From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rodrigo Siqueira Subject: Re: [PATCH V3 4/5] drm/vkms: Compute CRC without change input data Date: Tue, 16 Jul 2019 23:30:24 -0300 Message-ID: <20190717023024.svpgfbzgund2awfw@smtp.gmail.com> References: <20190711082105.GI15868@phenom.ffwll.local> <20190712031449.3pmeimkcde2hrxxh@smtp.gmail.com> <20190716083715.GT15868@phenom.ffwll.local> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============2005163010==" Return-path: Received: from mail-qt1-x841.google.com (mail-qt1-x841.google.com [IPv6:2607:f8b0:4864:20::841]) by gabe.freedesktop.org (Postfix) with ESMTPS id 70A7A6E1C0 for ; Wed, 17 Jul 2019 02:30:31 +0000 (UTC) Received: by mail-qt1-x841.google.com with SMTP id w17so21791220qto.10 for ; Tue, 16 Jul 2019 19:30:31 -0700 (PDT) In-Reply-To: <20190716083715.GT15868@phenom.ffwll.local> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Brian Starkey , Liviu Dudau , Haneen Mohammed , Simon Ser , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org List-Id: dri-devel@lists.freedesktop.org --===============2005163010== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="qp4bmywubblpnone" Content-Disposition: inline --qp4bmywubblpnone Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 07/16, Daniel Vetter wrote: > On Fri, Jul 12, 2019 at 12:14:49AM -0300, Rodrigo Siqueira wrote: > > On 07/11, Daniel Vetter wrote: > > > On Tue, Jun 25, 2019 at 10:38:31PM -0300, Rodrigo Siqueira wrote: > > > > The compute_crc() function is responsible for calculating the > > > > framebuffer CRC value; due to the XRGB format, this function has to > > > > ignore the alpha channel during the CRC computation. Therefore, > > > > compute_crc() set zero to the alpha channel directly in the input > > > > framebuffer, which is not a problem since this function receives a = copy > > > > of the original buffer. However, if we want to use this function in= a > > > > context without a buffer copy, it will change the initial value. Th= is > > > > patch makes compute_crc() calculate the CRC value without modifying= the > > > > input framebuffer. > > >=20 > > > Uh why? For writeback we're writing the output too, so we can write > > > whatever we want to into the alpha channel. For writeback we should n= ever > > > accept a pixel format where alpha actually matters, that doesn't make > > > sense. You can't see through a real screen either, they are all opaqu= e :-) > > > -Daniel > >=20 > > Hmmm, > >=20 > > I see your point and I agree, but even though we can write whatever we > > want in the output, don=E2=80=99t you think that is weird to change the > > framebuffer value in the compute_crc() function? >=20 > Not sure what you mean here ... ? From a quick look the memset only sets > our temporary buffer, so we're not changing the input framebuffer here. > And we have to somehow get rid of the X bits, since there's no alpha > value. For CRC computation, all we need is some value which is the same > for every frame (so that the CRC stays constant for the same visible > output). For writeback we could write whatever we want (which includes > whatever is there already). But there's no guarantee and definitely no > expectation that the X bits survive. Writing 0 is imo the most reasonable > thing to do. I'm not even sure whether modern gpus can still do channel > masking (i.e. only write out specific channels, instead of the entire > color). That was a "feature" of bitop blitters of the 80s/90s :-) > -Daniel Ahhh, now I can see that my mindset was in the 90s :) Thanks =20 > >=20 > > Thanks > > =20 > > > >=20 > > > > Signed-off-by: Rodrigo Siqueira > > > > --- > > > > drivers/gpu/drm/vkms/vkms_composer.c | 31 +++++++++++++++++-------= ---- > > > > 1 file changed, 19 insertions(+), 12 deletions(-) > > > >=20 > > > > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm= /vkms/vkms_composer.c > > > > index 51a270514219..8126aa0f968f 100644 > > > > --- a/drivers/gpu/drm/vkms/vkms_composer.c > > > > +++ b/drivers/gpu/drm/vkms/vkms_composer.c > > > > @@ -6,33 +6,40 @@ > > > > #include > > > > #include > > > > =20 > > > > +static u32 get_pixel_from_buffer(int x, int y, const u8 *buffer, > > > > + const struct vkms_composer *composer) > > > > +{ > > > > + int src_offset =3D composer->offset + (y * composer->pitch) > > > > + + (x * composer->cpp); > > > > + > > > > + return *(u32 *)&buffer[src_offset]; > > > > +} > > > > + > > > > /** > > > > * compute_crc - Compute CRC value on output frame > > > > * > > > > - * @vaddr_out: address to final framebuffer > > > > + * @vaddr: address to final framebuffer > > > > * @composer: framebuffer's metadata > > > > * > > > > * returns CRC value computed using crc32 on the visible portion of > > > > * the final framebuffer at vaddr_out > > > > */ > > > > -static uint32_t compute_crc(void *vaddr_out, struct vkms_composer = *composer) > > > > +static uint32_t compute_crc(const u8 *vaddr, > > > > + const struct vkms_composer *composer) > > > > { > > > > - int i, j, src_offset; > > > > + int x, y; > > > > int x_src =3D composer->src.x1 >> 16; > > > > int y_src =3D composer->src.y1 >> 16; > > > > int h_src =3D drm_rect_height(&composer->src) >> 16; > > > > int w_src =3D drm_rect_width(&composer->src) >> 16; > > > > - u32 crc =3D 0; > > > > + u32 crc =3D 0, pixel =3D 0; > > > > =20 > > > > - for (i =3D y_src; i < y_src + h_src; ++i) { > > > > - for (j =3D x_src; j < x_src + w_src; ++j) { > > > > - src_offset =3D composer->offset > > > > - + (i * composer->pitch) > > > > - + (j * composer->cpp); > > > > + for (y =3D y_src; y < y_src + h_src; ++y) { > > > > + for (x =3D x_src; x < x_src + w_src; ++x) { > > > > /* XRGB format ignores Alpha channel */ > > > > - memset(vaddr_out + src_offset + 24, 0, 8); > > > > - crc =3D crc32_le(crc, vaddr_out + src_offset, > > > > - sizeof(u32)); > > > > + pixel =3D get_pixel_from_buffer(x, y, vaddr, composer); > > > > + bitmap_clear((void *)&pixel, 0, 8); > > > > + crc =3D crc32_le(crc, (void *)&pixel, sizeof(u32)); > > > > } > > > > } > > > > =20 > > > > --=20 > > > > 2.21.0 > > >=20 > > > --=20 > > > Daniel Vetter > > > Software Engineer, Intel Corporation > > > http://blog.ffwll.ch > >=20 > > --=20 > > Rodrigo Siqueira > > https://siqueira.tech >=20 >=20 >=20 > > _______________________________________________ > > dri-devel mailing list > > dri-devel@lists.freedesktop.org > > https://lists.freedesktop.org/mailman/listinfo/dri-devel >=20 >=20 > --=20 > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch --=20 Rodrigo Siqueira https://siqueira.tech --qp4bmywubblpnone Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEE4tZ+ii1mjMCMQbfkWJzP/comvP8FAl0uiEAACgkQWJzP/com vP8X0xAAxp4KZSRHIF9p/L79o4+j8/J2PBMeibgeeQsw2NFfff6rbip2bM4sfccv mjdtxPGJHMUWr/vdeRvokp9kg9QWE/ZOxmX+u07c+/x+qxPhB1/p3uogpNpRvsZ+ SF2xG8riCOmTuKetflJUh7chAm/RDPM/TaajZfUGIIwY9gQm1/C0WyumBp85izpU Nk1dk6Dj/xplD8d+19P7uKgUDc+d3P4ogRbUQKW5NqvgrXyXxa4Zzv1W40BKwsIS jx5xQAqrcQUCkOdPRJyzVMLKBe0kagIEhXMHfSlyn+Nlp47AXYUjMlUV4TuY5980 HsWPGAs98tNpCM+jj1bWxym5F0LnKxyxMqHg62gGQLOWQBVdhWLmYtdCf7bI8A0I 95stQVF6CqWxNzcYJ6ffw6ZFNXKVba6uzrPIAWVwYTvX/JmULM9JzZVMG33vbeYH Yd8grYgJLvRU8k5pc1g5LjXC0+9im1Jr10mmywgUhipErbMxXOfhMuIe2/2lsx5v zkMk/UTlVZQrXxJOw4NUXeb0wDXelrTR3/5cSDT0uMWjSU84AFQLvd5767YxqD+h odiOohM4xAEkB7478GVvwsyjUMf9Tn1QGeWX/m2lsZgv2qYmT5zgVkG1H7jzSEO7 mRzB0k/z3o9M40wzDebVg5TRcyNOdn3+8xKFumWmvmNXuGYMOAU= =ajCg -----END PGP SIGNATURE----- --qp4bmywubblpnone-- --===============2005163010== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KZHJpLWRldmVs IG1haWxpbmcgbGlzdApkcmktZGV2ZWxAbGlzdHMuZnJlZWRlc2t0b3Aub3JnCmh0dHBzOi8vbGlz dHMuZnJlZWRlc2t0b3Aub3JnL21haWxtYW4vbGlzdGluZm8vZHJpLWRldmVs --===============2005163010==--