Hi Sean, On Sun, 27 Feb 2022 at 12:38, Sean Anderson <sean...@gmail.com> wrote: > > On 2/26/22 1:36 PM, Simon Glass wrote: > > Hi Sean, > > > > On Tue, 1 Feb 2022 at 21:24, Sean Anderson <sean...@gmail.com> wrote: > >> > >> On 2/1/22 10:59 PM, Simon Glass wrote: > >>> Hi Sean, > >>> > >>> On Tue, 1 Feb 2022 at 07:49, Sean Anderson <sean...@gmail.com> wrote: > >>>> > >>>> On 1/27/22 4:35 PM, Simon Glass wrote: > >>>>> Hi Sean, > >>>>> > >>>>> On Thu, 27 Jan 2022 at 08:43, Sean Anderson <sean...@gmail.com> wrote: > >>>>>> > >>>>>> On 1/27/22 10:05 AM, Simon Glass wrote: > >>>>>>> Hi Sean, > >>>>>>> > >>>>>>> On Sat, 15 Jan 2022 at 15:25, Sean Anderson <sean...@gmail.com> wrote: > >>>>>>>> > >>>>>>>> When freeing a clock there is not much we can do if there is an > >>>>>>>> error, and > >>>>>>>> most callers do not actually check the return value. Even e.g. > >>>>>>>> checking to > >>>>>>>> make sure that clk->id is valid should have been done in request() > >>>>>>>> in the > >>>>>>>> first place (unless someone is messing with the driver behind our > >>>>>>>> back). > >>>>>>>> Just return void and don't bother returning an error. > >>>>>>>> > >>>>>>>> Signed-off-by: Sean Anderson <sean...@gmail.com> > >>>>>>>> --- > >>>>>>>> > >>>>>>>> drivers/clk/clk-uclass.c | 7 +++---- > >>>>>>>> drivers/clk/clk_sandbox.c | 6 +++--- > >>>>>>>> include/clk-uclass.h | 8 +++----- > >>>>>>>> 3 files changed, 9 insertions(+), 12 deletions(-) > >>>>>>>> > >>>>>>> > >>>>>>> We have the same thing in other places too, but I am a little worried > >>>>>>> about removing error checking. We try to avoid checking arguments too > >>>>>>> much in U-Boot, due to code-size concerns, so I suppose I agree that > >>>>>>> an invalid clk should be caught by a debug assertion rather than a > >>>>>>> full check. But with driver model we have generally added an error > >>>>>>> return to every uclass method, for consistency and to permit returning > >>>>>>> error information if needed. > >>>>>>> > >>>>>>> Regards, > >>>>>>> Simon > >>>>>>> > >>>>>> > >>>>>> So there are a few reasons why I don't think a return value is useful > >>>>>> here. To illustrate this, consider a typical user of the clock API: > >>>>>> > >>>>>> struct clk a, b; > >>>>>> > >>>>>> ret = clk_get_by_name(dev, "a", &a); > >>>>>> if (ret) > >>>>>> return ret; > >>>>>> > >>>>>> ret = clk_get_by_name(dev, "b", &b); > >>>>>> if (ret) > >>>>>> goto free_a; > >>>>>> > >>>>>> ret = clk_set_rate(&a, 5000000); > >>>>>> if (ret) > >>>>>> goto free_b; > >>>>>> > >>>>>> ret = clk_enable(&b); > >>>>>> > >>>>>> free_b: > >>>>>> clk_free(&b); > >>>>>> free_a: > >>>>>> clk_free(&a); > >>>>>> return ret; > >>>>>> > >>>>>> - Because a and b are "thick pointers" they do not need any cleanup to > >>>>>> free their own resources. The only cleanup might be if the clock > >>>>>> driver has allocated something in clk_request (more on this > >>>>>> below) > >>>>>> - By the time we call clk_free, the mutable portions of the function > >>>>>> have already completed. In effect, the function has succeeded, > >>>>>> regardless of whether clk_free fails. Additionally, we cannot > >>>>>> take any > >>>>>> action if it fails, since we still have to free both clocks. > >>>>>> - clk_free occurs during the error path of the function. Even if it > >>>>>> errored, we do not want to override the existing error from one > >>>>>> of the > >>>>>> functions doing "real" work. > >>>>>> > >>>>>> The last thing is that no clock driver actually does anything in rfree. > >>>>>> The only driver with this function is the sandbox driver. I would like > >>>>>> to remove the function altogether. As I understand it, the existing API > >>>>>> is inspired by the reset drivers, so I would like to review its usage > >>>>>> in > >>>>>> the reset subsystem before removing it for the clock subsystem. I also > >>>>>> want to make some changes to how rates and enables/disables are > >>>>>> calculated which might provide a case for rfree. But once that is > >>>>>> complete I think there will be no users still. > >>>>> > >>>>> What does this all look like in Linux? > >>>> > >>>> Their equivalent (clk_put) returns void, and generally so do most other > >>>> cleanup functions, since .device_remove also returns void. > >>> > >>> We really cannot ignore errors from device_remove(). > >> > >> Once you are at device_remove, all the users are gone and it's up to the > >> device to clean up after itself. And often there is nothing we can do > >> once remove is called. As you yourself say in device_remove, > >> > >> /* We can't put the children back */ > > > > Well this assumes that device_remove() is actually removing the > > device, not just disabling DMA, etc. > > > >> > >> Really the only sensible thing is to print an error and continue booting > >> if possible. > >> > >> And of course no clock drivers actually use this function anyway, nor do > >> (all but 5) users check it. > >> > >>> Anyway I think what you say about the 'thick pointer' makes sense. But > >>> my expectation was that removing a clock might turn off a clock above > >>> it in the tree, for example. > >> > >> No, this just frees resources (as is documented). If you want to turn > >> off a clock, you have to call clk_disable. In fact, a very common use > >> case is just like the example above, where the consmer frees the clock > >> after enabling it. > >> > >> (This is also why clk->enable_count/rate are basically useless for > >> anything other than CCF clocks) > > > > How about a clock provided by an audio codec on an I2C bus? Should > > clk_free() do anything in that case? I assume not. I think the > > compelling part of your argument is that it is a 'think pointer' and > > disable does nothing. So can you update clk_rfree() etc. to document > > what is allowed to be done in that function? > > The ideal case would be if you wanted to allocate some per-struct-clk > data. Then, the correct place to free it would be rfree. But no one > does this, and if they did it would probably be better to free things > in remove. > > Actually... no one in clk, reset, or power-domain does anything with > rfree. So I am inclined to just remove it altogether.
Well, I suppose it is easy enough to add later, if needed. What does Linux use this for? > > --Sean > > > Reviewed-by: Simon Glass <s...@chromium.org> > Regards, SImon