Re: [PATCH 04/17] media: atomisp: pci: do not use err var when checking port validity for ISP2400

[Tsuchiya Yuto]

On Thu, 2021-10-28 at 12:39 +0100, Mauro Carvalho Chehab wrote:
> Em Thu, 28 Oct 2021 13:12:45 +0900
> Tsuchiya Yuto <kitakar@xxxxxxxxx> escreveu:
> 
> > <Adding back people/list to Cc>
> > 
> > On Tue, 2021-10-26 at 09:26 +0100, Mauro Carvalho Chehab wrote:
> > > Em Mon, 18 Oct 2021 01:19:44 +0900
> > > Tsuchiya Yuto <kitakar@xxxxxxxxx> escreveu:
> > >   
> > > > Currently, the `port >= N_CSI_PORTS || err` checks for ISP2400 are always
> > > > evaluated as true because the err variable is set to `-EINVAL` on
> > > > declaration but the variable is never used until the evaluation.
> > > > 
> > > > Looking at the diff of commit 3c0538fbad9f ("media: atomisp: get rid of
> > > > most checks for ISP2401 version"), the `port >= N_CSI_PORTS` check is
> > > > for ISP2400 and the err variable check is for ISP2401. Fix this issue
> > > > by adding ISP version test there accordingly.
> > > > 
> > > > Yes, there are other better ways to fix this issue, like adding support
> > > > for ISP2400 to ia_css_mipi_is_source_port_valid(). In this way, we can
> > > > unify the following test:
> > > > 
> > > > 	if (!IS_ISP2401)
> > > > 		port = (unsigned int)pipe->stream->config.source.port.port;
> > > > 	else
> > > > 		err = ia_css_mipi_is_source_port_valid(pipe, &port);
> > > > 
> > > > However, the IS_ISP2401 test here (formerly `ifdef ISP2401`) is not
> > > > a result of real hardware difference, but just a result of the following
> > > > two different versions of driver merged by tools [1]:
> > > > 
> > > >   - ISP2400: irci_stable_candrpv_0415_20150521_0458
> > > >   - ISP2401: irci_ecr-master_20150911_0724  
> > > 
> > > No.
> > > 
> > > While I don't have any internal information from the hardware manufacturer,
> > > I guess you misinterpreted things here. 2400 and 2401 are different
> > > hardware versions. See atomisp_pci_probe() logic.
> > > 
> > > Basically, Cherrytail and Anniedale comes with 2401. Older Atom CPUs
> > > (Merrifield and Baytrail) comes with 2400.  
> > 
> > Yes, indeed, 2400 and 2401 are different hardware. When they (I mean who
> > originally wrote atomisp driver non-upstream) needed to distinguish
> > between ISP2400 and ISP2401, they used the ifdefs like the following:
> > 
> >   - USE_INPUT_SYSTEM_VERSION_2    (for both ISP2400/ISP2401)
> >   - USE_INPUT_SYSTEM_VERSION_2401 (for ISP2401)
> >   ...
> > 
> > I think this is a sign that the atomisp driver supports both
> > ISP2400/ISP2401 in a single version.
> 
> Actually, supporting both on a single version is part of Alan's work.
> 
> It seems he used the generation tool to produce a version for 2400, and
> then re-used it to generate for 2401. It then used some scripting tool
> to convert the differences on #ifdef ISP2401. See:
> 
> 	a49d25364dfb ("staging/atomisp: Add support for the Intel IPU v2")
> 
> There are things there like:
> 
> 	+#ifdef ISP2401
> 	+
> 	+#endif
> 
> I did a large cleanup work to get rid of those ifdefs, replacing them
> by runtime logic.
> 
> The end goal is to have a single compile-time driver that works for
> both 2400 and 2401.
> 
> This is not possible yet, as there are some registers that are mapped
> on different addresses, depending on the hardware version, and making
> it generic requires a lot of work and tests. So, for now, we need to 
> have a compile-time option to select between both.
> 
> > Indeed, the upstreamed atomisp uses irci_stable_candrpv_0415_20150521_0458
> > for ISP2400 and IIUC it was working on Bay Trail. On the other hand,
> > intel-aero is a kernel for Cherry Trail and uses the same version
> > irci_stable_candrpv_0415_20150521_0458.
> > 
> > So, both ISP version ISP2400/ISP2401 can be supported by a single
> > driver version.
> 
> I See. OK!
> 
> > > > We should eventually remove (not unify) such tests caused by just a
> > > > driver version difference and use just one version of driver. So, for
> > > > now, let's avoid further unification.
> > > > 
> > > > [1] The function ia_css_mipi_is_source_port_valid() and its usage is
> > > >     added on updating css version to irci_master_20150701_0213
> > > >     https://raw.githubusercontent.com/intel/ProductionKernelQuilts/cht-m1stable-2016_ww31/uefi/cht-m1stable/patches/cam-0439-atomisp2-css2401-and-2401_legacy-irci_master_2015070.patch
> > > >     ("atomisp2: css2401 and 2401_legacy-irci_master_20150701_0213")  
> > > 
> > > What happens is that there is a 2401 and a 2401 "legacy". It sounds
> > > that this due to some different software stacks that are reflected both
> > > at the firmware and at the driver.  
> > 
> > Yeah, I'm not sure what the "legacy" is. It might be a reference of
> > `ISP2401_NEW_INPUT_SYSTEM` (css_2401_csi2p_system) and
> > non-`ISP2401_NEW_INPUT_SYSTEM` (css_2401_system).
> > 
> > > -
> > > 
> > > On other words, this patch requires some rework, as otherwise it will break
> > > support for Baytrail.  
> > 
> > You mean "this patch"? then, I intended this patch is rather a fix for
> > ISP2400 case! The err variable for ISP2400 case is always true because
> > it is not used before the error check:
> > 
> >         int
> >         allocate_mipi_frames(struct ia_css_pipe *pipe,
> >         		     struct ia_css_stream_info *info)
> >         {
> >         	int err = -EINVAL;
> > [...]
> >         	if (!IS_ISP2401)
> >         		port = (unsigned int)pipe->stream->config.source.port.port;
> >         	else
> >         		err = ia_css_mipi_is_source_port_valid(pipe, &port);
> >         
> >         	assert(port < N_CSI_PORTS);
> >         
> >         	if (port >= N_CSI_PORTS || err) {
> >         		ia_css_debug_dtrace(IA_CSS_DEBUG_TRACE_PRIVATE,
> >         				    "allocate_mipi_frames(%p) exit: error: port is not correct (port=%d).\n",
> >         				    pipe, port);
> >         		return -EINVAL;
> >         	}
> > 
> > The first usage of err variable is ia_css_mipi_is_source_port_valid()
> > for IS_ISP2401 case, but it's not used for ISP2400 case. This causes
> > the evaluation `port >= N_CSI_PORTS || err` always true for ISP2400 case,
> > meaning it will be always treated as a error.
> 
> Ok. Had you test the driver with Baytrail?

