Hey Russ, On Mon, Feb 27, 2023 at 10:56:07PM +0000, Conor Dooley wrote: > On Mon, Feb 27, 2023 at 02:42:30PM -0800, Russ Weight wrote: > > On 2/27/23 14:16, Conor Dooley wrote: > > > On Mon, Feb 27, 2023 at 02:04:36PM -0800, Russ Weight wrote: > > >> On 2/24/23 00:28, Conor Dooley wrote: > > >>> On Fri, Feb 24, 2023 at 03:57:09PM +0800, Xu Yilun wrote: > > >>>> On 2023-02-17 at 16:40:17 +0000, Conor Dooley wrote: > > >>>>> This patchset adds support for the "Auto Update" feature on PolarFire > > >>>>> SoC that allows for writing an FPGA bistream to the SPI flash connected > > >>>>> to the system controller. > > >>>> I haven't fully checked the patches yet, just some quick comments: > > >>>> > > >>>> Since this feature is just to R/W the flash, and would not affect the > > >>>> runtime FPGA region, I don't think an FPGA manager is actually needed. > > >>>> Why not just use the MTD uAPI? There is a set of exsiting MTD uAPI & > > >>>> MTD tool if I remember correctly. > > >>> A lack of interest in opening up the system controller to userspace! > > >>> You're right in that the writing of the image can be done that way, and > > >>> while I was testing I used the userspace bits of mtd along the way - but > > >>> for validating that the image we are writing we rely on the system > > >>> controller. > > >>> I'm really not interested in exposing the system controller's > > >>> functionality, especially the bitstream manipulation parts, to userspace > > >>> due to the risk of input validation bugs, so at least that side of > > >>> things should remain in the kernel. > > >>> I suppose I could implement something custom in drivers/soc that does > > >>> the validation only, and push the rest out to userspace. Just seemed > > >>> fitting to do the whole lot in drivers/fpga. > > >> In case you haven't already looked at the new firmware-upload > > >> support in the firmware-loader, I'll give you some references > > >> here to see if it fit you needs. This would only support the > > >> write (not the read) but it would allow the controller to do > > >> validation on the write. > > >> > > >> The is the cover letter which shows a usage example: > > >> https://lore.kernel.org/lkml/20220421212204.36052-1-russell.h.weight@xxxxxxxxx/ > > >> > > >> And this is a pointer to the latest documentation for it: > > >> https://docs.kernel.org/driver-api/firmware/fw_upload.html > > >> > > >> The only current user is: drivers/fpga/intel-m10-bmc-sec-update.c > > > Sounds interesting, I shall go and take a look. Just quickly, when you > > > say it wouldn't support the read, what exactly do you mean? > > > The only read that I am really interested in doing is reading the first > > > 1K of flash as I need to RMW it, but I don't think that that's what you > > > mean. > > > Do you mean that I would not be able to dump the firmware using your > > > fw_upload interface? If so, that's an acceptable constraint IMO. > > > > Yes - I mean that you couldn't dump the firmware image from userspace > > using the fw_upload interface. The sysfs interface allows you to read > > and write a temporary buffer, but once you "echo 0 > loading", there > > is no sysfs interface associated with the firmware-loader that would > > allow you to read the image from flash. Your controller actually does > > the writes, so RMW in that context is fine. > > Ahh cool. I don't really care about dumping the firmware via such a > mechanism, so that sounds good to me. > I'll check out your approach, the immediate thought is that it sounds > suitable to my use case, so thanks! Taken me a while to get around to it, but thanks for your suggestion. Looks like it is suitable for what I am trying to do, so in the middle of working on another version of this using fw_upload. The enum return codes from write are a little clumsy, but oh well, could be worse I suppose. Just one thing I noted (although I rarely pay much attention to/rely on the driver-api docs when recent drivers exist as usable examples) is that the docs for this stuff is a wee bit out of date due to some API changes. In the code example in this document: https://docs.kernel.org/driver-api/firmware/fw_upload.html firmware_upload_register() has fewer arguments than it does when you look at the signature of the function in the documentation right below it. Cheers, Conor.
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