Messages in this thread |  | | Date | Wed, 24 Jun 2009 09:12:20 +0200 | From | Andi Kleen <> | Subject | Re: [PATCH 3/8] SFI: core support |
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On Wed, Jun 24, 2009 at 11:34:40AM +0800, Feng Tang wrote: > > > > +static void __iomem *sfi_map_memory(u32 phys, u32 size) > > > +{ > > > + if (!phys || !size) > > > + return NULL; > > > + > > > + if (sfi_tbl_permanant_mapped) > > > > > > > > > + return ioremap((unsigned long)phys, size); > > > + else > > > + return arch_early_ioremap((unsigned long)phys, > > > size); +} > > > > imho it would be cleaner if the callers just called these functions > > directly. Are the !phys !size checks really needed? > > Andi, > > Thanks for many good comments, will address them. > > For this question, this sfi_map_memory() may get called before and after > the ioremap() is ready, so we add a permanent flag to judge the
Yes, but the callers should know this and they can call the right function. I suspect only very few callers will need the early variant.
> environment and chose the right API automatically. e.g. after system is > booted, cpu freq driver will implicitly call this API to get freq info
cpufreq driver shouldn't be initialized before ioremap
> > > > Since the mappings are always 4K you would only need to remap > > if the size is > PAGE_SIZE > > yes, some of the table may be in one page, but some may not start at page > boundary and cross pages, we do it this way as this map/unmap/remap/unmap > routine only happen few times in boot phase.
The TLB flushes tend to be a few thousand cycles at least.
It's not much, but with all the recent focus on faster boot times it's still better to not write unnecessarily inefficient initialization code.
> > > > > > + > > > + if (sfi_tb_verify_checksum(table, length)) > > > + goto unmap_and_exit; > > > + > > > + /* Initialize sfi_tblist entry */ > > > + sfi_tblist.tables[sfi_tblist.count].flags = flags; > > > + sfi_tblist.tables[sfi_tblist.count].address = addr; > > > + sfi_tblist.tables[sfi_tblist.count].pointer = NULL; > > > + memcpy(&sfi_tblist.tables[sfi_tblist.count].header, > > > + table, sizeof(struct sfi_table_header)); > > > > To be honest I'm not sure why this list exists at all. > > Is it that difficult to just rewalk the firmware supplied > > table as needed? > > Currently, there are about 10 SFI tables (more are expected), and most of > them will be parsed in driver initialization phase, like timer/cpu idle/ > cpu frequency/rtc/system wake driver. Using a global list may save some > system overhead
Walking the tables as they are laid out in memory should be quite equivalent to walking a list, shouldn't it?
It would be only a relatively small simplification agreed, but if you're claiming to do a "Simple Firmware Interface" imho you should try to make it as simple possible, and that includes not setting up redundant data structures.
-Andi -- ak@linux.intel.com -- Speaking for myself only.
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