Messages in this thread | | | From | Andy Shevchenko <> | Date | Sat, 13 Nov 2021 15:15:41 +0200 | Subject | Re: [PATCH 4/4] spi: dw: Add Synopsys Component version reading and parsing |
| |
On Sat, Nov 13, 2021 at 2:19 AM Serge Semin <fancer.lancer@gmail.com> wrote: > On Sat, Nov 13, 2021 at 01:14:30AM +0200, Andy Shevchenko wrote: > > On Saturday, November 13, 2021, Serge Semin <fancer.lancer@gmail.com> wrote: > > > On Fri, Nov 12, 2021 at 11:37:36PM +0200, Andy Shevchenko wrote: > > > > On Fri, Nov 12, 2021 at 11:27 PM Andy Shevchenko > > > > <andy.shevchenko@gmail.com> wrote: > > > > > On Fri, Nov 12, 2021 at 10:52 PM Serge Semin > > > > > <Sergey.Semin@baikalelectronics.ru> wrote:
...
> > > > > > + /* > > > > > > + * Retrieve the Synopsys component version if it hasn't been > > > specified > > > > > > + * by the platform. Note the CoreKit version ID is encoded > > > as a 4bytes > > > > > > + * ASCII string enclosed with '*' symbol. > > > > > > + */ > > > > > > + if (!dws->ver) { > > > > > > + u32 comp; > > > > > > + > > > > > > + comp = dw_readl(dws, DW_SPI_VERSION); > > > > > > + dws->ver = (DW_SPI_GET_BYTE(comp, 3) - '0') * 100; > > > > > > + dws->ver += (DW_SPI_GET_BYTE(comp, 2) - '0') * 10; > > > > > > + dws->ver += (DW_SPI_GET_BYTE(comp, 1) - '0'); > > > > > > + > > > > > > + dev_dbg(dev, "Synopsys DWC%sSSI v%u.%02u\n", > > > > > > + (dws->caps & DW_SPI_CAP_DWC_HSSI) ? " " : " > > > APB ", > > > > > > + dws->ver / 100, dws->ver % 100); > > > > > > > > > > > > > Oh lą lą, first you multiply then you divide in the same piece of code! > > > > > What's wrong with fourcc (and thus keep it in ver filed as is) ? (Also > > > > > we have %p4cc) > > > > > > Please note that's just a dev_DBG() print. So division has been used > > > in there to check whether the conversion was correct. The whole idea > > > behind the code above it was to retrieve the Component version as a > > > single number so then it could be used by the driver code in a simple > > > statement with a normal integer operation. For instance in case if we > > > need to check whether DW SSI IP-core version is greater than 1.01 we'd > > > have something like this: if (dws->ver > 101). Here 101 looks at least > > > close to the original 1.01. How would the statement look with four > > > chars? Of course we could add an another macro which would look like > > > this: > > > #define DW_SSI_VER(_maj, _mid, _min) \ > > > ((_maj) << 24 | (_mid) << 16 | (_min) << 8 | '*') > > > and use it with raw version ID, like this > > > (dws->ver > DW_SSI_VER('1', '0', '1')). But IMO it doesn't look > > > better if not worse. > > > Alternatively we could split the version ID into two parts with > > > major and minor numbers. But normally one doesn't make much sense > > > without another so each statement would need to check both of them > > > at once anyway. So I decided to stick with a simplest solution and > > > combined them into a single storage. Have you got a better idea of > > > how to implement this functionality? > > > Then check DWC3 driver which relies on IZp version a lot. > > I'm still not convinced that the DWC3 solution would be better in this case. > (I had a similar approach in mind though.) Although it might be suitable > here seeing we could take the IP generation into account in a single > macro. But at the same time having macros defined for each version may > eventually turn into a clumsy set of macros space as it happened in DWC3. > > I don't understand what do you see wrong in the suggested here > solution except a math in the debug string?
The transformation ruins the fourcc [1] representation. We know that this is an ASCII. We know the position and meaning of each from 4 characters.
[1]: https://en.wikipedia.org/wiki/FourCC
> Why would you prefer the > DWC3 approach better than the one implemented in my patch?
You asked what is _better_ implementation than yours. It doesn't mean the DWC3 approach fully fits here, but - SPI DW has the same issue as DWC3 solves, i.e. different version lines for two or more IPs of the same kind (see DWC3, DWC31, DWC32) - it doesn't ruins 4cc
In case if we need to print it, I would rather see something in %p4cc implementation than customized 100500 approaches spreaded over the entire kernel.
> I don't really see much benefits in it: > if (dws->ver > 101) > or > if (DW_SPI_VER_AFTER(dws, 101)) > In both cases version ID isn't represented in the original > Vendor-defined structure, like "1.01". The only part which could be > considered as better in DWC3 approach is having a macro name, which gives > a bit better notion about the operation. But does it really worth > introducing a new abstraction in the driver? > > On the other hand we could intermix the approaches. For instance decode > the Component version as I suggested in this patch and implement a set of > version checking macro. Thus we won't need so many additional macro > encoding the SSI_COMP_VERSION content. > > If only we could have a macro like DW_SPI_VER(dws, >=, "1.01a") with no > performance drawbacks I'd be glad to use it. AFAIU compiler can't > operate with the string literal symbols, thus the symbols extraction > like "1.01a"[0] will be performed on each statement execution which isn't > that performant comparing to a simple two integers comparison. > > BTW note the DWC3 macros implicitly depend on having a local variable > with dwc name which violates the kernel coding style.
> > > > > > + } > > > > > > > Have you seen this, btw? > > > > > > > > https://elixir.bootlin.com/linux/latest/source/drivers/ > > > tty/serial/8250/8250_dwlib.c#L93 > > > > > > It doesn't utilized version ID for something functional, but just > > > prints it to the console. So it isn't that good reference in this > > > case.
Depends what you would like to do with this. If it's only for information to the developer, then it fits, if you need to compare, then see above.
-- With Best Regards, Andy Shevchenko
| |