Date: Fri, 25 Jan 2013 22:48:21 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Taku YAMAMOTO <taku@tackymt.homeip.net> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: [PATCH] to fix slow gen2 Intel video (i830, i845, i85x, i865) with KMS Message-ID: <20130125204821.GY2522@kib.kiev.ua> In-Reply-To: <20130126050654.37ac83fd477464a911b49bf6@tackymt.homeip.net> References: <20130126050654.37ac83fd477464a911b49bf6@tackymt.homeip.net>
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On Sat, Jan 26, 2013 at 05:06:54AM +0900, Taku YAMAMOTO wrote:
> Hi all,
>=20
> A good news to owners of i830, i845, i852, i855 and i865 (a.k.a. gen2),
> who've got frustrated with the bad performance with KMS.
>=20
> I managed to track down the root cause of the slowness of gen2 with KMS a=
nd
> finally fixed it.
> The attached one-liner patch is the fix.
> (It was my surprise that the actual problem lied in agp rather than i915k=
ms.)
>=20
> --=20
> -|-__ YAMAMOTO, Taku
> | __ < <taku@tackymt.homeip.net>
>=20
> - A chicken is an egg's way of producing more eggs. -
> --- sys/dev/agp/agp_i810.c.orig 2013-01-20 16:18:33.382363986 +0900
> +++ sys/dev/agp/agp_i810.c 2013-01-25 05:47:17.046570619 +0900
> @@ -2228,7 +2228,7 @@ agp_i830_chipset_flush(device_t dev)
> bus_write_4(sc->sc_res[0], AGP_I830_HIC, hic | (1 << 31));
> for (i =3D 0; i < 20000 /* 1 sec */; i++) {
> hic =3D bus_read_4(sc->sc_res[0], AGP_I830_HIC);
> - if ((hic & (1 << 31)) !=3D 0)
> + if ((hic & (1 << 31)) =3D=3D 0)
> break;
> DELAY(50);
> }
This looks right, comparing our (mine) code and the Linux intel-gtt.c.
Thank you for tracking it down.
Unfortunately, this magic is not documented at all. The 855GM datasheet
I have completely omits a description for the register 0x70 of the host
bridge. The only reference we are allowed to see is in the Linux agp
driver source.
I will wait a little before committing, in the hope that someone gives
the change an additional test.
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