> -----Original Message----- > From: Palmer Dabbelt <palmer@xxxxxxxxxxx> > Sent: Wednesday, September 9, 2020 8:42 AM > To: Christoph Hellwig <hch@xxxxxxxxxxxxx>; Dhananjay Vilasrao Kangude > <dkangude@xxxxxxxxxxx> > Cc: yash.shah@xxxxxxxxxx; robh+dt@xxxxxxxxxx; Paul Walmsley > <paul.walmsley@xxxxxxxxxx>; bp@xxxxxxxxx; mchehab@xxxxxxxxxx; > tony.luck@xxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; aou@xxxxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; sachin.ghadi@xxxxxxxxxx; > rrichter@xxxxxxxxxxx; james.morse@xxxxxxx; linux- > riscv@xxxxxxxxxxxxxxxxxxx; linux-edac@xxxxxxxxxxxxxxx > Subject: Re: [PATCH v2 2/3] soc: sifive: Add SiFive specific Cadence DDR > controller driver > > EXTERNAL MAIL > > > On Sun, 06 Sep 2020 23:11:26 PDT (-0700), Christoph Hellwig wrote: > > On Mon, Sep 07, 2020 at 11:17:58AM +0530, Yash Shah wrote: > >> Add a driver to manage the Cadence DDR controller present on SiFive > >> SoCs At present the driver manages the EDAC feature of the DDR > controller. > >> Additional features may be added to the driver in future to control > >> other aspects of the DDR controller. > > > > So if this is a generic(ish) Cadence IP block shouldn't it be named > > Cadence and made generic? Or is the frontend somehow SiFive specific? > > For some reason I thought we had a SiFive-specific interface to this, but I may > have gotten that confused with something else as it's been a while. Someone > from SiFive would probably have a better idea, but it looks like the person I'd > ask isn't thereany more so I'm all out of options ;) > > It looks like there was a very similar driver posted by Dhananjay Kangude > from Cadence in April: > https://urldefense.com/v3/__https://lkml.org/lkml/2020/4/6/358__;!!EHscm > S1ygiU1lA!UfVYWzQqCgaUNKN156ffKM5NkFoYtPhHapruC3yqme7nvbUBnD2 > mEHg8F6it4y4$ . Some of the register definitions seem to be different, but > the code I looked at is very similar so there's at least some bits that could be > shared. I found a v4 of that patch set, but that was back in May: > https://urldefense.com/v3/__https://lkml.org/lkml/2020/5/11/912__;!!EHsc > mS1ygiU1lA!UfVYWzQqCgaUNKN156ffKM5NkFoYtPhHapruC3yqme7nvbUBnD > 2mEHg8DeCwApk$ . It alludes to a v5, but I can't find one. I've added > Dhananjay, maybe he knows what's up? > > I don't know enough about the block to know if the subtle difference in > register names/offsets means. They look properly jumbled up (ie, not just an > offset), so maybe there's just different versions or that's the SiFive-specific > part I had bouncing around my head? Either way, it seems like one driver > with some simple configuration could handle both of these -- either sticking > the offsets in the DT (if they're going to be different everywhere) or by > coming up with some version sort of thing (if there's a handful of these). > > I'm now also a bit worried about the provenace of this code. The two drivers > are errily similar -- for example, the variable definitions in handle_ce() > > u64 err_c_addr = 0x0; > u64 err_c_data = 0x0; > u32 err_c_synd, err_c_id; > u32 sig_val_l, sig_val_h; > > are exactly the same. [Dhananjay Kangude] Hi Palmer, Sorry for delayed reply. I was expecting new changes into the hardware IP since last couple of months thus I haven't up streamed V5 patch till now. The cadence driver version is of more generic for cadence DDR controllers which could be part of other SoCs too. I would suggest Yash to patch Sifive specific changes once cadence DDR controller driver get up streamed. I will send V5 in coming days. Thank, Dhananjay
