| Message ID | 1657560808-9795-1-git-send-email-quic_vnivarth@quicinc.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [V4] tty: serial: qcom-geni-serial: Fix get_clk_div_rate() which otherwise could return a sub-optimal clock rate. | expand |
Hi, On Mon, Jul 11, 2022 at 10:33 AM Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com> wrote: > > In the logic around call to clk_round_rate(), for some corner conditions, > get_clk_div_rate() could return an sub-optimal clock rate. Also, if an > exact clock rate was not found lowest clock was being returned. > > Search for suitable clock rate in 2 steps > a) exact match or within 2% tolerance > b) within 5% tolerance > This also takes care of corner conditions. > > Fixes: c2194bc999d4 ("tty: serial: qcom-geni-serial: Remove uart frequency table. Instead, find suitable frequency with call to clk_round_rate") > Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com> > --- > v4: replaced pr_dbg calls with dev_dbg > v3: simplified algorithm further, fixed robot compile warnings > v2: removed minor optimisations to make more readable > v1: intial patch contained slightly complicated logic > --- > drivers/tty/serial/qcom_geni_serial.c | 89 +++++++++++++++++++++-------------- > 1 file changed, 54 insertions(+), 35 deletions(-) > > diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c > index 2e23b65..f88b042 100644 > --- a/drivers/tty/serial/qcom_geni_serial.c > +++ b/drivers/tty/serial/qcom_geni_serial.c > @@ -943,52 +943,71 @@ static int qcom_geni_serial_startup(struct uart_port *uport) > return 0; > } > > -static unsigned long get_clk_div_rate(struct clk *clk, unsigned int baud, > - unsigned int sampling_rate, unsigned int *clk_div) > +static unsigned long find_clk_rate_in_tol(struct clk *clk, unsigned int desired_clk, > + unsigned int *clk_div, unsigned int percent_tol) > { > - unsigned long ser_clk; > - unsigned long desired_clk; > - unsigned long freq, prev; > + unsigned long freq; > unsigned long div, maxdiv; > - int64_t mult; > - > - desired_clk = baud * sampling_rate; > - if (!desired_clk) { > - pr_err("%s: Invalid frequency\n", __func__); > - return 0; > - } > + u64 mult; > + unsigned long offset, abs_tol, achieved; > > + abs_tol = div_u64((u64)desired_clk * percent_tol, 100); > maxdiv = CLK_DIV_MSK >> CLK_DIV_SHFT; > - prev = 0; > - > - for (div = 1; div <= maxdiv; div++) { > - mult = div * desired_clk; > - if (mult > ULONG_MAX) > + div = 1; > + while (div <= maxdiv) { > + mult = (u64)div * desired_clk; > + if (mult != (unsigned long)mult) > break; > > - freq = clk_round_rate(clk, (unsigned long)mult); > - if (!(freq % desired_clk)) { > - ser_clk = freq; > - break; > - } > + offset = div * abs_tol; > + freq = clk_round_rate(clk, mult - offset); > > - if (!prev) > - ser_clk = freq; > - else if (prev == freq) > + /* Can only get lower if we're done */ > + if (freq < mult - offset) > break; > > - prev = freq; > + /* > + * Re-calculate div in case rounding skipped rates but we > + * ended up at a good one, then check for a match. > + */ > + div = DIV_ROUND_CLOSEST(freq, desired_clk); > + achieved = DIV_ROUND_CLOSEST(freq, div); > + if (achieved <= desired_clk + abs_tol && > + achieved >= desired_clk - abs_tol) { > + *clk_div = div; > + return freq; > + } > + > + div = DIV_ROUND_UP(freq, desired_clk); > } > > - if (!ser_clk) { > - pr_err("%s: Can't find matching DFS entry for baud %d\n", > - __func__, baud); > - return ser_clk; > + return 0; > +} > + > +static unsigned long get_clk_div_rate(struct clk *clk, struct device *dev, > + unsigned int baud, unsigned int sampling_rate, unsigned int *clk_div) > +{ > + unsigned long ser_clk; > + unsigned long desired_clk; > + > + desired_clk = baud * sampling_rate; > + if (!desired_clk) { > + dev_dbg(dev, "Invalid frequency\n"); > + return 0; > } > > - *clk_div = ser_clk / desired_clk; > - if (!