On 2016/6/14 10:13, Doug Anderson wrote:
Shawn,
On Mon, Jun 13, 2016 at 5:59 PM, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote:
Even in the case that an SoC designer didn't put a value into
corecfg_baseclkfreq that matched register[15:8], it seems very likely
that the rate returned from the clk_get_rate() would match.
I guess what I'm saying is that, to me, it seems like my patch isn't
broken in any real systems. If we ever find a system that needs this
behavior in the future, we can add it. Until then, it seems like my
patch would be fine. Do you agree?
I agree. But from the code itself, we should still use
SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN to see if we could get
it from internal register in case of some platforms don't
provide the clk stuff.. Sounds sane? :)
Could we wait until there exists a SoC that needs to provide
baseclkfreq in its sdhci_arasan_soc_ctl_map table and that needs this
value copied from register[15:8]?
yes, I think the base clk got from clk framework shouldn't
make any difference with that from register[15:8] if implemented. And
we now decide how to get base clk in a certain variant driver which
menas we know that this variant would never implement register[15:8], so
it looks fine for your patch with only a nit that we should make sure
we toggle up the COMMON_CLK. I saw your v2.1 to deal with it, so I think
it's okay now to add
Reviewed-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
AKA:
A) If you have a SoC where clk_get_rate() is right and software needs
to set baseclkfreq manualy, then you should include "baseclkfreq" in
your sdhci_arasan_soc_ctl_map table. This is like rk3399. Note that
if _both_ clk_get_rate() and register[15:8] are right, that's fine.
We can still use clk_get_rate() since it will be exactly the same as
register[15:8].
B) If you have a SoC that doesn't even expose corecfg_baseclkfreq to
software control, just don't include "baseclkfreq" in your
sdhci_arasan_soc_ctl_map table. Easy. This is how my patch treats
anyone using the current "generic" bindings, but you could easily just
specify an offset of "-1" for baseclkfreq if you didn't want to use
the generic bindings but couldn't control baseclkfreq.
C) If you have a SoC that provides a valid value in register[15:8] and
clk_get_rate() is wrong and software is required to copy the value
from register[15:8] to baseclkfreq, technically we should fix
clk_get_rate() anyway. It's good when common clock framework provides
correct values. NOTE: It seems very unlikely to me that
register[15:8] would be right AND that software would be required to
copy this value to baseclkfreq, but I suppose there are some pretty
crazy hardware designs out there.
D) If you have a SoC that provides a valid value in register[15:8] and
clk_get_rate() is wrong and can't be fixed (REALLY?) and software is
required to copy the value from register[15:8] to baseclkfreq, we will
need to add new code. My assertion is that such a SoC doesn't exist
and is unlikely to ever exist, so I am hesitant to add extra code to
support this SoC.
With my patch, A) and B) are certainly handled. I think C) is
unlikely to exist, but if it did exist then I'd say we should fix
clk_get_rate(). I think D) is VERY unlikely to exist. If I'm shown
proof of D) existing, I'm happy to submit a patch for it. Until we
see proof of D)'s existence, I don't think we should clutter the code
with support for it.
-Doug
--
Best Regards
Shawn Lin
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