Re: [Intel-gfx] [PATCH] drm/i915/dsi: Parse the I2C element from the VBT MIPI sequence block

[Hans de Goede <hdegoede@redhat.com>]

Hi Vivek,

On 03-01-2020 01:00, Vivek Kasireddy wrote:
> Parsing the i2c element is mainly done to transfer the payload from the
> MIPI sequence block to the relevant slave device. In some cases, the
> commands that are part of the payload can be used to turn on the backlight.
> 
> This patch is actually a refactored version of this old patch:
> https://lists.freedesktop.org/archives/intel-gfx/2014-December/056897.html
> 
> In addition to the refactoring, the old patch is augmented by looking up
> the i2c bus from ACPI NS instead of relying on the bus number provided
> in the VBT.
> 
> Cc: Deepak M <m.deepak@intel.com>
> Cc: Nabendu Maiti <nabendu.bikash.maiti@intel.com>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> Cc: Bob Paauwe <bob.j.paauwe@intel.com>
> Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>

Thank you for this patch, I have been doing a lot of work to make
DSI panels on Bay Trail and Cherry Trail devices work better, as such
I've done a lot of testing of DSI panels. But I have never seen any
MIPI sequences actually use the i2c commands. May I ask how you have
tested this? Do you have a device which actually uses the i2c commands?

I also have some small review comments inline:

> ---
>   drivers/gpu/drm/i915/display/intel_dsi.h     |  3 +
>   drivers/gpu/drm/i915/display/intel_dsi_vbt.c | 93 ++++++++++++++++++++
>   2 files changed, 96 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dsi.h b/drivers/gpu/drm/i915/display/intel_dsi.h
> index b15be5814599..5651bc8aa5c2 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsi.h
> +++ b/drivers/gpu/drm/i915/display/intel_dsi.h
> @@ -68,6 +68,9 @@ struct intel_dsi {
>   	/* number of DSI lanes */
>   	unsigned int lane_count;
>   
> +	/* i2c bus associated with the slave device */
> +	int i2c_bus_num;
> +
>   	/*
>   	 * video mode pixel format
>   	 *
> diff --git a/drivers/gpu/drm/i915/display/intel_dsi_vbt.c b/drivers/gpu/drm/i915/display/intel_dsi_vbt.c
> index f90946c912ee..60441a5a3dba 100644
> --- a/drivers/gpu/drm/i915/display/intel_dsi_vbt.c
> +++ b/drivers/gpu/drm/i915/display/intel_dsi_vbt.c
> @@ -83,6 +83,12 @@ static struct gpio_map vlv_gpio_table[] = {
>   	{ VLV_GPIO_NC_11_PANEL1_BKLTCTL },
>   };
>   
> +struct i2c_adapter_lookup {
> +	u16 slave_addr;
> +	struct intel_dsi *intel_dsi;
> +	acpi_handle dev_handle;
> +};
> +
>   #define CHV_GPIO_IDX_START_N		0
>   #define CHV_GPIO_IDX_START_E		73
>   #define CHV_GPIO_IDX_START_SW		100
> @@ -375,8 +381,93 @@ static const u8 *mipi_exec_gpio(struct intel_dsi *intel_dsi, const u8 *data)
>   	return data;
>   }
>   
> +static int i2c_adapter_lookup(struct acpi_resource *ares, void *data)
> +{
> +	struct i2c_adapter_lookup *lookup = data;
> +	struct intel_dsi *intel_dsi = lookup->intel_dsi;
> +	struct acpi_resource_i2c_serialbus *sb;
> +	struct i2c_adapter *adapter;
> +	acpi_handle adapter_handle;
> +	acpi_status status;
> +
> +	if (intel_dsi->i2c_bus_num >= 0 ||
> +	    !i2c_acpi_get_i2c_resource(ares, &sb))
> +		return 1;
> +
> +	if (lookup->slave_addr != sb->slave_address)
> +		return 1;
> +
> +	status = acpi_get_handle(lookup->dev_handle,
> +				 sb->resource_source.string_ptr,
> +				 &adapter_handle);
> +	if (ACPI_FAILURE(status))
> +		return 1;
> +
> +	adapter = i2c_acpi_find_adapter_by_handle(adapter_handle);
> +	if (adapter)
> +		intel_dsi->i2c_bus_num = adapter->nr;
> +
> +	return 1;
> +}
> +
>   static const u8 *mipi_exec_i2c(struct intel_dsi *intel_dsi, const u8 *data)
>   {
> +	struct drm_device *dev = intel_dsi->base.base.dev;
> +	struct i2c_adapter *adapter;
> +	struct acpi_device *acpi_dev;
> +	struct list_head resource_list;
> +	struct i2c_adapter_lookup lookup;
> +	struct i2c_msg msg;
> +	int ret;
> +	u8 vbt_i2c_bus_num = *(data + 2);
> +	u16 slave_addr = *(u16 *)(data + 3);
> +	u8 reg_offset = *(data + 5);
> +	u8 payload_size = *(data + 6);
> +	u8 *payload_data;
> +
> +	if (intel_dsi->i2c_bus_num < 0) {
> +		intel_dsi->i2c_bus_num = vbt_i2c_bus_num;
> +
> +		acpi_dev = ACPI_COMPANION(&dev->pdev->dev);
> +		if (acpi_dev) {
> +			memset(&lookup, 0, sizeof(lookup));
> +			lookup.slave_addr = slave_addr;
> +			lookup.intel_dsi = intel_dsi;
> +			lookup.dev_handle = acpi_device_handle(acpi_dev);
> +
> +			INIT_LIST_HEAD(&resource_list);
> +			acpi_dev_get_resources(acpi_dev, &resource_list,
> +					       i2c_adapter_lookup,
> +					       &lookup);
> +			acpi_dev_free_resource_list(&resource_list);
> +		}
> +	}
> +
> +	adapter = i2c_get_adapter(intel_dsi->i2c_bus_num);
> +	if (!adapter)
> +		goto out;

