Re: [RFC PATCH] soundwire: bus: Add flag to mark DPN_BlockCtrl1 as readonly

On 3/9/20 12:37 PM, Srinivas Kandagatla wrote:

According to SoundWire Specification Version 1.2. "A Data Port number X (in the range 0-14) which supports only one value of WordLength may implement the WordLength field in the DPX_BlockCtrl1 Register as Read-Only, returning the fixed value of WordLength in response to reads."

Interesting.

I think it's a spec issue that you want to bring to the MIPI Audio WG attention.

The note below says 'the DPx_BlockCtrl1 Register remains as Read-Write, but the value written to the Read-Only field is not used'

Ignoring a value and returning an error are two different behaviors indeed.

My recommendation would be to add a DisCo property stating the WordLength value can be used by the bus code but not written to the Slave device registers.

As WSA881x interfaces in PDM mode making the only field "WordLength" in DPX_BlockCtrl1" fixed and read-only. Behaviour of writing to this register on WSA881x soundwire slave with Qualcomm Soundwire Controller is throwing up an error. Not sure how other controllers deal with writing to readonly registers, but this patch provides a way to avoid writes to DPN_BlockCtrl1 register by providing a ro_blockctrl1_reg flag in struct sdw_port_runtime.

Signed-off-by: Srinivas Kandagatla srinivas.kandagatla@linaro.org

I will send patch for WSA881x to include this change once this patch is accepted.

drivers/soundwire/bus.h | 2 ++ drivers/soundwire/stream.c | 17 ++++++++++------- 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h index 204204a26db8..791e8d14093e 100644 --- a/drivers/soundwire/bus.h +++ b/drivers/soundwire/bus.h @@ -79,6 +79,7 @@ int sdw_find_col_index(int col);

• @num: Port number. For audio streams, valid port number ranges from
• [1,14]
• @ch_mask: Channel mask

• • @ro_blockctrl1_reg: Read Only flag for DPN_BlockCtrl1 register
  • @transport_params: Transport parameters
  • @port_params: Port parameters
  • @port_node: List node for Master or Slave port_list

@@ -89,6 +90,7 @@ int sdw_find_col_index(int col); struct sdw_port_runtime { int num; int ch_mask;

• bool ro_blockctrl1_reg; struct sdw_transport_params transport_params; struct sdw_port_params port_params; struct list_head port_node;

diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c index 00348d1fc606..4491643aeb4a 100644 --- a/drivers/soundwire/stream.c +++ b/drivers/soundwire/stream.c @@ -167,13 +167,15 @@ static int sdw_program_slave_port_params(struct sdw_bus *bus, return ret; }

• /* Program DPN_BlockCtrl1 register */
• ret = sdw_write(s_rt->slave, addr2, (p_params->bps - 1));
• if (ret < 0) {

• dev_err(&s_rt->slave->dev,
  

• 	"DPN_BlockCtrl1 register write failed for port %d\n",
  

• 	t_params->port_num);
  

• return ret;
  

• if (!p_rt->ro_blockctrl1_reg) {

• /* Program DPN_BlockCtrl1 register */
  

• ret = sdw_write(s_rt->slave, addr2, (p_params->bps - 1));
  

• if (ret < 0) {
  

• 	dev_err(&s_rt->slave->dev,
  

• 		"DPN_BlockCtrl1 register write failed for port %d\n",
  

• 		t_params->port_num);
  

• 	return ret;
  

• }
  

  }

  /* Program DPN_SampleCtrl1 register */

@@ -1195,6 +1197,7 @@ static struct sdw_port_runtime

p_rt->ch_mask = port_config[port_index].ch_mask; p_rt->num = port_config[port_index].num;

• p_rt->ro_blockctrl1_reg = port_config[port_index].ro_blockctrl1_reg;

  return p_rt; }