linux-kernel - Re: [alsa-devel] [RFC PATCH 21/40] soundwire: export helpers to find row and column values

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Message-ID: <75539c39-da33-efba-d320-42fab738c5f0@linux.intel.com>
Date:   Mon, 5 Aug 2019 10:27:16 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Sanyog Kale <sanyog.r.kale@...el.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        tiwai@...e.de, broonie@...nel.org, vkoul@...nel.org,
        gregkh@...uxfoundation.org, jank@...ence.com,
        srinivas.kandagatla@...aro.org, slawomir.blauciak@...el.com
Subject: Re: [alsa-devel] [RFC PATCH 21/40] soundwire: export helpers to find
 row and column values



On 8/5/19 4:39 AM, Sanyog Kale wrote:
> On Thu, Jul 25, 2019 at 06:40:13PM -0500, Pierre-Louis Bossart wrote:
>> Add a prefix for common tables and export 2 helpers to set the frame
>> shapes based on row/col values.
>>
>> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
>> ---
>>   drivers/soundwire/bus.h    |  7 +++++--
>>   drivers/soundwire/stream.c | 14 ++++++++------
>>   2 files changed, 13 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h
>> index 06ac4adb0074..c57c9c23f6ca 100644
>> --- a/drivers/soundwire/bus.h
>> +++ b/drivers/soundwire/bus.h
>> @@ -73,8 +73,11 @@ struct sdw_msg {
>>   
>>   #define SDW_DOUBLE_RATE_FACTOR		2
>>   
>> -extern int rows[SDW_FRAME_ROWS];
>> -extern int cols[SDW_FRAME_COLS];
>> +extern int sdw_rows[SDW_FRAME_ROWS];
>> +extern int sdw_cols[SDW_FRAME_COLS];
>> +
>> +int sdw_find_row_index(int row);
>> +int sdw_find_col_index(int col);
> 
> We use index values only in bank switch operations to program registers. Do we
> really need to export sdw_find_row_index & sdw_find_col_index?? If i understand
> correctly the allocation algorithm only needs to know about cols and rows values
> and not index.

The allocation does work with cols and rows indeed, but will first run 
the code below where the information f is required:

static int sdw_select_row_col(struct sdw_bus *bus, int clk_freq)
{
	struct sdw_master_prop *prop = &bus->prop;
	int frame_int, frame_freq;
	int r, c;

	for (c = 0; c < SDW_FRAME_COLS; c++) {
		for (r = 0; r < SDW_FRAME_ROWS; r++) {
			if (sdw_rows[r] != prop->default_row ||
			    sdw_cols[c] != prop->default_col)
				continue;

			frame_int = sdw_rows[r] * sdw_cols[c];
			frame_freq = clk_freq / frame_int;

			if ((clk_freq - (frame_freq * SDW_FRAME_CTRL_BITS)) <
			    bus->params.bandwidth)
				continue;

			bus->params.row = sdw_rows[r];
			bus->params.col = sdw_cols[c];
			return 0;
		}
	}

	return -EINVAL;
}

as for the two helpers, they are used in both the allocation and the 
cadence code (to determine the initial frame shape from properties).

And other solutions for non-Intel platforms will also need this to 
convert from indices to frame shape.

So yes all of this is needed.


> 
>>   
>>   /**
>>    * sdw_port_runtime: Runtime port parameters for Master or Slave
>> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
>> index a0476755a459..53f5e790fcd7 100644
>> --- a/drivers/soundwire/stream.c
>> +++ b/drivers/soundwire/stream.c
>> @@ -21,37 +21,39 @@
>>    * The rows are arranged as per the array index value programmed
>>    * in register. The index 15 has dummy value 0 in order to fill hole.
>>    */
>> -int rows[SDW_FRAME_ROWS] = {48, 50, 60, 64, 75, 80, 125, 147,
>> +int sdw_rows[SDW_FRAME_ROWS] = {48, 50, 60, 64, 75, 80, 125, 147,
>>   			96, 100, 120, 128, 150, 160, 250, 0,
>>   			192, 200, 240, 256, 72, 144, 90, 180};
>>   
>> -int cols[SDW_FRAME_COLS] = {2, 4, 6, 8, 10, 12, 14, 16};
>> +int sdw_cols[SDW_FRAME_COLS] = {2, 4, 6, 8, 10, 12, 14, 16};
>>   
>> -static int sdw_find_col_index(int col)
>> +int sdw_find_col_index(int col)
>>   {
>>   	int i;
>>   
>>   	for (i = 0; i < SDW_FRAME_COLS; i++) {
>> -		if (cols[i] == col)
>> +		if (sdw_cols[i] == col)
>>   			return i;
>>   	}
>>   
>>   	pr_warn("Requested column not found, selecting lowest column no: 2\n");
>>   	return 0;
>>   }
>> +EXPORT_SYMBOL(sdw_find_col_index);
>>   
>> -static int sdw_find_row_index(int row)
>> +int sdw_find_row_index(int row)
>>   {
>>   	int i;
>>   
>>   	for (i = 0; i < SDW_FRAME_ROWS; i++) {
>> -		if (rows[i] == row)
>> +		if (sdw_rows[i] == row)
>>   			return i;
>>   	}
>>   
>>   	pr_warn("Requested row not found, selecting lowest row no: 48\n");
>>   	return 0;
>>   }
>> +EXPORT_SYMBOL(sdw_find_row_index);
>>   
>>   static int _sdw_program_slave_port_params(struct sdw_bus *bus,
>>   					  struct sdw_slave *slave,
>> -- 
>> 2.20.1
>>
>