From a00b799cc3af9051f24bfa6e9c5366ee3280365a Mon Sep 17 00:00:00 2001 From: Niranjan H Y Date: Mon, 15 Dec 2025 11:51:26 +0530 Subject: [PATCH] SoundWire: Allow Prepare command for Simplified_CP_SM As defined in the MIPI SoundWire specification v1-2 for Simplified Channel Prepare State Machine (Simplified_CP_SM): * Figure 141 for the Simplified_CP_SM in the specification shows the "Ready" state (NF=0, P=1) that can be reached via "Prepare0 OR Prepare1" transitions. * Table 115 (Stimulus to the Channel Prepare State Machine) indicates that Prepare0 and Prepare1 are read-only/"write-ignored" bits for Simplified_CP_SM. In TI device implementations, we've found that some devices with Simplified_CP_SM still benefit from receiving the Prepare command. This patch modifies the code to: 1. Send the Prepare command to all devices, including those with Simplified_CP_SM 2. Ignore errors returned by devices with Simplified_CP_SM that might not support this command This approach maintains compatibility with all devices while ensuring proper functionality of dataport operations for devices that can make use of the Prepare command despite using Simplified_CP_SM. Signed-off-by: Niranjan H Y --- drivers/soundwire/stream.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c index 66ec70930d77ca..9a016f5a722aa7 100644 --- a/drivers/soundwire/stream.c +++ b/drivers/soundwire/stream.c @@ -512,14 +512,19 @@ static int sdw_prep_deprep_slave_ports(struct sdw_bus *bus, sdw_do_port_prep(s_rt, prep_ch, prep ? SDW_OPS_PORT_PRE_PREP : SDW_OPS_PORT_PRE_DEPREP); /* Prepare Slave port implementing CP_SM */ - if (!simple_ch_prep_sm) { - addr = SDW_DPN_PREPARECTRL(p_rt->num); - - if (prep) - ret = sdw_write_no_pm(s_rt->slave, addr, p_rt->ch_mask); - else - ret = sdw_write_no_pm(s_rt->slave, addr, 0x0); + /* For Simplified_CP_SM, MIPI SoundWire specification v1-2 indicates + * Prepare bits are "write-ignored" - this means devices may ignore the command. + * Some devices still benefit from receiving this command even when using + * Simplified_CP_SM, so we send it to all devices and ignore errors from those + * that don't support it. + */ + addr = SDW_DPN_PREPARECTRL(p_rt->num); + if (prep) + ret = sdw_write_no_pm(s_rt->slave, addr, p_rt->ch_mask); + else + ret = sdw_write_no_pm(s_rt->slave, addr, 0x0); + if (!simple_ch_prep_sm) { if (ret < 0) { dev_err(&s_rt->slave->dev, "Slave prep_ctrl reg write failed\n"); @@ -538,6 +543,11 @@ static int sdw_prep_deprep_slave_ports(struct sdw_bus *bus, "Chn prep failed for port %d: %d\n", prep_ch.num, ret); return ret; } + } else { + /* Some device return error for the prepare command, + * ignore the error for Simplified CP_SM + */ + ret = 0; } /* Inform slaves about ports prepared */