Re: [PATCH 5/6] soundwire: qcom: update register read/write routine

On 1/29/21 11:32 AM, Srinivas Kandagatla wrote:

In the existing code every soundwire register read and register write are kinda blocked. Each of these are using a special command id that

what does 'kinda blocked' mean?

generates interrupt after it successfully finishes. This is really overhead, limiting and not really necessary unless we are doing something special.

We can simply read/write the fifo that should also give exactly what we need! This will also allow to read/write registers in interrupt context, which was not possible with the special command approach.

This is really unclear, sorry.

• if (id != SWR_BROADCAST_CMD_ID) {

• if (id < 14)
  

• 	id += 1;
  

• else
  

• 	id = 0;
  

that is really odd. if id=13 (group2) then id becomes 14 (master address). A comment is really needed here.

• if (cmd_id == SWR_BROADCAST_CMD_ID) {

• /*
  

•  * sleep for 10ms for MSM soundwire variant to allow broadcast
  

•  * command to complete.
  

that's also super-odd. There is nothing in SoundWire that makes any difference between a regular and a broadcast command. they all complete in the same time (a frame).

•  */
  

• ret = wait_for_completion_timeout(&swrm->broadcast, (2 * HZ/10));
  

is this 10ms really or dependent on CONFIG_HZ?

• if (!ret)
  

• 	ret = SDW_CMD_IGNORED;
  

• else
  

• 	ret = SDW_CMD_OK;
  

no CMD_FAILED support?

+static int qcom_swrm_cmd_fifo_rd_cmd(struct qcom_swrm_ctrl *swrm,

• 		     u8 dev_addr, u16 reg_addr,
  

• 		     u32 len, u8 *rval)
  

+{

• u32 val;
• u32 retry_attempt = 0;
• u32 cmd_data;
• int ret = SDW_CMD_OK;
• mutex_lock(&swrm->io_lock);
• val = swrm_get_packed_reg_val(&swrm->rcmd_id, len, dev_addr, reg_addr);
• /* wait for FIFO RD to complete to avoid overflow */
• usleep_range(100, 105);
• swrm->reg_write(swrm, SWRM_CMD_FIFO_RD_CMD, val);
• /* wait for FIFO RD CMD complete to avoid overflow */
• usleep_range(250, 255);

+retry_read:

• swrm->reg_read(swrm, SWRM_CMD_FIFO_RD_FIFO_ADDR, &cmd_data);
• rval[0] = cmd_data & 0xFF;
• if ((((cmd_data) & 0xF00) >> 8) != swrm->rcmd_id) {

• if (retry_attempt < MAX_FIFO_RD_FAIL_RETRY) {
  

• 	/* wait 500 us before retry on fifo read failure */
  

• 	usleep_range(500, 505);
  

• 	if (retry_attempt == (MAX_FIFO_RD_FAIL_RETRY - 1)) {
  

• 		swrm->reg_write(swrm, SWRM_CMD_FIFO_CMD, 0x1);
  

• 		swrm->reg_write(swrm, SWRM_CMD_FIFO_RD_CMD, val);
  

• 	}
  

• 	retry_attempt++;
  

• 	goto retry_read;
  

• } else {
  

• 	dev_err(swrm->dev,
  

• 			"failed to read fifo: reg: 0x%x, \
  

• 			rcmd_id: 0x%x, dev_num: 0x%x, cmd_data: 0x%x\n",
  

• 			reg_addr, swrm->rcmd_id,
  

• 			dev_addr, cmd_data);
  

• 	ret = SDW_CMD_IGNORED;
  

• }
  

  }

the flow seems complicated with multiple tests and goto? Can this be simplified?