFIG_CMD, PCI_COMMAND_INTX_DISABLE, 0); } +/* See "Disabling DW_apb_i2c" in the DesignWare DW_abp_i2c databook. */ +static void xe_i2c_disable(struct xe_i2c *i2c) +{ + int timeout = 100; + u32 status; + + xe_mmio_rmw32(i2c->mmio, I2C_REG(DW_IC_ENABLE), DW_IC_ENABLE_ENABLE, 0); + + do { + status = xe_mmio_read32(i2c->mmio, I2C_REG(DW_IC_ENABLE_STATUS)); + if (!(status & DW_IC_ENABLE_ENABLE)) + return; + /* Can't sleep here. */ + udelay(25); + } while (timeout--); + + dev_warn(i2c->drm_dev, "timeout in disabling i2c adapter\n"); +} + static int xe_i2c_read(void *context, unsigned int reg, unsigned int *val) { struct xe_i2c *i2c = context; - *val = xe_mmio_read32(i2c->mmio, XE_REG(reg + I2C_MEM_SPACE_OFFSET)); + *val = xe_mmio_read32(i2c->mmio, I2C_REG(reg)); + + switch (reg) { + case DW_IC_ENABLE: + case DW_IC_ENABLE_STATUS: + FIELD_MODIFY(DW_IC_ENABLE_ENABLE, val, + i2c->ic_enable & DW_IC_ENABLE_ENABLE); + break; + default: + break; + } return 0; } @@ -226,6 +256,23 @@ static int xe_i2c_write(void *context, unsigned int reg, unsigned int val) struct xe_i2c *i2c = context; switch (reg) { + case DW_IC_CON: + case DW_IC_TAR: + case DW_IC_SAR: + /* Disable the controller. */ + xe_i2c_disable(i2c); + + /* Write the register. */ + xe_mmio_write32(i2c->mmio, I2C_REG(reg), val); + + /* Enable the controller. */ + xe_mmio_rmw32(i2c->mmio, I2C_REG(DW_IC_ENABLE), 0, DW_IC_ENABLE_ENABLE); + return 0; + case DW_IC_ENABLE: + i2c->ic_enable = val; + /* Other fields can be updated except the enable bit. */ + val |= DW_IC_ENABLE_ENABLE; + break; case DW_IC_SMBUS_INTR_MASK: /* Make sure the Alert is never masked. */ val |= DW_IC_SMBUS_INTR_ALERT; diff --git a/drivers/gpu/drm/xe/xe_i2c.h b/drivers/gpu/drm/xe/xe_i2c.h index b200966b00484..d63adacfefe71 100644 --- a/drivers/gpu/drm/xe/xe_i2c.h +++ b/drivers/gpu/drm/xe/xe_i2c.h @@ -37,6 +37,7 @@ struct xe_i2c { struct platform_device *pdev; struct i2c_adapter *adapter; struct i2c_client *client[XE_I2C_MAX_CLIENTS]; + unsigned int ic_enable; struct notifier_block bus_notifier; struct work_struct work; -- 2.50.1