(*clk_div)) > - *clk_div = 1; > + /* > + * try to find a clock rate within 2% tolerance, then within > + */ > + ser_clk = find_clk_rate_in_tol(clk, desired_clk, clk_div, 2); > + if (!ser_clk) > + ser_clk = find_clk_rate_in_tol(clk, desired_clk, clk_div, 5); > + > + if (!ser_clk) > + dev_err(dev, "Couldn't find suitable clock rate for %d\n", desired_clk); > + else > + dev_dbg(dev, "desired_clk-%d, ser_clk-%d, clk_div-%d\n", > + desired_clk, ser_clk, *clk_div); Pretty sure the robot is going to yell at you again here. Here is my analysis in detail: desired_clk * type: unsigned long * proper format code: %lu * marginally acceptable code: %ld * format code you used in v3: %lu * did robot yell at you about this in v3: no * format code you used in v4: %d * will robot yell at you in v4: YES ser_clk: * type: unsigned long * proper format code: %lu * marginally acceptable code: %ld * format code you used in v3: %lu * did robot yell at you about this in v3: no * format code you used in v4: %d * will robot yell at you in v4: YES *clk_div: * type: unsigned int * proper format code: %u * marginally acceptable code: %d * format code you used in v3: %lu * did robot yell at you about this in v3: YES * format code you used in v4: %d * will robot yell at you in v4: no * should you change it to %u: yes -Doug
On 7/11/2022 11:35 PM, Doug Anderson wrote: > Hi, > > On Mon, Jul 11, 2022 at 10:33 AM Vijaya Krishna Nivarthi > <quic_vnivarth@quicinc.com> wrote: >> In the logic around call to clk_round_rate(), for some corner conditions, >> get_clk_div_rate() could return an sub-optimal clock rate. Also, if an >> exact clock rate was not found lowest clock was being returned. >> >> Search for suitable clock rate in 2 steps >> a) exact match or within 2% tolerance >> b) within 5% tolerance >> This also takes care of corner conditions. >> >> Fixes: c2194bc999d4 ("tty: serial: qcom-geni-serial: Remove uart frequency table. Instead, find suitable frequency with call to clk_round_rate") >> Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com> >> --- >> v4: replaced pr_dbg calls with dev_dbg >> v3: simplified algorithm further, fixed robot compile warnings >> v2: removed minor optimisations to make more readable >> v1: intial patch contained slightly complicated logic >> --- >> drivers/tty/serial/qcom_geni_serial.c | 89 +++++++++++++++++++++-------------- >> 1 file changed, 54 insertions(+), 35 deletions(-) >> >> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c >> index 2e23b65..f88b042 100644 >> --- a/drivers/tty/serial/qcom_geni_serial.c >> +++ b/drivers/tty/serial/qcom_geni_serial.c >> @@ -943,52 +943,71 @@ static int qcom_geni_serial_startup(struct uart_port *uport) >> return 0; >> } >> >> -static unsigned long get_clk_div_rate(struct clk *clk, unsigned int baud, >> - unsigned int sampling_rate, unsigned int *clk_div) >> +static unsigned long find_clk_rate_in_tol(struct clk *clk, unsigned int desired_clk, >> + unsigned int *clk_div, unsigned int percent_tol) >> { >> - unsigned long ser_clk; >> - unsigned long desired_clk; >> - unsigned long freq, prev; >> + unsigned long freq; >> unsigned long div, maxdiv; >> - int64_t mult; >> - >> - desired_clk = baud * sampling_rate; >> - if (!desired_clk) { >> - pr_err("%s: Invalid frequency\n", __func__); >> - return 0; >> - } >> + u64 mult; >> + unsigned long offset, abs_tol, achieved; >> >> + abs_tol = div_u64((u64)desired_clk * percent_tol, 100); >> maxdiv = CLK_DIV_MSK >> CLK_DIV_SHFT; >> - prev = 0; >> - >> - for (div = 1; div <= maxdiv; div++) { >> - mult = div * desired_clk; >> - if (mult > ULONG_MAX) >> + div = 1; >> + while (div <= maxdiv) { >> + mult = (u64)div * desired_clk; >> + if (mult != (unsigned long)mult) >> break; >> >> - freq = clk_round_rate(clk, (unsigned long)mult); >> - if (!