This should never happen, so you should put a DRM_DEV_WARN here.

> +
> +	payload_data = kzalloc(payload_size + 1, GFP_KERNEL);
> +	if (!payload_data)
> +		goto out;
> +
> +	payload_data[0] = reg_offset;
> +	memcpy(&payload_data[1], (data + 7), payload_size);
> +
> +	msg.addr = slave_addr;
> +	msg.flags = 0;
> +	msg.len = payload_size + 1;
> +	msg.buf = payload_data;
> +
> +	ret = i2c_transfer(adapter, &msg, 1);
> +	if (ret < 0)
> +		DRM_ERROR("i2c transfer failed");

DRM_DEV_ERROR? And maybe some more info, like the register which
the transfer is going to + payload size?

> +
> +	kfree(payload_data);
> +	i2c_put_adapter(adapter);
> +

Just put out here, no need for the DRM_DEBUG (which should no
longer be a debug now that we implement this) below, since we
WARN or ERROR on all goto out; statements above.

out:

> +	return data + payload_size + 7;

And drop these 3 lines:

> +out:
>   	DRM_DEBUG_KMS("Skipping I2C element execution\n");
>   
>   	return data + *(data + 6) + 7;



> @@ -664,6 +755,8 @@ bool intel_dsi_vbt_init(struct intel_dsi *intel_dsi, u16 panel_id)
>   	intel_dsi->panel_off_delay = pps->panel_off_delay / 10;
>   	intel_dsi->panel_pwr_cycle_delay = pps->panel_power_cycle_delay / 10;
>   
> +	intel_dsi->i2c_bus_num = -1;
> +
>   	/* a regular driver would get the device in probe */
>   	for_each_dsi_port(port, intel_dsi->ports) {
>   		mipi_dsi_attach(intel_dsi->dsi_hosts[port]->device);
> 

Regards,

Hans

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