From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 1/2] drm/i915: Use mul_u32_u32() for 32b x 32b -> 64b result
Date: Wed, 13 Sep 2017 14:51:55 +0300 [thread overview]
Message-ID: <20170913115155.GH4914@intel.com> (raw)
In-Reply-To: <20170913105154.2910-1-chris@chris-wilson.co.uk>
On Wed, Sep 13, 2017 at 11:51:53AM +0100, Chris Wilson wrote:
> As realised by commit 9e3d6223d209 ("math64, timers: Fix 32bit
> mul_u64_u32_shr() and friends"), GCC does not always generate ideal code
> for performing a 32b x 32b multiply returning a 64b result (i.e. where
> we idiomatically use u64 result = (u64)x * (u32)x). This catches a
> couple of instances in the display code using (u64)x * (u32)y.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/i915/intel_display.c | 2 +-
> drivers/gpu/drm/i915/intel_tv.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 6b3de6ad86d3..8f19d0b3512e 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -10223,7 +10223,7 @@ int intel_dotclock_calculate(int link_freq,
> if (!m_n->link_n)
> return 0;
>
> - return div_u64((u64)m_n->link_m * link_freq, m_n->link_n);
> + return div_u64(mul_u32_u32(m_n->link_m, link_freq), m_n->link_n);
> }
>
> static void ironlake_pch_clock_get(struct intel_crtc *crtc,
> diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
> index 0cc999fa09c5..a79a7591b2cf 100644
> --- a/drivers/gpu/drm/i915/intel_tv.c
> +++ b/drivers/gpu/drm/i915/intel_tv.c
> @@ -1385,7 +1385,7 @@ intel_tv_get_modes(struct drm_connector *connector)
> mode_ptr->vsync_end = mode_ptr->vsync_start + 1;
> mode_ptr->vtotal = vactive_s + 33;
>
> - tmp = (u64) tv_mode->refresh * mode_ptr->vtotal;
> + tmp = mul_u32_u32(tv_mode->refresh, mode_ptr->vtotal);
> tmp *= mode_ptr->htotal;
> tmp = div_u64(tmp, 1000000);
> mode_ptr->clock = (int) tmp;
> --
> 2.14.1
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Ville Syrjälä
Intel OTC
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
next prev parent reply other threads:[~2017-09-13 11:51 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-13 10:51 [PATCH 1/2] drm/i915: Use mul_u32_u32() for 32b x 32b -> 64b result Chris Wilson
2017-09-13 10:51 ` [PATCH 2/2] drm/i915/selftests: " Chris Wilson
2017-09-13 11:53 ` Ville Syrjälä
2017-09-13 11:22 ` ✗ Fi.CI.BAT: failure for series starting with [1/2] drm/i915: " Patchwork
2017-09-13 13:54 ` Chris Wilson
2017-09-13 11:51 ` Ville Syrjälä [this message]
-- strict thread matches above, loose matches on Subject: below --
2017-07-20 11:15 [PATCH 1/2] " Chris Wilson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170913115155.GH4914@intel.com \
--to=ville.syrjala@linux.intel.com \
--cc=chris@chris-wilson.co.uk \
--cc=intel-gfx@lists.freedesktop.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox