On 29/07/2024 16:25, Pierre-Louis Bossart wrote:
On 7/29/24 16:01, Krzysztof Kozlowski wrote:
Two bitmasks in 'struct sdw_slave_prop' - 'source_ports' and 'sink_ports' - define which ports to program in sdw_program_slave_port_params(). The masks are used to get the appropriate data port properties ('struct sdw_get_slave_dpn_prop') from an array.
Bitmasks can be non-continuous or can start from index different than 0, thus when looking for matching port property for given port, we must iterate over mask bits, not from 0 up to number of ports.
This fixes allocation and programming slave ports, when a source or sink masks start from further index.
Fixes: f8101c74aa54 ("soundwire: Add Master and Slave port programming") Cc: stable@vger.kernel.org Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org
This is a valid change to optimize how the port are accessed.
But the commit message is not completely clear, the allocation in mipi_disco.c is not modified and I don't think there's anything that would crash. If there are non-contiguous ports, we will still allocate space that will not be initialized/used.
/* Allocate memory for set bits in port lists */ nval = hweight32(prop->source_ports); prop->src_dpn_prop = devm_kcalloc(&slave->dev, nval, sizeof(*prop->src_dpn_prop), GFP_KERNEL); if (!prop->src_dpn_prop) return -ENOMEM;
/* Read dpn properties for source port(s) */ sdw_slave_read_dpn(slave, prop->src_dpn_prop, nval, prop->source_ports, "source");
IOW, this is a valid change, but it's an optimization, not a fix in the usual sense of 'kernel oops otherwise'.
Am I missing something?
BTW, the notion of DPn is that n > 0. DP0 is a special case with different properties, BIT(0) cannot be set for either of the sink/source port bitmask.
I think we speak about two different things. port num > 1, that's correct. But index for src_dpn_prop array is something different. Look at mipi-disco sdw_slave_read_dpn():
173 u32 bit, i = 0; ... 178 addr = ports; 179 /* valid ports are 1 to 14 so apply mask */ 180 addr &= GENMASK(14, 1); 181 182 for_each_set_bit(bit, &addr, 32) { ... 186 dpn[i].num = bit;
so dpn[0..i] = 1..n where i is also the bit in the mask.
Similar implementation was done in Qualcomm wsa and wcd codecs like: array indexed from 0: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/soun...
genmask from 0, with a mistake: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/soun...
The mistake I corrected here: https://lore.kernel.org/all/20240726-asoc-wcd-wsa-swr-ports-genmask-v1-0-d4d...
To summarize, the mask does not denote port numbers (1...14) but indices of the dpn array which are from 0..whatever (usually -1 from port number).
Best regards, Krzysztof