From: "Pavel Machek" <pavel@ucw.cz>
To: cip-dev@lists.cip-project.org
Cc: Pavel Machek <pavel@denx.de>,
Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>,
Biju Das <biju.das.jz@bp.renesas.com>
Subject: Re: [cip-dev] [PATCH 4.19.y-cip 1/6] PCI: rcar: Move shareable code to a common file
Date: Fri, 23 Oct 2020 22:32:57 +0200 [thread overview]
Message-ID: <20201023203257.GA10156@duo.ucw.cz> (raw)
In-Reply-To: <OSBPR01MB5048EA292D626F32EB60B393AA1A0@OSBPR01MB5048.jpnprd01.prod.outlook.com>
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Hi!
> > > +int rcar_pcie_wait_for_dl(struct rcar_pcie *pcie)
> > > +{
> > > + unsigned int timeout = 10000;
> > > +
> > > + while (timeout--) {
> > > + if ((rcar_pci_read_reg(pcie, PCIETSTR) & DATA_LINK_ACTIVE))
> > > + return 0;
> > > +
> > > + udelay(5);
> > > + cpu_relax();
> > > + }
> > > +
> > > + return -ETIMEDOUT;
> > > +}
> >
> > This has same problem. Plus, I don't believe cpu_relax() is good idea
> > there. Relaxing CPU every 5usec will not change anything.
> >
> Agreed (as above). wrt cpu_relax() I believe this was added to improve the performance of other HW threads.
>
Yes, but you'd need to call it in a loop. It will be effective if done
inside udelay(), but not like this.
Best regards,
Pavel
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
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next prev parent reply other threads:[~2020-10-23 20:33 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-23 16:57 [cip-dev] [PATCH 4.19.y-cip 0/6] Add PCIe EP driver to Renesas R-Car Gen3 and RZ/G2x Lad Prabhakar
2020-10-23 16:58 ` [cip-dev] [PATCH 4.19.y-cip 1/6] PCI: rcar: Move shareable code to a common file Lad Prabhakar
2020-10-23 19:40 ` Pavel Machek
2020-10-23 19:58 ` Lad Prabhakar
2020-10-23 20:32 ` Pavel Machek [this message]
2020-10-23 16:58 ` [cip-dev] [PATCH 4.19.y-cip 2/6] PCI: rcar: Fix calculating mask for PCIEPAMR register Lad Prabhakar
2020-10-23 16:58 ` [cip-dev] [PATCH 4.19.y-cip 3/6] dt-bindings: PCI: rcar: Add bindings for R-Car PCIe endpoint controller Lad Prabhakar
2020-10-23 16:58 ` [cip-dev] [PATCH 4.19.y-cip 4/6] PCI: rcar: Add endpoint mode support Lad Prabhakar
2020-10-23 19:41 ` Pavel Machek
2020-10-23 20:16 ` Lad Prabhakar
2020-10-23 20:34 ` Pavel Machek
2020-10-23 16:58 ` [cip-dev] [PATCH 4.19.y-cip 5/6] arm64: defconfig: Enable R-Car PCIe endpoint driver Lad Prabhakar
2020-10-23 16:58 ` [cip-dev] [PATCH 4.19.y-cip 6/6] misc: pci_endpoint_test: Add Device ID for RZ/G2E PCIe controller Lad Prabhakar
2020-10-23 19:36 ` [cip-dev] [PATCH 4.19.y-cip 0/6] Add PCIe EP driver to Renesas R-Car Gen3 and RZ/G2x Pavel Machek
2020-10-23 19:46 ` Lad Prabhakar
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