Em Wed, 8 Jan 2025 16:42:03 +0530 Dikshita Agarwal <quic_dikshita@xxxxxxxxxxx> escreveu: > On 1/8/2025 4:13 PM, Hans Verkuil wrote: > > On 1/8/25 11:21, Dikshita Agarwal wrote: > >> > >> > >> On 1/8/2025 2:25 PM, Hans Verkuil wrote: > >>> On 08/01/2025 09:51, Dikshita Agarwal wrote: > >>>> > >>>> > >>>> On 1/8/2025 1:17 PM, Hans Verkuil wrote: > >>>>> On 08/01/2025 08:43, Dikshita Agarwal wrote: > >>>>>> > >>>>>> > >>>>>> On 1/7/2025 7:27 PM, Nicolas Dufresne wrote: > >>>>>>> Le lundi 23 décembre 2024 à 16:21 +0530, Dikshita Agarwal a écrit : > >>>>>>>> > >>>>>>>> On 12/23/2024 4:00 PM, Mauro Carvalho Chehab wrote: > >>>>>>>>> Em Thu, 12 Dec 2024 17:21:49 +0530 > >>>>>>>>> Dikshita Agarwal <quic_dikshita@xxxxxxxxxxx> escreveu: > >>>>>>>>> > >>>>>>>>>> + .dma_mask = GENMASK(31, 29) - 1, > >>>>>>>>> > >>>>>>>>> Setting a mask to GENMASK() - 1 sounds weird. Is it really what you want? > >>>>>>>>> I so, why? > >>>>>>>>> > >>>>>>>> Hi Mauro, > >>>>>>>> > >>>>>>>> the value of this dma mask should be 0xe0000000 -1. > >>>>>>>> > >>>>>>>> The background for the same is, 0xe0000000 onward memory space is allocated > >>>>>>>> for IO register space so we are restricting the driver buffer allocations > >>>>>>>> to 0xe0000000 - 1. > >>>>>>>> > >>>>>>>> Based on the comments received in the past, we are using GENMASK to > >>>>>>>> generate 0xe0000000. > >>>>>>>> > >>>>>>>> Does this answer your query or I missed something? > >>>>>>> > >>>>>>> I'm not sure it will do what you want. (0xe0000000 -1) matches ~BIT(29). Perhaps > >>>>>>> you wanted to use ~0xe0000000. > >>>>>>> > >>>>>> value of dma mask is coming as expected with GENMASK(31, 29) - 1 > >>>>>> > >>>>>> qcom-iris aa00000.video-codec: dma_mask DFFFFFFF (0xe0000000 -1) > >>>>> > >>>>> Isn't this just the equivalent of GENMASK(28, 0)? Can't you use that? > >>> > >>> Too early in the morning, this suggestion was clearly wrong. > >>> > >>>>> > >>>>> It's much easier to understand than GENMASK()-1. > >>>> > >>>> Sure, I can use either ~GENMASK(29, 29) or ~BIT(29), > >>> > >>> ~BIT(29). > >>> > >>> It's really weird to just disable a single bit, so I think some comments > >>> explaining why this mask is needed would be good (if there aren't comments > >>> already). > >>> > >> I tested this some more, and seems ~BIT(29) doesn't work, as its still > >> conflicting with the register space. > > > > Odd, perhaps a 64 vs 32 bit issue? > > > >> Correct value would be GENMASK(31,30) + GENMASK(28,0) to set the exact bits > >> to get the desired value i.e 0xe0000000 -1 > > Honestly, in this case I would prefer to just go with the actual hex value > > 0xdfffffff together with an explanatory comment. > > > We moved to GENMASK way to address comment on previous version, but sure > can directly use 0xdfffffff with a comment. If I understood it right, bits 0-31 can be used, but the hardware has some issue using bit 29 at the mask. Could you please comment why it can't be used? Btw, as this is a mask, IMO the better would be to document that all bits except for BIT(29) can be used with something like: /* Bit 29 can't be used because ... */ .dma_mask = GENMASK(31, 0) - BIT(29) Thanks, Mauro
