* [PATCH 1/2] soc: qcom: geni: Don't ignore clk_round_rate() errors in geni_se_clk_tbl_get()
@ 2018-08-30 18:36 Douglas Anderson
2018-08-30 18:36 ` [PATCH 2/2] soc: qcom: geni: geni_se_clk_freq_match() should always accept multiples Douglas Anderson
2018-09-05 23:37 ` [PATCH 1/2] soc: qcom: geni: Don't ignore clk_round_rate() errors in geni_se_clk_tbl_get() Matthias Kaehlcke
0 siblings, 2 replies; 6+ messages in thread
From: Douglas Anderson @ 2018-08-30 18:36 UTC (permalink / raw)
To: Andy Gross, Bjorn Andersson
Cc: mka, girishm, dkota, evgreen, swboyd, Douglas Anderson,
linux-arm-msm, linux-soc, David Brown, linux-kernel
The function clk_round_rate() is defined to return a "long", not an
"unsigned long". That's because it might return a negative error
code. Change the call in geni_se_clk_tbl_get() to check for errors.
NOTE: overall the idea that we should iterate over clk_round_rate() to
try to reconstruct a table already present in the clock driver is
questionable. Specifically:
- This method relies on "clk_round_rate()" rounding up.
- This method only works if the table is sorted and has no duplicates.
...this patch doesn't try to fix those problems, it just makes the
error handling more correct.
Fixes: eddac5af0654 ("soc: qcom: Add GENI based QUP Wrapper driver")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
drivers/soc/qcom/qcom-geni-se.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/soc/qcom/qcom-geni-se.c b/drivers/soc/qcom/qcom-geni-se.c
index feed3db21c10..1b19b8428c4a 100644
--- a/drivers/soc/qcom/qcom-geni-se.c
+++ b/drivers/soc/qcom/qcom-geni-se.c
@@ -513,7 +513,7 @@ EXPORT_SYMBOL(geni_se_resources_on);
*/
int geni_se_clk_tbl_get(struct geni_se *se, unsigned long **tbl)
{
- unsigned long freq = 0;
+ long freq = 0;
int i;
if (se->clk_perf_tbl) {
@@ -529,7 +529,7 @@ int geni_se_clk_tbl_get(struct geni_se *se, unsigned long **tbl)
for (i = 0; i < MAX_CLK_PERF_LEVEL; i++) {
freq = clk_round_rate(se->clk, freq + 1);
- if (!freq || freq == se->clk_perf_tbl[i - 1])
+ if (freq <= 0 || freq == se->clk_perf_tbl[i - 1])
break;
se->clk_perf_tbl[i] = freq;
}
--
2.19.0.rc0.228.g281dcd1b4d0-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 2/2] soc: qcom: geni: geni_se_clk_freq_match() should always accept multiples
2018-08-30 18:36 [PATCH 1/2] soc: qcom: geni: Don't ignore clk_round_rate() errors in geni_se_clk_tbl_get() Douglas Anderson
@ 2018-08-30 18:36 ` Douglas Anderson
2018-09-06 0:20 ` Matthias Kaehlcke
2018-09-05 23:37 ` [PATCH 1/2] soc: qcom: geni: Don't ignore clk_round_rate() errors in geni_se_clk_tbl_get() Matthias Kaehlcke
1 sibling, 1 reply; 6+ messages in thread
From: Douglas Anderson @ 2018-08-30 18:36 UTC (permalink / raw)
To: Andy Gross, Bjorn Andersson
Cc: mka, girishm, dkota, evgreen, swboyd, Douglas Anderson,
linux-arm-msm, linux-soc, David Brown, linux-kernel
The geni_se_clk_freq_match() has some strange semantics. Specifically
it is defined with two modes:
1. It can find a clock that's an exact multiple of the requested rate
2. If can find a non-exact match but it can't handle multiples then
...but callers should always be able to handle a clock that is a
multiple of the requested clock so mode #2 doesn't really make sense.
