RE: [PATCH 1/3] PCI: designware: add accessors for write permission of DBI read-only registers

["Z.q. Hou" <zhiqiang.hou@xxxxxxx>]

Hi Jingoo Han,

Thanks for your comments!

> -----Original Message-----
> From: Jingoo Han [mailto:jingoohan1@xxxxxxxxx]
> Sent: 2017年7月18日 3:41
> To: Z.q. Hou <zhiqiang.hou@xxxxxxx>; 'Joao Pinto'
> <Joao.Pinto@xxxxxxxxxxxx>; linux-pci@xxxxxxxxxxxxxxx;
> bhelgaas@xxxxxxxxxx
> Subject: Re: [PATCH 1/3] PCI: designware: add accessors for write permission
> of DBI read-only registers
> 
> On Tuesday, July 11, 2017 12:11 AM, Z.q. Hou wrote:
> >
> > Hi Bjorn,
> >
> > Due to all Freescale Layerscpe PCIe controllers have to fix the Class
> > code, and this fixup existed in both Layerscape pcie driver and DWC
> > common code, so I want to reuse the fixup in DWC common code.
> > Can you give me any suggestion?
> 
> Please don't add your comment on top of the email.

Ok, got it.

> 
> 
> >
> > > -----Original Message-----
> > > From: Joao Pinto [mailto:Joao.Pinto@xxxxxxxxxxxx]
> > > Sent: 2017年7月7日 16:53
> > > To: Z.q. Hou <zhiqiang.hou@xxxxxxx>; Joao Pinto
> > > <Joao.Pinto@xxxxxxxxxxxx>; linux-pci@xxxxxxxxxxxxxxx;
> > > bhelgaas@xxxxxxxxxx
> > > Cc: jingoohan1@xxxxxxxxx
> > > Subject: Re: [PATCH 1/3] PCI: designware: add accessors for write
> > permission
> > > of DBI read-only registers
> > >
> > >
> > > Hi Zhiqiang,
> > >
> > > Às 4:48 AM de 7/7/2017, Z.q. Hou escreveu:
> > > > Hi Joao,
> > > >
> > > >
> > > >
> > > > Thanks a lot for your comments!
> > > >
> > > >
> > > >
> > > >> -----Original Message-----
> > > >
> > > >> From: Joao Pinto [mailto:Joao.Pinto@xxxxxxxxxxxx]
> > > >
> > > >> Sent: 2017年7月6日 17:44
> > > >
> > > >> To: Z.q. Hou <zhiqiang.hou@xxxxxxx>; linux-pci@xxxxxxxxxxxxxxx;
> > > >
> > > >> Joao.Pinto@xxxxxxxxxxxx
> > > >
> > > >> Cc: bhelgaas@xxxxxxxxxx; jingoohan1@xxxxxxxxx
> > > >
> > > >> Subject: Re: [PATCH 1/3] PCI: designware: add accessors for write
> > > >> permission
> > > >
> > > >> of DBI read-only registers
> > > >
> > > >>
> > > >
> > > >>
> > > >
> > > >> Hi Zhiqiang,
> > > >
> > > >>
> > > >
> > > >> Às 7:33 AM de 7/6/2017, Zhiqiang Hou escreveu:
> > > >
> > > >>> From: Hou Zhiqiang <Zhiqiang.Hou@xxxxxxx>
> > > >
> > > >>>
> > > >
> > > >>> The read-only DBI registers can be written over the DBI when set
> > > >>> the
> > > >
> > > >>> "Write to RO Registers Using DBI" (DBI_RO_WR_EN) field of the
> > > >
> > > >>> MISC_CONTROL_1_OFF register.
> > > >
> > > >>
> > > >
> > > >> I would suggest you to add a cover-letter next time to explain
> > > >> the global
> > > >
> > > >> picture of the patch-set.
> > > >
> > > >
> > > >
> > > > Thanks, I will.
> > > >
> > > >
> > > >
> > > >>
> > > >
> > > >> I understand your need for this patch, but I don't agree on the
> > approach.
> > > >
> > > >
> > > >
> > > > In the DWC common code, there is a function write a DBI read-only
> > register
> > > 'Device class code', and the first 2 patches is to fix it.
> > > >
> > > > The 3rd patch is to refactor the Layerscape PCIe driver's
> > > > host_init
> > function
> > > and reuse the new added accessors.
> > > >
> > > >
> > > >
> > > >> Sometimes the people in charge of the hardware design /
> > > >> configuration, forget
> > > >
> > > >> to specify the device class and that can be problematic for some
> > > >> drivers, and
> > > >
> > > >> so the typical workaround is to set it in the driver using a
> > > >> quirk
> > for example.
> > > >
> > > >>
> > > >
> > > >> You can see some examples here:
> > > >
> > > >> https://urldefense.proofpoint.com/v2/url?u=https-3A__git.kernel.o
> > > >> rg_p
> > > >> ub_scm_linux_kernel_git_torvalds_linux.git_tree_drivers_&d=DwIGaQ
> > > >> &c=D
> > > >>
> > >
> PL6_X_6JkXFx7AXWqB0tg&r=s2fO0hii0OGNOv9qQy_HRXy-xAJUD1NNoEcc3io
> > > _kx0&m
> > > >>
> > >
> =0DrBCvOc_J7LaMXBei1qCXxxfbLxWaVErKZ6Rkm6bUc&s=sOEmExQFqrCEmpA
> > > x9LjSeK
> > > >> RvkW1D-W82ckX5WGCgFWw&e=
> > > >
> > > >> pci/quirks.c
> > > >
> > > >
> > > >
> > > > I don't know the PCI quirks, do you mean remove the pci Device
> > > > Class
> > fix
> > > code from the DWC common code and add it to quirks?
> > > >
> > >
> > > In my opinion adding fixes to a common code is not a good approach.
> > > I
> > would
> > > suggest the fix to go into the quirks file.
> 
> Your answer should be added to here.
> Then, it will help other people follow this email thread.
> 

Yes, and do you know why write to the DBI read-only register(class code) without enable the write permission of DBI read-only registers?
Can you give some suggestions?

Thanks,
Zhiqiang