Messages in this thread Patch in this message | | | Subject | Re: [Intel-wired-lan] [PATCH] driver core: fix e1000e ltr bug | From | "Neftin, Sasha" <> | Date | Wed, 30 Jun 2021 09:13:36 +0300 |
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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 <sasha.neftin@intel.com <mailto:sasha.neftin@intel.com>> > 于 2021年6月29日周二 22:49写道: > > 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 <seven.yi.lee@gmail.com > <mailto:seven.yi.lee@gmail.com>> > > --- > > 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 >
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