linux-kernel - Re: [PATCH] PCI: iproc: Set all 24 bits of PCI class code

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Date:   Mon, 14 Feb 2022 12:49:10 +0100
From:   Pali Rohár <pali@...nel.org>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     Ray Jui <ray.jui@...adcom.com>,
        Roman Bacik <roman.bacik@...adcom.com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        bcm-kernel-feedback-list@...adcom.com, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: iproc: Set all 24 bits of PCI class code

On Friday 11 February 2022 16:23:17 Lorenzo Pieralisi wrote:
> On Wed, Jan 05, 2022 at 07:13:06PM +0100, Pali Rohár wrote:
> > Hello!
> > 
> > On Wednesday 05 January 2022 09:51:48 Ray Jui wrote:
> > > Hi Pali,
> > > 
> > > On 1/5/2022 1:35 AM, Pali Rohár wrote:
> > > > Register 0x43c in its low 24 bits contains PCI class code.
> > > > 
> > > > Update code to set all 24 bits of PCI class code and not only upper 16 bits
> > > > of PCI class code.
> > > > 
> > > > Use a new macro PCI_CLASS_BRIDGE_PCI_NORMAL which represents whole 24 bits
> > > > of normal PCI bridge class.
> > > > 
> > > > Signed-off-by: Pali Rohár <pali@...nel.org>
> > > > 
> > > > ---
> > > > Roman helped me with this change and confirmed that class code is stored
> > > > really in bits [23:0] of custom register 0x43c (normally class code is
> > > > stored in bits [31:8] of pci register 0x08).
> > > > 
> > > > This patch depends on patch which adds PCI_CLASS_BRIDGE_PCI_NORMAL macro:
> > > > https://lore.kernel.org/linux-pci/20211220145140.31898-1-pali@kernel.org/
> > > > ---
> > > >  drivers/pci/controller/pcie-iproc.c | 9 ++++-----
> > > >  1 file changed, 4 insertions(+), 5 deletions(-)
> > > > 
> > > > diff --git a/drivers/pci/controller/pcie-iproc.c b/drivers/pci/controller/pcie-iproc.c
> > > > index 3df4ab209253..2519201b0e51 100644
> > > > --- a/drivers/pci/controller/pcie-iproc.c
> > > > +++ b/drivers/pci/controller/pcie-iproc.c
> > > > @@ -789,14 +789,13 @@ static int iproc_pcie_check_link(struct iproc_pcie *pcie)
> > > >  		return -EFAULT;
> > > >  	}
> > > >  
> > > > -	/* force class to PCI_CLASS_BRIDGE_PCI (0x0604) */
> > > > +	/* force class to PCI_CLASS_BRIDGE_PCI_NORMAL (0x060400) */
> > > >  #define PCI_BRIDGE_CTRL_REG_OFFSET	0x43c
> > > > -#define PCI_CLASS_BRIDGE_MASK		0xffff00
> > > > -#define PCI_CLASS_BRIDGE_SHIFT		8
> > > > +#define PCI_BRIDGE_CTRL_REG_CLASS_MASK	0xffffff
> > > >  	iproc_pci_raw_config_read32(pcie, 0, PCI_BRIDGE_CTRL_REG_OFFSET,
> > > >  				    4, &class);
> > > > -	class &= ~PCI_CLASS_BRIDGE_MASK;
> > > > -	class |= (PCI_CLASS_BRIDGE_PCI << PCI_CLASS_BRIDGE_SHIFT);
> > > > +	class &= ~PCI_BRIDGE_CTRL_REG_CLASS_MASK;
> > > > +	class |= PCI_CLASS_BRIDGE_PCI_NORMAL;
> > > >  	iproc_pci_raw_config_write32(pcie, 0, PCI_BRIDGE_CTRL_REG_OFFSET,
> > > >  				     4, class);
> > > >  
> > > 
> > > I have two comments:
> > > 
> > > 1. You do not seem to generate the email list using the
> > > get_maintainer.pl script, so the two maintainers for Broadcom ARM
> > > architecture (Ray Jui and Scott Branden) are left out.
> > 
> > Ou, sorry for that! I have generated this patch for U-Boot and Linux
> > kernel and probably mixed or forgot to include correct recipients for
> > correct project.
> > 
> > > 2. I suppose 'PCI_CLASS_BRIDGE_PCI_NORMAL' is defined in some common PCI
> > > header in a separate patch as described in the commit message. Then how
> > > come these patches are not constructed with a patch series?
> > 
> > Yes, PCI_CLASS_BRIDGE_PCI_NORMAL is a new constant for common pci header
> > file defined in patch linked in commit message.
> > https://lore.kernel.org/linux-pci/20211220145140.31898-1-pali@kernel.org/
> > 
> > Originally I included this change in v1 of linked patch in December but
> > I realized that it does not match standard PCI config space (different
> > offset 0x43c vs 0x08 and also different shift 0x8 vs 0x0) and probably
> > there is something either incorrect or really non-standard. So later in
> > December I dropped iproc_pcie_check_link() change in v2 of the linked
> > patch where is introduced PCI_CLASS_BRIDGE_PCI_NORMAL and now sent new
> > change for iproc_pcie_check_link() separately.
> > 
> > Technically, linked patch in commit message is just extracting code into
> > the common macros without any functional changed. But change in this
> > iproc_pcie_check_link() has also functional change as now also lower 8
> > bits of class code are changed. So in my opinion this patch should be
> > really separate of linked patch.
> > 
> > I hope that Lorenzo and Bjorn take patches in correct order...
> 
> Can you resend the patches in a series please, I will drop this one.

Done!
https://lore.kernel.org/linux-pci/20220214114109.26809-2-pali@kernel.org/T/#u

> Thanks,
> Lorenzo
> 
> > > Other than, the change itself is exactly what I sent to Roman and looks
> > > good to me. Thanks.
> > > 
> > > Acked-by: Ray Jui <ray.jui@...adcom.com>
> > 
> > Perfect!