Messages in this thread | | | Subject | Re: [PATCH V3 11/14] coresight: sink: Add TRBE driver | From | Anshuman Khandual <> | Date | Mon, 15 Feb 2021 14:56:54 +0530 |
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On 2/12/21 10:27 PM, Mathieu Poirier wrote: > [...] > >>> >>> >>>> + if (nr_pages < 2) >>>> + return NULL; >>>> + >>>> + buf = kzalloc_node(sizeof(*buf), GFP_KERNEL, trbe_alloc_node(event)); >>>> + if (IS_ERR(buf)) >>>> + return ERR_PTR(-ENOMEM); >>>> + >>>> + pglist = kcalloc(nr_pages, sizeof(*pglist), GFP_KERNEL); >>>> + if (IS_ERR(pglist)) { >>>> + kfree(buf); >>>> + return ERR_PTR(-ENOMEM); >>>> + } >>>> + >>>> + for (i = 0; i < nr_pages; i++) >>>> + pglist[i] = virt_to_page(pages[i]); >>>> + >>>> + buf->trbe_base = (unsigned long) vmap(pglist, nr_pages, VM_MAP, PAGE_KERNEL); >>>> + if (IS_ERR((void *)buf->trbe_base)) { >>> >>> Why not simply make buf->trbe_base a void * instead of having to do all this >> >> There are many arithmetic and comparison operations involving trbe_base >> element. Hence it might be better to keep it as unsigned long, also to >> keeps it consistent with other pointers i.e trbe_write, trbe_limit. > > That is a fair point. Please add a comment to explain your design choice and > make sure the sparse checker is happy with all of it.
Added a comment.
> >> >> Snippet from $cat drivers/hwtracing/coresight/coresight-trbe.c | grep "trbe_base" >> There are just two places type casting trbe_base back to (void *). >> >> memset((void *)buf->trbe_base + head, ETE_IGNORE_PACKET, len); >> return buf->trbe_base + offset; >> WARN_ON(buf->trbe_write < buf->trbe_base); >> set_trbe_base_pointer(buf->trbe_base); >> buf->trbe_base = (unsigned long)vmap(pglist, nr_pages, VM_MAP, PAGE_KERNEL); >> if (IS_ERR((void *)buf->trbe_base)) { >> return ERR_PTR(buf->trbe_base); >> buf->trbe_limit = buf->trbe_base + nr_pages * PAGE_SIZE; >> buf->trbe_write = buf->trbe_base; >> vunmap((void *)buf->trbe_base); >> base = get_trbe_base_pointer(); >> buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf); >> if (buf->trbe_limit == buf->trbe_base) { >> buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf); >> if (buf->trbe_limit == buf->trbe_base) { >> offset = get_trbe_limit_pointer() - get_trbe_base_pointer(); >> buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf); >> if (buf->trbe_limit == buf->trbe_base) { >> WARN_ON(buf->trbe_base != get_trbe_base_pointer()); >> if (get_trbe_write_pointer() == get_trbe_base_pointer()) >> >>> casting? And IS_ERR() doesn't work with vmap(). >> >> Sure, will drop IS_ERR() here. >> > > [...] > > >>> >>>> + >>>> +static ssize_t dbm_show(struct device *dev, struct device_attribute *attr, char *buf) >>>> +{ >>>> + struct trbe_cpudata *cpudata = dev_get_drvdata(dev); >>>> + >>>> + return sprintf(buf, "%d\n", cpudata->trbe_dbm); >>>> +} >>>> +static DEVICE_ATTR_RO(dbm); >>> >>> What does "dbm" stand for? Looking at the documentation for TRBIDR_EL1.F, I >>> don't see what "dbm" relates to. >> >> I made it up to refer TRBIDR_EL1.F as "Dirty (and Access Flag) Bit Management". >> Could change it as "afdbm" to be more specific or if it is preferred. >> > > I don't see "afdbm" being a better solution - why not simply "flag"?
Replaced all reference for "dbm" with "flag".
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