On 1/8/2025 8:22 PM, Mauro Carvalho Chehab wrote: > 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? > That would not be a correct statement, We don't have issue with using BIT 29 with mask but upper limit of DMA address available to use is 0xdfffffff. Thanks, Dikshita > 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