Unfortunately, no. I don't have a Baytrail device to test (yet?). I
noticed this issue anyway when I tried removing `#ifdef ISP2401`.

This is not directly related to this series, but how we should reduce
the ifdef usage in the future? Here are my two ideas:

  1. (my initial idea) remove `#ifdef ISP2401` part and make ISP2401
     part completely irci_stable_candrpv_0415_20150521_0458

this way does not require (relatively) much human work I think.

But as Mauro says, the `#ifdef ISP2401` part (irci_ecr-master_20150911_0724)
is basically an improved version. So, we may also:

  2. continue unifying `#ifdef ISP2401` and `#ifndef ISP2401` parts

but this way needs more human work I think though. And if we go this
way, I also need to rewrite this patch as mentioned in the commit
message.

> > 
> > > Also, patch 13 should be dropped, as the firmware versions for 2400 are
> > > different  
> > 
> > The firmware version for 2400 on the upstreamed atomisp is
> > irci_stable_candrpv_0415_20150521_0458 :-)
> > 
> >         static const char *isp2400_release_version = STR(irci_stable_candrpv_0415_20150521_0458);
> >         static const char *isp2401_release_version = STR(irci_ecr - master_20150911_0724);
> > 
> > The intention of that patch is rather, it clarifies ISP2401 is now using
> > the same driver (css) version as ISP2400.
> 
> Ok.
> 
> > > - and maybe patches 8 to 12 may need more work in order to not
> > > touch 2400.  
> > 
> > Those patches do not break ISP2400, because what they do for ISP2400
> > is that, they remove members from `struct`s which were initially inside
> > of `ifdef ISP2401`. And because these removed members were initially
> > inside of the ifdefs, the usage was also inside the ifdefs.
> 
> Did you test on Baytrail (ISP2400), and with the compile-time option
> enabled/disabled?

Sorry, I should have clarified on the cover later. For ISP2400, I did
compile test only (CONFIG_VIDEO_ATOMISP_ISP2401 enabled/disabled).

> Regards,
> Mauro