Let's change the semantics so that the non-exact match can also accept
multiples and then change the code to handle that.
The only caller of this code is the unlanded SPI driver [1] which
currently passes "exact = True", thus it should be safe to change the
semantics in this way. ...and, in fact, the SPI driver should likely
be modified to pass "exact = False" (with the new semantics) since
that will allow it to work with SPI devices that request a clock rate
that doesn't exactly match a rate we can make.
[1] https://lkml.kernel.org/r/1535107336-2214-1-git-send-email-dkota@codeaurora.org
Fixes: eddac5af0654 ("soc: qcom: Add GENI based QUP Wrapper driver")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
drivers/soc/qcom/qcom-geni-se.c | 37 ++++++++++++++++++++-------------
1 file changed, 22 insertions(+), 15 deletions(-)
diff --git a/drivers/soc/qcom/qcom-geni-se.c b/drivers/soc/qcom/qcom-geni-se.c
index 1b19b8428c4a..092b32a315c3 100644
--- a/drivers/soc/qcom/qcom-geni-se.c
+++ b/drivers/soc/qcom/qcom-geni-se.c
@@ -544,16 +544,17 @@ EXPORT_SYMBOL(geni_se_clk_tbl_get);
* @se: Pointer to the concerned serial engine.
* @req_freq: Requested clock frequency.
* @index: Index of the resultant frequency in the table.
- * @res_freq: Resultant frequency which matches or is closer to the
- * requested frequency.
+ * @res_freq: Resultant frequency of the source clock.
* @exact: Flag to indicate exact multiple requirement of the requested
* frequency.
*
- * This function is called by the protocol drivers to determine the matching
- * or exact multiple of the requested frequency, as provided by the serial
- * engine clock in order to meet the performance requirements. If there is
- * no matching or exact multiple of the requested frequency found, then it
- * selects the closest floor frequency, if exact flag is not set.
+ * This function is called by the protocol drivers to determine the best match
+ * of the requested frequency as provided by the serial engine clock in order
+ * to meet the performance requirements.
+ *
+ * If we return success:
+ * - if @exact is true then @res_freq / <an_integer> == @req_freq
+ * - if @exact is false then @res_freq / <an_integer> <= @req_freq
*
* Return: 0 on success, standard Linux error codes on failure.
*/
@@ -564,6 +565,9 @@ int geni_se_clk_freq_match(struct geni_se *se, unsigned long req_freq,
unsigned long *tbl;
int num_clk_levels;
int i;
+ unsigned long best_delta;
+ unsigned long new_delta;
+ unsigned int divider;
num_clk_levels = geni_se_clk_tbl_get(se, &tbl);
if (num_clk_levels < 0)
@@ -572,18 +576,21 @@ int geni_se_clk_freq_match(struct geni_se *se, unsigned long req_freq,
if (num_clk_levels == 0)
return -EINVAL;
- *res_freq = 0;
+ best_delta = 0;
for (i = 0; i < num_clk_levels; i++) {
- if (!(tbl[i] % req_freq)) {
+ divider = DIV_ROUND_UP(tbl[i], req_freq);
+ new_delta = req_freq - tbl[i] / divider;
+ if (!best_delta || new_delta < best_delta) {
+ /* We have a new best! */
*index = i;
*res_freq = tbl[i];
- return 0;
- }
- if (!(*res_freq) || ((tbl[i] > *res_freq) &&
- (tbl[i] < req_freq))) {
- *index = i;
- *res_freq = tbl[i];
+ /* If the new best is exact then we're done */
+ if (new_delta == 0)
+ return 0;
+
+ /* Record how close we got */
+ best_delta = new_delta;
}
}
--
2.19.0.rc0.228.g281dcd1b4d0-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] soc: qcom: geni: Don't ignore clk_round_rate() errors in geni_se_clk_tbl_get()
2018-08-30 18:36 [PATCH 1/2] soc: qcom: geni: Don't ignore clk_round_rate() errors in geni_se_clk_tbl_get() Douglas Anderson
2018-08-30 18:36 ` [PATCH 2/2] soc: qcom: geni: geni_se_clk_freq_match() should always accept multiples Douglas Anderson
@ 2018-09-05 23:37 ` Matthias Kaehlcke
2018-09-06 16:33 ` Doug Anderson
1 sibling, 1 reply; 6+ messages in thread
From: Matthias Kaehlcke @ 2018-09-05 23:37 UTC (permalink / raw)
To: Douglas Anderson
Cc: Andy Gross, Bjorn Andersson, girishm, dkota, evgreen, swboyd,
linux-arm-msm, linux-soc, David Brown, linux-kernel
On Thu, Aug 30, 2018 at 11:36:11AM -0700, Douglas Anderson wrote:
> The function clk_round_rate() is defined to return a "long", not an
> "unsigned long". That's because it might return a negative error
> code. Change the call in geni_se_clk_tbl_get() to check for errors.