(freq % desired_clk)) { >> - ser_clk = freq; >> - break; >> - } >> + offset = div * abs_tol; >> + freq = clk_round_rate(clk, mult - offset); >> >> - if (!prev) >> - ser_clk = freq; >> - else if (prev == freq) >> + /* Can only get lower if we're done */ >> + if (freq < mult - offset) >> break; >> >> - prev = freq; >> + /* >> + * Re-calculate div in case rounding skipped rates but we >> + * ended up at a good one, then check for a match. >> + */ >> + div = DIV_ROUND_CLOSEST(freq, desired_clk); >> + achieved = DIV_ROUND_CLOSEST(freq, div); >> + if (achieved <= desired_clk + abs_tol && >> + achieved >= desired_clk - abs_tol) { >> + *clk_div = div; >> + return freq; >> + } >> + >> + div = DIV_ROUND_UP(freq, desired_clk); >> } >> >> - if (!ser_clk) { >> - pr_err("%s: Can't find matching DFS entry for baud %d\n", >> - __func__, baud); >> - return ser_clk; >> + return 0; >> +} >> + >> +static unsigned long get_clk_div_rate(struct clk *clk, struct device *dev, >> + unsigned int baud, unsigned int sampling_rate, unsigned int *clk_div) >> +{ >> + unsigned long ser_clk; >> + unsigned long desired_clk; >> + >> + desired_clk = baud * sampling_rate; >> + if (!desired_clk) { >> + dev_dbg(dev, "Invalid frequency\n"); >> + return 0; >> } >> >> - *clk_div = ser_clk / desired_clk; >> - if (!(*clk_div)) >> - *clk_div = 1; >> + /* >> + * try to find a clock rate within 2% tolerance, then within >> + */ >> + ser_clk = find_clk_rate_in_tol(clk, desired_clk, clk_div, 2); >> + if (!ser_clk) >> + ser_clk = find_clk_rate_in_tol(clk, desired_clk, clk_div, 5); >> + >> + if (!ser_clk) >> + dev_err(dev, "Couldn't find suitable clock rate for %d\n", desired_clk); >> + else >> + dev_dbg(dev, "desired_clk-%d, ser_clk-%d, clk_div-%d\n", >> + desired_clk, ser_clk, *clk_div); > Pretty sure the robot is going to yell at you again here. Here is my > analysis in detail: > > desired_clk > * type: unsigned long > * proper format code: %lu > * marginally acceptable code: %ld > * format code you used in v3: %lu > * did robot yell at you about this in v3: no > * format code you used in v4: %d > * will robot yell at you in v4: YES > > ser_clk: > * type: unsigned long > * proper format code: %lu > * marginally acceptable code: %ld > * format code you used in v3: %lu > * did robot yell at you about this in v3: no > * format code you used in v4: %d > * will robot yell at you in v4: YES > > *clk_div: > * type: unsigned int > * proper format code: %u > * marginally acceptable code: %d > * format code you used in v3: %lu > * did robot yell at you about this in v3: YES > * format code you used in v4: %d > * will robot yell at you in v4: no > * should you change it to %u: yes > > > -Doug Thank you very much. For some reason robot seems to be more forgiving towards dev_funcs than pr_funcs, at least it did not yell at v4. Also I found usage of %d for uls at many locations. Made the changes and uploaded V5. -Vijay/
diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c index 2e23b65..f88b042 100644 --- a/drivers/tty/serial/qcom_geni_serial.c +++ b/drivers/tty/serial/qcom_geni_serial.c @@ -943,52 +943,71 @@ static int qcom_geni_serial_startup(struct uart_port *uport) return 0; } -static unsigned long get_clk_div_rate(struct clk *clk, unsigned int baud, - unsigned int sampling_rate, unsigned int *clk_div) +static unsigned long find_clk_rate_in_tol(struct clk *clk, unsigned int desired_clk, + unsigned int *clk_div, unsigned int percent_tol) { - unsigned long ser_clk; - unsigned long desired_clk; - unsigned long freq, prev; + unsigned long freq; unsigned long div, maxdiv; - int64_t mult; - - desired_clk = baud * sampling_rate; - if (!desired_clk) { - pr_err("%s: Invalid frequency\n", __func__); - return 0; - } + u64 mult; + unsigned long offset, abs_tol, achieved; + abs_tol = div_u64((u64)desired_clk * percent_tol, 100); maxdiv = CLK_DIV_MSK >> CLK_DIV_SHFT; - prev = 0; - - for (div = 1; div <= maxdiv; div++) { - mult = div * desired_clk; - if (mult > ULONG_MAX) + div = 1; + while (div <= maxdiv) { + mult = (u64)div * desired_clk; + if (mult != (unsigned long)mult) break; - freq = clk_round_rate(clk, (unsigned long)mult); - if (!(freq % desired_clk)) { - ser_clk = freq; - break; - } + offset = div * abs_tol; + freq = clk_round_rate(clk, mult - offset); - if (!prev) - ser_clk = freq; - else if (prev == freq) + /* Can only get lower if we're done */ + if (freq < mult - offset) break; - prev = freq; + /* + * Re-calculate div in case rounding skipped rates but we + * ended up at a good one, then check for a match. + */ + div = DIV_ROUND_CLOSEST(freq, desired_clk); + achieved = DIV_ROUND_CLOSEST(freq, div); + if (achieved <= desired_clk + abs_tol && + achieved >= desired_clk - abs_tol) { + *clk_div = div; + return freq; + } + + div = DIV_ROUND_UP(freq, desired_clk); } - if (!ser_clk) { - pr_err("%s: Can't find matching DFS entry for baud %d\n", - __func__, baud); - return ser_clk; + return 0; +} + +static unsigned long get_clk_div_rate(struct clk *clk, struct device *dev, + unsigned int baud, unsigned int sampling_rate, unsigned int *clk_div) +{ + unsigned long ser_clk; + unsigned long desired_clk; + + desired_clk = baud * sampling_rate; + if (!desired_clk) { + dev_dbg(dev, "Invalid frequency\n"); + return 0; } - *clk_div = ser_clk / desired_clk; - if (!(*clk_div)) - *clk_div = 1; + /* + * try to find a clock rate within 2% tolerance, then within + */ + ser_clk = find_clk_rate_in_tol(clk, desired_clk, clk_div, 2); + if (!ser_clk) + ser_clk = find_clk_rate_in_tol(clk, desired_clk, clk_div, 5); + + if (!ser_clk) + dev_err(dev, "Couldn't find suitable clock rate for %d\n", desired_clk); + else + dev_dbg(dev, "desired_clk-%d, ser_clk-%d, clk_div-%d\n", + desired_clk, ser_clk, *clk_div); return ser_clk; } @@ -1021,8 +1040,8 @@ static void qcom_geni_serial_set_termios(struct uart_port *uport, if (ver >= QUP_SE_VERSION_2_5) sampling_rate /= 2; - clk_rate = get_clk_div_rate(port->se.clk, baud, - sampling_rate, &clk_div); + clk_rate = get_clk_div_rate(port->se.clk, port->se.dev, baud, + sampling_rate, &clk_div); if (!clk_rate) goto out_restart_rx;
In the logic around call to clk_round_rate(), for some corner conditions, get_clk_div_rate() could return an sub-optimal clock rate. Also, if an exact clock rate was not found lowest clock was being returned. Search for suitable clock rate in 2 steps a) exact match or within 2% tolerance b) within 5% tolerance This also takes care of corner conditions. Fixes: c2194bc999d4 ("tty: serial: qcom-geni-serial: Remove uart frequency table. Instead, find suitable frequency with call to clk_round_rate") Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com> --- v4: replaced pr_dbg calls with dev_dbg v3: simplified algorithm further, fixed robot compile warnings v2: removed minor optimisations to make more readable v1: intial patch contained slightly complicated logic --- drivers/tty/serial/qcom_geni_serial.c | 89 +++++++++++++++++++++-------------- 1 file changed, 54 insertions(+), 35 deletions(-)