> -----Original Message-----
> From: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> Sent: Tuesday, September 3, 2024 8:50 PM
> To: Liao, Bard <yung-chuan.liao@xxxxxxxxxxxxxxx>; Vinod Koul
> <vkoul@xxxxxxxxxx>; Pierre-Louis Bossart <pierre-
> louis.bossart@xxxxxxxxxxxxxxx>
> Cc: Kale, Sanyog R <sanyog.r.kale@xxxxxxxxx>; Shreyas NC
> <shreyas.nc@xxxxxxxxx>; alsa-devel@xxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx; Liao, Bard
> <bard.liao@xxxxxxxxx>
> Subject: Re: [PATCH] soundwire: stream: fix programming slave ports for non-
> continous port maps
>
> On 03/09/2024 09:34, Liao, Bard wrote:
> >
> > On 7/31/2024 2:56 PM, Vinod Koul wrote:
> >> On 29-07-24, 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@xxxxxxxxxxxxxxx>
> >>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> >>> 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.
> >> The fix seems right to me, we cannot have assumption that ports are
> >> contagious, so we need to iterate over all valid ports and not to N
> >> ports which code does now!
> >
> >
> > Sorry to jump in after the commit was applied. But, it breaks my test.
> >
> > The point is that dpn_prop[i].num where the i is the array index, and
> >
> > num is the port number. So, `for (i = 0; i < num_ports; i++)` will iterate
>
> Please fix your email client so it will write proper paragraphs.
> Inserting blank lines after each sentence reduces the readability.
>
> >
> > over all valid ports.
> >
> > We can see in below drivers/soundwire/mipi_disco.c
> >
> > nval = hweight32(prop->sink_ports);
> >
> > prop->sink_dpn_prop = devm_kcalloc(&slave->dev, nval,
> >
> > sizeof(*prop->sink_dpn_prop),
> >
> > GFP_KERNEL);
> >
> > And sdw_slave_read_dpn() set data port properties one by one.
> >
> > `for_each_set_bit(i, &mask, 32)` will break the system when port numbers
>
> The entire point of the commit is to fix it for non-continuous masks.
> And I tested it with non-continuous masks.
>
> >
> > are not continuous. For example, a codec has source port number = 1 and 3,
>
> Which codec? Can you give a link to exact line in *UPSTREAM* kernel.
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/sound/soc/codecs/rt722-sdca-sdw.c#n217
prop->source_ports = BIT(6) | BIT(2); /* BITMAP: 01000100 */
prop->sink_ports = BIT(3) | BIT(1); /* BITMAP: 00001010 */
>
> >
> > then dpn_prop[0].num = 1 and dpn_prop[1].num = 3. And we need to go
> >
> > throuth dpn_prop[0] and dpn_prop[1] instead of dpn_prop[1] and
> dpn_prop[3].
> >
>
> What are the source or sink ports in your case? Maybe you just generate
> wrong mask?
I checked my mask is 0xa when I do aplay and it matches the sink_ports of
the rt722 codec.
>
> It's not only my patch which uses for_each_set_bit(). sysfs_slave_dpn
> does the same.
What sysfs_slave_dpn does is
i = 0;
for_each_set_bit(bit, &mask, 32) {
if (bit == N) {
return sprintf(buf, format_string,
dpn[i].field);
}
i++;
}
It uses a variable "i" to represent the array index of dpn[i].
But, it is for_each_set_bit(i, &mask, 32) in your patch and the variable "i"
which represents each bit of the mask is used as the index of dpn_prop[i].
Again, the point is that the bits of mask is not the index of the dpn_prop[]
array.
>
> Best regards,
> Krzysztof