>
> NOTE: overall the idea that we should iterate over clk_round_rate() to
> try to reconstruct a table already present in the clock driver is
> questionable. Specifically:
> - This method relies on "clk_round_rate()" rounding up.
> - This method only works if the table is sorted and has no duplicates.
> ...this patch doesn't try to fix those problems, it just makes the
> error handling more correct.
>
> Fixes: eddac5af0654 ("soc: qcom: Add GENI based QUP Wrapper driver")
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
>
> drivers/soc/qcom/qcom-geni-se.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/soc/qcom/qcom-geni-se.c b/drivers/soc/qcom/qcom-geni-se.c
> index feed3db21c10..1b19b8428c4a 100644
> --- a/drivers/soc/qcom/qcom-geni-se.c
> +++ b/drivers/soc/qcom/qcom-geni-se.c
> @@ -513,7 +513,7 @@ EXPORT_SYMBOL(geni_se_resources_on);
> */
> int geni_se_clk_tbl_get(struct geni_se *se, unsigned long **tbl)
> {
> - unsigned long freq = 0;
> + long freq = 0;
nit: Since you are already touching this you could also remove the
pointless initialization, 'freq' is always assigned before it is used.
> int i;
>
> if (se->clk_perf_tbl) {
> @@ -529,7 +529,7 @@ int geni_se_clk_tbl_get(struct geni_se *se, unsigned long **tbl)
>
> for (i = 0; i < MAX_CLK_PERF_LEVEL; i++) {
> freq = clk_round_rate(se->clk, freq + 1);
> - if (!freq || freq == se->clk_perf_tbl[i - 1])
> + if (freq <= 0 || freq == se->clk_perf_tbl[i - 1])
> break;
> se->clk_perf_tbl[i] = freq;
> }
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2] soc: qcom: geni: geni_se_clk_freq_match() should always accept multiples
2018-08-30 18:36 ` [PATCH 2/2] soc: qcom: geni: geni_se_clk_freq_match() should always accept multiples Douglas Anderson
@ 2018-09-06 0:20 ` Matthias Kaehlcke
2018-09-06 16:33 ` Doug Anderson
0 siblings, 1 reply; 6+ messages in thread
From: Matthias Kaehlcke @ 2018-09-06 0:20 UTC (permalink / raw)
To: Douglas Anderson
Cc: Andy Gross, Bjorn Andersson, girishm, dkota, evgreen, swboyd,
linux-arm-msm, linux-soc, David Brown, linux-kernel
On Thu, Aug 30, 2018 at 11:36:12AM -0700, Douglas Anderson wrote:
> The geni_se_clk_freq_match() has some strange semantics. Specifically
> it is defined with two modes:
> 1. It can find a clock that's an exact multiple of the requested rate
> 2. If can find a non-exact match but it can't handle multiples then
nit: s/If/It/
>
> ...but callers should always be able to handle a clock that is a
> multiple of the requested clock so mode #2 doesn't really make sense.
