On 10-09-20, 08:53, Pierre-Louis Bossart wrote:
On 9/10/20 1:22 AM, Vinod Koul wrote:
On 09-09-20, 08:48, Pierre-Louis Bossart wrote:
> + * 25 0 (Reserved) > + * 24:22 Function Number [2:0] > + * 21 Entity[6] > + * 20:19 Control Selector[5:4] > + * 18 0 (Reserved) > + * 17:15 Control Number[5:3] > + * 14 Next > + * 13 MBQ > + * 12:7 Entity[5:0] > + * 6:3 Control Selector[3:0] > + * 2:0 Control Number[2:0] > + */ > + > +#define SDW_SDCA_CTL(fun, ent, ctl, ch) \ > + (BIT(30) | \
Programmatically this is fine, but then since we are defining for the description above, IMO it would actually make sense for this to be defined as FIELD_PREP:
FIELD_PREP(GENMASK(30, 26), 1)or better
u32_encode_bits(GENMASK(30, 26), 1)> + FIELD_PREP(GENMASK(24, 22), FIELD_GET(GENMASK(2, 0), (fun))) | \
Why not use u32_encode_bits(GENMASK(24, 22), (fun)) instead for this and below?
Because your comment for the v1 review was to use FIELD_PREP/FIELD_GET, and your other patches for bitfield access only use FIELD_PREP/FIELD_GET.
yes and looking at this, I feel u32_encode_bits(GENMASK(24, 22), (fun)) would look better than FIELD_PREP(GENMASK(24, 22), FIELD_GET(GENMASK(2, 0), (fun)))
Do you agree?
The Function (fun) case is the easy one: the value is not split in two.
But look at the entity case, it's split in two:
FIELD_PREP(BIT(21), FIELD_GET(BIT(6), (ent))) FIELD_PREP(GENMASK(12, 7), FIELD_GET(GENMASK(5, 0), (ent)))
same for control
FIELD_PREP(GENMASK(20, 19), FIELD_GET(GENMASK(5, 4), (ctl))) | FIELD_PREP(GENMASK(6, 3), FIELD_GET(GENMASK(3, 0), (ctl))) |
and same for channel number
FIELD_PREP(GENMASK(17, 15), FIELD_GET(GENMASK(5, 3), (ch))) | FIELD_PREP(GENMASK(2, 0), FIELD_GET(GENMASK(2, 0), (ch))))
I don't see how we can avoid using the FIELD_GET to extract the relevant bits from entity, control, channel number values.
No, you dont need FIELD_GET, that would be pointless for this helper if that was the case
I don't get how one would specify which parts of the original value are extracted?
Or I am missing your point completely.
Correct
It should be:
foo |= u32_encode_bits(val, FOO_MASK_A);which would write val into bits represented by FOO_MASK_A by appropriately shifting val and masking it with FOO_MASK_A
So net result is bits in FOO_MASK_A are modified with val, rest of the bits are not touched
Vinod, please see the explanation below [1], we need to split the original value in two and insert the bits in two separate locations.
You only considered the simple case for the functions, your proposal will not work for entities, controls and channel numbers.
And while at it, consider defining masks for various fields rather than using numbers in GENMASK() above, that would look better, be more readable and people can reuse it.
Actually on this one I disagree. These fields are not intended to be used by anyone, the goal is precisely to hide them behind regmap, and the use of raw numbers makes it easier to cross-check the documentation and the code. Adding a separate set of definitions would not increase readability.
Which one would you prefer:
#define SDCA_FUN_MASK GENMASK(24, 22) foo |= u32_encode_bits(SDCA_FUN_MASK, fun)Or the one proposed...?
Same as above, let's see what this does with the control case where we'd need to have four definitions:
[1]
#define SDCA_CONTROL_DEST_MASK1 GENMASK(20, 19) #define SDCA_CONTROL_ORIG_MASK1 GENMASK(5, 4) #define SDCA_CONTROL_DEST_MASK2 GENMASK(6, 3) #define SDCA_CONTROL_ORIG_MASK2 GENMASK(3, 0)
I think I missed ORIG and DEST stuff, what does this mean here?
Relooking at the bit definition, for example 'Control Number' is defined in both 17:15 as well as 2:0, why is that. Is it split?
How does one program a control number into this?
And the code would look like
foo |= u32_encode_bits(SDCA_CONTROL_DEST_MASK1, FIELD_GET(SDCA_CONTROL_ORIG_MASK1, fun)); foo |= u32_encode_bits(SDCA_CONTROL_DEST_MASK2, FIELD_GET(SDCA_CONTROL_ORIG_MASK2, fun));
The original suggestion was:
FIELD_PREP(GENMASK(20, 19), FIELD_GET(GENMASK(5, 4), (ctl))) | FIELD_PREP(GENMASK(6, 3), FIELD_GET(GENMASK(3, 0), (ctl))) |
I prefer the original... Adding these defines doesn't really add value because a) the values will not be reused anywhere else. b) we need 12 of those defines b) we need a prefix for those defines which makes the code heavier