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. Signed-off-by: Heikki Krogerus <[email protected]> --- drivers/gpu/drm/xe/xe_i2c.c | 55 +++++++++++++++++++++++++++++++++++-- drivers/gpu/drm/xe/xe_i2c.h | 1 + 2 files changed, 54 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/xe/xe_i2c.c b/drivers/gpu/drm/xe/xe_i2c.c index 0495b561957a2..e2d8e77653cf2 100644 --- a/drivers/gpu/drm/xe/xe_i2c.c +++ b/drivers/gpu/drm/xe/xe_i2c.c @@ -8,6 +8,7 @@ #include <drm/drm_print.h> #include <linux/array_size.h> #include <linux/container_of.h> +#include <linux/delay.h> #include <linux/device.h> #include <linux/designware_i2c.h> #include <linux/err.h> @@ -294,11 +295,40 @@ static void xe_i2c_remove_irq(struct xe_i2c *i2c) irq_domain_remove(i2c->irqdomain); } +/* 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), 1, 0); + + do { + status = xe_mmio_read32(i2c->mmio, I2C_REG(DW_IC_ENABLE_STATUS)); + if (!(status & 1)) + return; + /* Can't sleep here. */ + udelay(25); + } while (timeout--); + + dev_warn(&i2c->adapter->dev, "timeout in disabling 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; } @@ -307,7 +337,28 @@ static int xe_i2c_write(void *context, unsigned int reg, unsigned int val) { struct xe_i2c *i2c = context; - xe_mmio_write32(i2c->mmio, XE_REG(reg + I2C_MEM_SPACE_OFFSET), val); + 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, 1); + break; + case DW_IC_ENABLE: + i2c->ic_enable = val; + /* Other fields can be updated except the enable bit. */ + val |= DW_IC_ENABLE_ENABLE; + fallthrough; + default: + xe_mmio_write32(i2c->mmio, I2C_REG(reg), val); + break; + } return 0; } diff --git a/drivers/gpu/drm/xe/xe_i2c.h b/drivers/gpu/drm/xe/xe_i2c.h index b3327db998708..231e36df09017 100644 --- a/drivers/gpu/drm/xe/xe_i2c.h +++ b/drivers/gpu/drm/xe/xe_i2c.h @@ -39,6 +39,7 @@ 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