> Let's change the semantics so that the non-exact match can also accept
> multiples and then change the code to handle that.
>
> The only caller of this code is the unlanded SPI driver [1] which
> currently passes "exact = True", thus it should be safe to change the
> semantics in this way. ...and, in fact, the SPI driver should likely
> be modified to pass "exact = False" (with the new semantics) since
> that will allow it to work with SPI devices that request a clock rate
> that doesn't exactly match a rate we can make.
>
> [1] https://lkml.kernel.org/r/1535107336-2214-1-git-send-email-dkota@codeaurora.org
>
> Fixes: eddac5af0654 ("soc: qcom: Add GENI based QUP Wrapper driver")
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
>
> drivers/soc/qcom/qcom-geni-se.c | 37 ++++++++++++++++++++-------------
> 1 file changed, 22 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/soc/qcom/qcom-geni-se.c b/drivers/soc/qcom/qcom-geni-se.c
> index 1b19b8428c4a..092b32a315c3 100644
> --- a/drivers/soc/qcom/qcom-geni-se.c
> +++ b/drivers/soc/qcom/qcom-geni-se.c
> @@ -544,16 +544,17 @@ EXPORT_SYMBOL(geni_se_clk_tbl_get);
> * @se: Pointer to the concerned serial engine.
> * @req_freq: Requested clock frequency.
> * @index: Index of the resultant frequency in the table.
> - * @res_freq: Resultant frequency which matches or is closer to the
> - * requested frequency.
> + * @res_freq: Resultant frequency of the source clock.
> * @exact: Flag to indicate exact multiple requirement of the requested
> * frequency.
> *
> - * This function is called by the protocol drivers to determine the matching
> - * or exact multiple of the requested frequency, as provided by the serial
> - * engine clock in order to meet the performance requirements. If there is
> - * no matching or exact multiple of the requested frequency found, then it
> - * selects the closest floor frequency, if exact flag is not set.
> + * This function is called by the protocol drivers to determine the best match
> + * of the requested frequency as provided by the serial engine clock in order
> + * to meet the performance requirements.
> + *
> + * If we return success:
> + * - if @exact is true then @res_freq / <an_integer> == @req_freq
> + * - if @exact is false then @res_freq / <an_integer> <= @req_freq
> *
> * Return: 0 on success, standard Linux error codes on failure.
> */
> @@ -564,6 +565,9 @@ int geni_se_clk_freq_match(struct geni_se *se, unsigned long req_freq,
> unsigned long *tbl;
> int num_clk_levels;
> int i;
> + unsigned long best_delta;
> + unsigned long new_delta;
> + unsigned int divider;
>
> num_clk_levels = geni_se_clk_tbl_get(se, &tbl);
> if (num_clk_levels < 0)
> @@ -572,18 +576,21 @@ int geni_se_clk_freq_match(struct geni_se *se, unsigned long req_freq,
> if (num_clk_levels == 0)
> return -EINVAL;
>
> - *res_freq = 0;
> + best_delta = 0;
> for (i = 0; i < num_clk_levels; i++) {
> - if (!(tbl[i] % req_freq)) {
> + divider = DIV_ROUND_UP(tbl[i], req_freq);
> + new_delta = req_freq - tbl[i] / divider;
> + if (!best_delta || new_delta < best_delta) {
nit: if you assigned best_delta to ULONG_MAX above you could omit the
check for !best_delta here, better to read IMO.
> + /* We have a new best! */
> *index = i;
> *res_freq = tbl[i];
> - return 0;
> - }
>
> - if (!(*res_freq) || ((tbl[i] > *res_freq) &&
> - (tbl[i] < req_freq))) {
> - *index = i;
> - *res_freq = tbl[i];
> + /* If the new best is exact then we're done */
> + if (new_delta == 0)
> + return 0;
> +
> + /* Record how close we got */
> + best_delta = new_delta;
> }
> }
>
Looks good to me assuming that the statement "callers should always be
able to handle a clock that is a multiple of the requested clock" is
correct.
