From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neftin, Sasha Date: Thu, 1 Jul 2021 11:34:49 +0300 Subject: [Intel-wired-lan] [PATCH] driver core: fix e1000e ltr bug In-Reply-To: References: <20210629082128.255988-1-seven.yi.lee@gmail.com> <02ff77ef-e802-8e13-d169-1ab2c250405a@intel.com> <0234b97a-f207-47b0-1545-582ee5282824@intel.com> Message-ID: <1e15c452-f8be-85fa-e424-b7463cc703eb@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: intel-wired-lan@osuosl.org List-ID: On 6/30/2021 09:26, Yee Li wrote: > I agree with you. > That's better code. Thank Yee-Li for discovering this problem. I would suggest we (intel) will process a patch to address this problem. Can I put you kindly as "Suggested-by"? > > Neftin, Sasha > > ?2021?6?30??? ??2:13??? > > On 6/29/2021 20:33, Yee Li wrote: > > > > Yes, 18874368ns > 3145728ns. > > But, 0xe40 < 0x1003. > I got you. I would agree, direct comparison is error-prone. (10M is > impacted) > I would suggest do not use convert function. lat_en should rather > presented as lat_enc = scale x value: > Introduce two u16 variables, u16 lat_enc_d and u16 max_ltr_enc_d; > > lat_enc_d = (lat_enc & 0x0x3ff) x (1U << 5*((max_ltr_enc & 0x1c00) > >> 10)) > > max_ltr_enc_d = (max_ltr_enc & 0x0x3ff) x (1U << 5*((max_ltr_enc & > 0x1c00) >> 10)) > > Then: > if (lat_enc_d > max_ltr_enc_d) > ? ? ? ? lat_enc = max_ltr_enc; > what do you think? > > > > > So, the final lat_enc is 0xe40. > > (Latency encoded is less than maximum LTR encoded by platform) > > > > Neftin, Sasha >> > > ? 2021?6?29??? 22:49??? > > > >? ? ?On 6/29/2021 11:21, YeeLi wrote: > >? ? ?Yeeli, > >? ? ? > In e1000e driver, a PCIe-like device, the max > snoop/no-snoop latency > >? ? ? > is the upper limit.So, directly compare the size of > lat_enc and > >? ? ? > max_ltr_enc is incorrect. > >? ? ? > > >? ? ?why? > >? ? ? >? ? ? In 1000Mbps, 0x8b9 < 0x1003, 189440 ns < 3145728 ns, > correct. > >? ? ? > > >? ? ? >? ? ? In 100Mbps, 0xc3a < 0x1003, 1900544 ns < 3145728 ns, > correct. > >? ? ? > > >? ? ? >? ? ? In 10Mbps, 0xe40 < 0x1003, 18874368 > 3145728, incorrect. > >? ? ? > > >? ? ?Platform LTR encoded is 0x1003 - right. It is meant 1048576ns > x 3 = > >? ? ?3145738ns. > >? ? ?Now, > >? ? ?for 1000M: 0x08b9 => 185ns x 1024 = 189440ns (you are correct) > >? ? ?for 100M: 0x0c3a => 58ns x 32768 = 1900544ns (correct) > >? ? ?for 10M: 0x0e41 => 577ns x 32768 = 18907136ns (ok?) > >? ? ?18907136ns > 3145738ns, (latency encoded is great than > maximum LTR > >? ? ?encoded by platform) - so, there is no point to wait more > than platform > >? ? ?required, and lat_enc=max_ltr_enc. It is expected and we sent > right > >? ? ?value to the power management controller. > >? ? ?What is the problem you try solve? > > > >? ? ? > Decoded the lat_enc and max_ltr_enc before compare them is > necessary. > >? ? ? > > >? ? ? > Signed-off-by: YeeLi > >? ? ?>> > >? ? ? > --- > >? ? ? >? ?drivers/net/ethernet/intel/e1000e/ich8lan.c | 23 > >? ? ?++++++++++++++++++++- > >? ? ? >? ?1 file changed, 22 insertions(+), 1 deletion(-) > >? ? ? > > >? ? ? > diff --git a/drivers/net/ethernet/intel/e1000e/ich8lan.c > >? ? ?b/drivers/net/ethernet/intel/e1000e/ich8lan.c > >? ? ? > index 590ad110d383..3bff1b570b76 100644 > >? ? ? > --- a/drivers/net/ethernet/intel/e1000e/ich8lan.c > >? ? ? > +++ b/drivers/net/ethernet/intel/e1000e/ich8lan.c > >? ? ? > @@ -986,6 +986,27 @@ static s32 > e1000_k1_workaround_lpt_lp(struct > >? ? ?e1000_hw *hw, bool link) > >? ? ? >? ? ? ?return ret_val; > >? ? ? >? ?} > >? ? ? > > >? ? ? > +static u32 convert_e1000e_ltr_scale(u32 val) > >? ? ? > +{ > >? ? ? > +? ? ?if (val > 5) > >? ? ? > +? ? ? ? ? ? ?return 0; > >? ? ? > + > >? ? ? > +? ? ?return 1U << (5 * val); > >? ? ? > +} > >? ? ? > + > >? ? ? > +static u64 decoded_ltr(u32 val) > >? ? ? > +{ > >? ? ? > +? ? ?u64 decoded_latency; > >? ? ? > +? ? ?u32 value; > >? ? ? > +? ? ?u32 scale; > >? ? ? > + > >? ? ? > +? ? ?value = val & 0x03FF; > >? ? ? > +? ? ?scale = (val & 0x1C00) >> 10; > >? ? ? > +? ? ?decoded_latency = value * > convert_e1000e_ltr_scale(scale); > >? ? ? > + > >? ? ? > +? ? ?return decoded_latency; > >? ? ? > +} > >? ? ? > + > >? ? ? >? ?/** > >? ? ? >? ? *? e1000_platform_pm_pch_lpt - Set platform power > management > >? ? ?values > >? ? ? >? ? *? @hw: pointer to the HW structure > >? ? ? > @@ -1059,7 +1080,7 @@ static s32 > e1000_platform_pm_pch_lpt(struct > >? ? ?e1000_hw *hw, bool link) > >? ? ? >? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? E1000_PCI_LTR_CAP_LPT + 2, > >? ? ?&max_nosnoop); > >? ? ? >? ? ? ? ? ? ? ?max_ltr_enc = max_t(u16, max_snoop, > max_nosnoop); > >? ? ? > > >? ? ? > -? ? ? ? ? ? ?if (lat_enc > max_ltr_enc) > >? ? ? > +? ? ? ? ? ? ?if (decoded_ltr(lat_enc) > > decoded_ltr(max_ltr_enc)) > >? ? ? >? ? ? ? ? ? ? ? ? ? ? ?lat_enc = max_ltr_enc; > >? ? ? >? ? ? ?} > >? ? ? > > >? ? ? > > >? ? ?sasha > > > sasha