| Message ID | 1427730803-28635-2-git-send-email-javier.martinez@collabora.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Javier, 2015-03-31 0:53 GMT+09:00 Javier Martinez Canillas <javier.martinez@collabora.co.uk>: > The Samsung helpers functions to register clocks, add the clock instance > returned by the common clock framework to a lookup table that is used by > OF to lookup the clocks. > > But this table could also be useful to clock drivers if they need to get > a clock instance since the helper functions don't return them. > > The common clock framework __clk_lookup() function from the clk provider > API could be used by drivers as well. But it's more efficient to use the > Samsung specific lookup table that returns the clock instance in constant > time, than using the __clk_lookup() function that uses the clock name as > an index so it has a linear search time. Is this really something we should be concerned about? If so, maybe the generic look-up function should be rewritten to use something faster, such as tree or hash table? Best regards, Tomasz
Hello Tomasz, On 03/30/2015 06:02 PM, Tomasz Figa wrote: > Hi Javier, > > 2015-03-31 0:53 GMT+09:00 Javier Martinez Canillas > <javier.martinez@collabora.co.uk>: >> The Samsung helpers functions to register clocks, add the clock instance >> returned by the common clock framework to a lookup table that is used by >> OF to lookup the clocks. >> >> But this table could also be useful to clock drivers if they need to get >> a clock instance since the helper functions don't return them. >> >> The common clock framework __clk_lookup() function from the clk provider >> API could be used by drivers as well. But it's more efficient to use the >> Samsung specific lookup table that returns the clock instance in constant >> time, than using the __clk_lookup() function that uses the clock name as >> an index so it has a linear search time. > > Is this really something we should be concerned about? If so, maybe > the generic look-up function should be rewritten to use something > faster, such as tree or hash table? > I don't performance is a big issue here. I just thought that since the lookup table is already filled by the driver and the lookup function is one line, we could use that instead to get the performance benefit. But I don't mind to drop this patch and use the generic lookup function from the CCF API if that is preferred. > Best regards, > Tomasz > Best regards, Javier
Quoting Javier Martinez Canillas (2015-03-30 09:08:40) > Hello Tomasz, > > On 03/30/2015 06:02 PM, Tomasz Figa wrote: > > Hi Javier, > > > > 2015-03-31 0:53 GMT+09:00 Javier Martinez Canillas > > <javier.martinez@collabora.co.uk>: > >> The Samsung helpers functions to register clocks, add the clock instance > >> returned by the common clock framework to a lookup table that is used by > >> OF to lookup the clocks. > >> > >> But this table could also be useful to clock drivers if they need to get > >> a clock instance since the helper functions don't return them. > >> > >> The common clock framework __clk_lookup() function from the clk provider > >> API could be used by drivers as well. But it's more efficient to use the > >> Samsung specific lookup table that returns the clock instance in constant > >> time, than using the __clk_lookup() function that uses the clock name as > >> an index so it has a linear search time. > > > > Is this really something we should be concerned about? If so, maybe > > the generic look-up function should be rewritten to use something > > faster, such as tree or hash table? > > > > I don't performance is a big issue here. I just thought that since the > lookup table is already filled by the driver and the lookup function > is one line, we could use that instead to get the performance benefit. > > But I don't mind to drop this patch and use the generic lookup function > from the CCF API if that is preferred. Hello, I am not a fan of __clk_lookup and I don't like to see it used more and more outside of drivers/clk/clk.c. You mentioned that performance wasn't really the problem here. The real method for a driver to get a clock is with clk_get(). Any reason to not use that? Regards, Mike > > > Best regards, > > Tomasz > > > > Best regards, > Javier
diff --git a/drivers/clk/samsung/clk.c b/drivers/clk/samsung/clk.c index 9e1f88c04fd4..3b2868a70774 100644 --- a/drivers/clk/samsung/clk.c +++ b/drivers/clk/samsung/clk.c @@ -96,6 +96,12 @@ void samsung_clk_add_lookup(struct samsung_clk_provider *ctx, struct clk *clk, ctx->clk_data.clks[id] = clk; } +struct clk *samsung_clk_lookup(struct samsung_clk_provider *ctx, + unsigned int id) +{ + return ctx->clk_data.clks ? ctx->clk_data.clks[id] : NULL; +} + /* register a list of aliases */ void __init samsung_clk_register_alias(struct samsung_clk_provider *ctx, struct samsung_clock_alias *list, diff --git a/drivers/clk/samsung/clk.h b/drivers/clk/samsung/clk.h index e4c75383cea7..ad04220bd733 100644 --- a/drivers/clk/samsung/clk.h +++ b/drivers/clk/samsung/clk.h @@ -368,6 +368,9 @@ extern void __init samsung_clk_of_register_fixed_ext( extern void samsung_clk_add_lookup(struct samsung_clk_provider *ctx, struct clk *clk, unsigned int id); +extern struct clk *samsung_clk_lookup(struct samsung_clk_provider *ctx, + unsigned int id); + extern void samsung_clk_register_alias(struct samsung_clk_provider *ctx, struct samsung_clock_alias *list, unsigned int nr_clk);
The Samsung helpers functions to register clocks, add the clock instance returned by the common clock framework to a lookup table that is used by OF to lookup the clocks. But this table could also be useful to clock drivers if they need to get a clock instance since the helper functions don't return them. The common clock framework __clk_lookup() function from the clk provider API could be used by drivers as well. But it's more efficient to use the Samsung specific lookup table that returns the clock instance in constant time, than using the __clk_lookup() function that uses the clock name as an index so it has a linear search time. Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk> --- drivers/clk/samsung/clk.c | 6 ++++++ drivers/clk/samsung/clk.h | 3 +++ 2 files changed, 9 insertions(+)