diff options
| -rw-r--r-- | include/clk-uclass.h | 113 |
1 files changed, 103 insertions, 10 deletions
diff --git a/include/clk-uclass.h b/include/clk-uclass.h index 4353b664800..8c07e723cff 100644 --- a/include/clk-uclass.h +++ b/include/clk-uclass.h @@ -56,11 +56,20 @@ struct clk_ops { * default implementation, which assumes #clock-cells = <1>, and that * the DT cell contains a simple integer clock ID. * + * This function should be a simple translation of @args into @clock->id and + * (optionally) @clock->data. All other processing, allocation, or error + * checking should take place in request(). + * * At present, the clock API solely supports device-tree. If this * changes, other xxx_xlate() functions may be added to support those * other mechanisms. * - * Return: 0 if OK, or a negative error code. + * Return: + * * 0 on success + * * -%EINVAL if @args does not have the correct format. For example, it could + * have too many/few arguments. + * * -%ENOENT if @args has the correct format but cannot be translated. This can + * happen if translation involves a table lookup and @args is not present. */ int of_xlate(struct clk *clock, struct ofnode_phandle_args *args); @@ -75,16 +84,36 @@ int of_xlate(struct clk *clock, struct ofnode_phandle_args *args); * xxx_xlate() call, or as the only step in implementing a client's * clk_request() call. * - * Return: 0 if OK, or a negative error code. + * This is the right place to do bounds checking (rejecting invalid or + * unimplemented clocks), allocate resources, or perform other setup not done + * during driver probe(). Most clock drivers should allocate resources in their + * probe() function, but it is possible to lazily initialize something here. + * + * Return: + * * 0 on success + * * -%ENOENT, if there is no clock corresponding to @clock->id and + * @clock->data. */ int request(struct clk *clock); /** * round_rate() - Adjust a rate to the exact rate a clock can provide. - * @clk: The clock to manipulate. - * @rate: Desidered clock rate in Hz. + * @clk: The clock to query. + * @rate: Desired clock rate in Hz. * - * Return: rounded rate in Hz, or -ve error code. + * This function returns a new rate which can be provided to set_rate(). This + * new rate should be the closest rate to @rate which can be set without + * rounding. The following pseudo-code should hold:: + * + * for all rate in range(ULONG_MAX): + * rounded = round_rate(clk, rate) + * new_rate = set_rate(clk, rate) + * assert(IS_ERR_VALUE(new_rate) || new_rate == rounded) + * + * Return: + * * The rounded rate in Hz on success + * * A negative error value from another API (such as clk_get_rate()). This + * function must not return an error for any other reason. */ ulong round_rate(struct clk *clk, ulong rate); @@ -92,7 +121,22 @@ ulong round_rate(struct clk *clk, ulong rate); * get_rate() - Get current clock rate. * @clk: The clock to query. * - * Return: clock rate in Hz, or -ve error code + * This returns the current rate of a clock. If the clock is disabled, it + * returns the rate at which the clock would run if it was enabled. The + * following pseudo-code should hold:: + * + * disable(clk) + * rate = get_rate(clk) + * enable(clk) + * assert(get_rate(clk) == rate) + * + * Return: + * * The rate of @clk + * * -%ENOSYS if this function is not implemented for @clk + * * -%ENOENT if @clk->id is invalid. Prefer using an assert instead, and doing + * this check in request(). + * * Another negative error value (such as %EIO or %ECOMM) if the rate could + * not be determined due to a bus error. */ ulong get_rate(struct clk *clk); @@ -101,7 +145,27 @@ ulong get_rate(struct clk *clk); * @clk: The clock to manipulate. * @rate: New clock rate in Hz. * - * Return: new rate, or -ve error code. + * Set the rate of @clk to @rate. The actual rate may be rounded. However, + * excessive rounding should be avoided. It is left to the driver author's + * discretion when this function should attempt to round and when it should + * return an error. For example, a dividing clock might use the following + * pseudo-logic when implemening this function:: + * + * divisor = parent_rate / rate + * if divisor < min || divisor > max: + * return -EINVAL + * + * If there is any concern about rounding, prefer to let consumers make the + * decision by calling round_rate(). + * + * Return: + * * The new rate on success + * * -%ENOSYS if this function is not implemented for @clk + * * -%ENOENT if @clk->id is invalid. Prefer using an assert instead, and doing + * this check in request(). + * * -%EINVAL if @rate is not valid for @clk. + * * Another negative error value (such as %EIO or %ECOMM) if the rate could + * not be set due to a bus error. */ ulong set_rate(struct clk *clk, ulong rate); @@ -110,7 +174,19 @@ ulong set_rate(struct clk *clk, ulong rate); * @clk: The clock to manipulate. * @parent: New clock parent. * - * Return: zero on success, or -ve error code. + * Set the current parent of @clk to @parent. The rate of the clock may be + * modified by this call. If @clk was enabled before this function, it should + * remain enabled after this function, although it may be temporarily disabled + * if necessary. + * + * Return: + * * 0 on success + * * -%ENOSYS if this function is not implemented for @clk + * * -%ENOENT if @clk->id or @parent->id is invalid. Prefer using an assert + * instead, and doing this check in request(). + * * -%EINVAL if @parent is not a valid parent for @clk. + * * Another negative error value (such as %EIO or %ECOMM) if the parent could + * not be set due to a bus error. */ int set_parent(struct clk *clk, struct clk *parent); @@ -118,7 +194,16 @@ int set_parent(struct clk *clk, struct clk *parent); * enable() - Enable a clock. * @clk: The clock to manipulate. * - * Return: zero on success, or -ve error code. + * Enable (un-gate) the clock. This function should not modify the rate of the + * clock (see get_rate() for details). + * + * Return: + * * 0 on success + * * -%ENOSYS if this function is not implemented for @clk + * * -%ENOENT if @clk->id is invalid. Prefer using an assert instead, and doing + * this check in request(). + * * Another negative error value (such as %EIO or %ECOMM) if the clock could + * not be enabled due to a bus error. */ int enable(struct clk *clk); @@ -126,7 +211,15 @@ int enable(struct clk *clk); * disable() - Disable a clock. * @clk: The clock to manipulate. * - * Return: zero on success, or -ve error code. + * Disable (gate) the clock. This function should not modify the rate of the + * clock (see get_rate() for details). + * + * * 0 on success + * * -%ENOSYS if this function is not implemented for @clk + * * -%ENOENT if @clk->id is invalid. Prefer using an assert instead, and doing + * this check in request(). + * * Another negative error value (such as %EIO or %ECOMM) if the clock could + * not be disabled due to a bus error. */ int disable(struct clk *clk); |