Re: [PATCH 18/21 v5] Input: atmel_mxt_ts - cache T9 reportid range when reading object table

["Henrik Rydberg" <rydberg@euromail.se>]

Hi Daniel,

> Streamline interrupt processing by caching the T9 reportid range when
> first reading the object table.
> 
> In the process, refactor reading the object descriptor table.
> First, since the object_table entries are now exactly the same layout
> in device memory and in the driver, allocate an appropriately sized
> array and fetch the entire table directly into it in a single i2c
> transaction.  Since a 6 byte table object requires 10 bytes to read,
> doing this dramatically reduces overhead.
> 
> Note: The cached T9 reportid's are initialized to 0, which is an invalid
> reportid.  Thus, the checks in the interrupt handler will always fail for
> devices that do not support the T9 object.  Therefore, after doing a
> firmware update, the old object table is destroyed and all cached object
> values are reset to 0, before reading the new object table, in case
> the new firmware does not have the old objects.
> 
> This patch tested on an MXT224E.
> 
> Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
> ---
>  drivers/input/touchscreen/atmel_mxt_ts.c |   80 +++++++++++++++++-------------
>  1 files changed, 45 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
> index 7b042e5..4da12a9 100644
> --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> @@ -227,13 +227,10 @@ struct mxt_info {
>  struct mxt_object {
>  	u8 type;
>  	u16 start_address;
> -	u8 size;
> -	u8 instances;
> +	u8 size;		/* Size of each instance - 1 */
> +	u8 instances;		/* Number of instances - 1 */
>  	u8 num_report_ids;
> -
> -	/* to map object and message */
> -	u8 max_reportid;
> -};
> +} __packed;
>  
>  struct mxt_message {
>  	u8 reportid;
> @@ -251,6 +248,10 @@ struct mxt_data {
>  	unsigned int irq;
>  	unsigned int max_x;
>  	unsigned int max_y;
> +
> +	/* Cached parameters from object table */
> +	u8 T9_reportid_min;
> +	u8 T9_reportid_max;
>  };
>  
>  static bool mxt_object_readable(unsigned int type)
> @@ -458,13 +459,6 @@ static int mxt_write_reg(struct i2c_client *client, u16 reg, u8 val)
>  	return __mxt_write_reg(client, reg, 1, &val);
>  }
>  
> -static int mxt_read_object_table(struct i2c_client *client,
> -				      u16 reg, u8 *object_buf)
> -{
> -	return __mxt_read_reg(client, reg, MXT_OBJECT_SIZE,
> -				   object_buf);
> -}
> -
>  static struct mxt_object *
>  mxt_get_object(struct mxt_data *data, u8 type)
>  {
> @@ -563,7 +557,6 @@ static irqreturn_t mxt_interrupt(int irq, void *dev_id)
>  {
>  	struct mxt_data *data = dev_id;
>  	struct mxt_message message;
> -	struct mxt_object *object;
>  	struct device *dev = &data->client->dev;
>  	int id;
>  	u8 reportid;
> @@ -578,13 +571,8 @@ static irqreturn_t mxt_interrupt(int irq, void *dev_id)
>  
>  		reportid = message.reportid;
>  
> -		/* whether reportid is thing of MXT_TOUCH_MULTI_T9 */
> -		object = mxt_get_object(data, MXT_TOUCH_MULTI_T9);
> -		if (!object)
> -			goto end;
> -
> -		max_reportid = object->max_reportid;
> -		min_reportid = max_reportid - object->num_report_ids + 1;
> +		max_reportid = data->T9_reportid_max;
> +		min_reportid = data->T9_reportid_min;
>  		id = reportid - min_reportid;
>  
>  		if (reportid >= min_reportid && reportid <= max_reportid)
> @@ -719,30 +707,49 @@ static int mxt_get_info(struct mxt_data *data)
>  
>  static int mxt_get_object_table(struct mxt_data *data)
>  {
> +	struct i2c_client *client = data->client;
> +	size_t table_size;
>  	int error;
>  	int i;
> -	u16 reg;
> -	u8 reportid = 0;
> -	u8 buf[MXT_OBJECT_SIZE];
> +	u8 reportid;
>  
> +	table_size = data->info.object_num * sizeof(struct mxt_object);
> +	error = __mxt_read_reg(client, MXT_OBJECT_START, table_size,
> +			data->object_table);
> +	if (error) {
> +		kfree(data->object_table);
> +		data->object_table = NULL;
> +		return error;

Freeing the object table here does not look right. Either free it in
mxt_initialize() or move the allocation into this function as well.

> +	}
> +
> +	/* Valid Report IDs start counting from 1 */
> +	reportid = 1;
>  	for (i = 0; i < data->info.object_num; i++) {
>  		struct mxt_object *object = data->object_table + i;
> +		u8 min_id, max_id;
>  
> -		reg = MXT_OBJECT_START + MXT_OBJECT_SIZE * i;
> -		error = mxt_read_object_table(data->client, reg, buf);
> -		if (error)
> -			return error;
> -
> -		object->type = buf[0];
> -		object->start_address = (buf[2] << 8) | buf[1];
> -		object->size = buf[3];
> -		object->instances = buf[4];
> -		object->num_report_ids = buf[5];
> +		le16_to_cpus(&object->start_address);
>  
>  		if (object->num_report_ids) {
> +			min_id = reportid;
>  			reportid += object->num_report_ids *
>  					(object->instances + 1);
> -			object->max_reportid = reportid;
> +			max_id = reportid - 1;
> +		} else {
> +			min_id = 0;
> +			max_id = 0;
> +		}
> +
> +		dev_info(&data->client->dev,
> +			 "Type %2d Start %3d Size %3d Instances %2d ReportIDs %3u : %3u\n",
> +			 object->type, object->start_address, object->size + 1,
> +			 object->instances + 1, min_id, max_id);

On a normal boot, how many lines of output does this driver generate?

> +
> +		switch (object->type) {
> +		case MXT_TOUCH_MULTI_T9:
> +			data->T9_reportid_min = min_id;
> +			data->T9_reportid_max = max_id;
> +			break;
>  		}
>  	}
>  
> @@ -995,8 +1002,11 @@ static ssize_t mxt_update_fw_store(struct device *dev,
>  		/* Wait for reset */
>  		msleep(MXT_FWRESET_TIME);
>  
> +		/* Destroy old object table and any cached fields */
>  		kfree(data->object_table);
>  		data->object_table = NULL;
> +		data->T9_reportid_min = 0;
> +		data->T9_reportid_max = 0;
>  
>  		mxt_initialize(data);
>  	}
> -- 
> 1.7.7.3
> 

Thanks,
Henrik