On Mon, May 22, 2023 at 1:59 AM Artur Rojek <contact@xxxxxxxxxxxxxx> wrote:
>
> Consumers expect the buffer to only contain enabled channels. While
> preparing the buffer, the driver makes two mistakes:
> 1) It inserts empty data for disabled channels.
> 2) Each ADC readout contains samples for two 16-bit channels. If either
> of them is active, the whole 32-bit sample is pushed into the buffer
> as-is.
>
> Both of those issues cause the active channels to appear at the wrong
> offsets in the buffer. Fix the above by demuxing samples for active
> channels only.
>
> This has remained unnoticed, as all the consumers so far were only using
> channels 0 and 1, leaving them unaffected by changes introduced in this
> commit.
...
> + u16 tdat[6];
> + u32 val;
> +
> + memset(tdat, 0, ARRAY_SIZE(tdat));
Yeah, as LKP tells us this should be sizeof() instead of ARRAY_SIZE().
> + for (i = 0; mask && i < ARRAY_SIZE(tdat); mask >>= 2) {
> + if (mask & 0x3) {
(for the consistency it has to be GENMASK(), but see below)
First of all, strictly speaking we should use the full mask without
limiting it to the 0 element in the array (I'm talking about
active_scan_mask).
That said, we may actually use bit operations here in a better way, i.e.
unsigned long mask = active_scan_mask[0] & (active_scan_mask[0] - 1);
j = 0;
for_each_set_bit(i, active_scan_mask, ...) {
val = readl(...);
/* Two channels per sample. Demux active. */
tdat[j++] = val >> (16 * (i % 2));
}
> + val = readl(adc->base + JZ_ADC_REG_ADTCH);
> + /* Two channels per sample. Demux active. */
> + if (mask & BIT(0))
> + tdat[i++] = val & 0xffff;
> + if (mask & BIT(1))
> + tdat[i++] = val >> 16;
> + }
> }
--
With Best Regards,
Andy Shevchenko