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2] soc: qcom: geni: geni_se_clk_freq_match() should always accept multiples
2018-09-06 0:20 ` Matthias Kaehlcke
@ 2018-09-06 16:33 ` Doug Anderson
0 siblings, 0 replies; 6+ messages in thread
From: Doug Anderson @ 2018-09-06 16:33 UTC (permalink / raw)
To: Matthias Kaehlcke
Cc: Andy Gross, Bjorn Andersson, Girish Mahadevan, Dilip Kota,
Evan Green, Stephen Boyd, linux-arm-msm,
open list:ARM/QUALCOMM SUPPORT, David Brown, LKML
Hi,
On Wed, Sep 5, 2018 at 5:20 PM, Matthias Kaehlcke <mka@chromium.org> wrote:
> On Thu, Aug 30, 2018 at 11:36:12AM -0700, Douglas Anderson wrote:
>> The geni_se_clk_freq_match() has some strange semantics. Specifically
>> it is defined with two modes:
>> 1. It can find a clock that's an exact multiple of the requested rate
>> 2. If can find a non-exact match but it can't handle multiples then
>
> nit: s/If/It/
Splleing was nvevr my strong suit. Done.
>> + best_delta = 0;
>> for (i = 0; i < num_clk_levels; i++) {
>> - if (!(tbl[i] % req_freq)) {
>> + divider = DIV_ROUND_UP(tbl[i], req_freq);
>> + new_delta = req_freq - tbl[i] / divider;
>> + if (!best_delta || new_delta < best_delta) {
>
> nit: if you assigned best_delta to ULONG_MAX above you could omit the
> check for !best_delta here, better to read IMO.
Done.
> Looks good to me assuming that the statement "callers should always be
> able to handle a clock that is a multiple of the requested clock" is
> correct.
I think we should be OK given that currently there's no real callers.
If we really need to add another parameter to disallow multiples we
can always do it later.
> Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Thanks for the reviews!
-Doug
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] soc: qcom: geni: Don't ignore clk_round_rate() errors in geni_se_clk_tbl_get()
2018-09-05 23:37 ` [PATCH 1/2] soc: qcom: geni: Don't ignore clk_round_rate() errors in geni_se_clk_tbl_get() Matthias Kaehlcke
@ 2018-09-06 16:33 ` Doug Anderson
0 siblings, 0 replies; 6+ messages in thread
From: Doug Anderson @ 2018-09-06 16:33 UTC (permalink / raw)
To: Matthias Kaehlcke
Cc: Andy Gross, Bjorn Andersson, Girish Mahadevan, Dilip Kota,
Evan Green, Stephen Boyd, linux-arm-msm,
open list:ARM/QUALCOMM SUPPORT, David Brown, LKML
Hi,
On Wed, Sep 5, 2018 at 4:37 PM, Matthias Kaehlcke <mka@chromium.org> wrote:
>> int geni_se_clk_tbl_get(struct geni_se *se, unsigned long **tbl)
>> {
>> - unsigned long freq = 0;
>> + long freq = 0;
>
> nit: Since you are already touching this you could also remove the
> pointless initialization, 'freq' is always assigned before it is used.
Done.
-Doug
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-09-06 16:33 UTC | newest]
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2018-08-30 18:36 [PATCH 1/2] soc: qcom: geni: Don't ignore clk_round_rate() errors in geni_se_clk_tbl_get() Douglas Anderson
2018-08-30 18:36 ` [PATCH 2/2] soc: qcom: geni: geni_se_clk_freq_match() should always accept multiples Douglas Anderson
2018-09-06 0:20 ` Matthias Kaehlcke
2018-09-06 16:33 ` Doug Anderson
2018-09-05 23:37 ` [PATCH 1/2] soc: qcom: geni: Don't ignore clk_round_rate() errors in geni_se_clk_tbl_get() Matthias Kaehlcke
2018-09-06 16:33 ` Doug Anderson
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