* Re: [PATCH v4 2/2] mmc: sdhci-msm: Actually set the actual clock
2020-12-11 17:12 ` [PATCH v4 2/2] mmc: sdhci-msm: Actually set the actual clock Douglas Anderson
@ 2020-12-14 12:43 ` Veerabhadrarao Badiganti
2020-12-14 17:22 ` Doug Anderson
2020-12-14 16:42 ` Bjorn Andersson
1 sibling, 1 reply; 5+ messages in thread
From: Veerabhadrarao Badiganti @ 2020-12-14 12:43 UTC (permalink / raw)
To: Douglas Anderson, Ulf Hansson, Adrian Hunter
Cc: Stephen Boyd, Taniya Das, Andy Gross, Bjorn Andersson,
linux-arm-msm, linux-kernel, linux-mmc
On 12/11/2020 10:42 PM, Douglas Anderson wrote:
> The MSM SDHCI driver always set the "actual_clock" field to 0. It had
> a comment about it not being needed because we weren't using the
> standard SDHCI divider mechanism and we'd just fallback to
> "host->clock". However, it's still better to provide the actual
> clock. Why?
>
> 1. It will make timeout calculations slightly better. On one system I
> have, the eMMC requets 200 MHz (for HS400-ES) but actually gets 192
> MHz. These are close, but why not get the more accurate one.
>
> 2. If things are seriously off in the clock driver and it's missing
> rates or picking the wrong rate (maybe it's rounding up instead of
> down), this will make it much more obvious what's going on.
>
> NOTE: we have to be a little careful here because the "actual_clock"
> field shouldn't include the multiplier that sdhci-msm needs
> internally.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
>
> Changes in v4:
> - ("mmc: sdhci-msm: Actually set the actual clock") new for v4.
>
> drivers/mmc/host/sdhci-msm.c | 32 ++++++++++++++------------------
> 1 file changed, 14 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index 50beb407dbe9..08a3960001ad 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -328,7 +328,7 @@ static void sdhci_msm_v5_variant_writel_relaxed(u32 val,
> writel_relaxed(val, host->ioaddr + offset);
> }
>
> -static unsigned int msm_get_clock_rate_for_bus_mode(struct sdhci_host *host,
> +static unsigned int msm_get_clock_mult_for_bus_mode(struct sdhci_host *host,
> unsigned int clock)
nit: clock variable not being used anymore. We can drop it.
> {
> struct mmc_ios ios = host->mmc->ios;
> @@ -342,8 +342,8 @@ static unsigned int msm_get_clock_rate_for_bus_mode(struct sdhci_host *host,
> ios.timing == MMC_TIMING_MMC_DDR52 ||
> ios.timing == MMC_TIMING_MMC_HS400 ||
> host->flags & SDHCI_HS400_TUNING)
> - clock *= 2;
> - return clock;
> + return 2;
> + return 1;
> }
>
> static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> @@ -354,14 +354,16 @@ static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> struct mmc_ios curr_ios = host->mmc->ios;
> struct clk *core_clk = msm_host->bulk_clks[0].clk;
> unsigned long achieved_rate;
> + unsigned int desired_rate;
> + unsigned int mult;
> int rc;
>
> - clock = msm_get_clock_rate_for_bus_mode(host, clock);
> - rc = dev_pm_opp_set_rate(mmc_dev(host->mmc), clock);
> + mult = msm_get_clock_mult_for_bus_mode(host, clock);
> + desired_rate = clock * mult;
> + rc = dev_pm_opp_set_rate(mmc_dev(host->mmc), desired_rate);
> if (rc) {
> pr_err("%s: Failed to set clock at rate %u at timing %d\n",
> - mmc_hostname(host->mmc), clock,
> - curr_ios.timing);
> + mmc_hostname(host->mmc), desired_rate, curr_ios.timing);
> return;
> }
>
> @@ -371,11 +373,12 @@ static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> * encounter it.
> */
> achieved_rate = clk_get_rate(core_clk);
> - if (achieved_rate > clock)
> + if (achieved_rate > desired_rate)
> pr_warn("%s: Card appears overclocked; req %u Hz, actual %lu Hz\n",
> - mmc_hostname(host->mmc), clock, achieved_rate);
> + mmc_hostname(host->mmc), desired_rate, achieved_rate);
> + host->mmc->actual_clock = achieved_rate / mult;
>
> - msm_host->clk_rate = clock;
> + msm_host->clk_rate = desired_rate;
Can you set msm_host->clk_rate also to achieved_rate?
At few places in this driver, host->clock is being used where
achieved_rate should be used ideally.
I will replace those instances with 'msm_host->clk_rate' in a separate
patch once this change merged.
> pr_debug("%s: Setting clock at rate %lu at timing %d\n",
> mmc_hostname(host->mmc), achieved_rate, curr_ios.timing);
> }
> @@ -1756,13 +1759,6 @@ static unsigned int sdhci_msm_get_min_clock(struct sdhci_host *host)
> static void __sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
> {
> u16 clk;
> - /*
> - * Keep actual_clock as zero -
> - * - since there is no divider used so no need of having actual_clock.
> - * - MSM controller uses SDCLK for data timeout calculation. If
> - * actual_clock is zero, host->clock is taken for calculation.
> - */
> - host->mmc->actual_clock = 0;
>
> sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
>
> @@ -1785,7 +1781,7 @@ static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
> struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
>
> if (!clock) {
> - msm_host->clk_rate = clock;
> + host->mmc->actual_clock = msm_host->clk_rate = 0;
> goto out;
> }
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v4 2/2] mmc: sdhci-msm: Actually set the actual clock
2020-12-14 12:43 ` Veerabhadrarao Badiganti
@ 2020-12-14 17:22 ` Doug Anderson
0 siblings, 0 replies; 5+ messages in thread
From: Doug Anderson @ 2020-12-14 17:22 UTC (permalink / raw)
To: Veerabhadrarao Badiganti
Cc: Ulf Hansson, Adrian Hunter, Stephen Boyd, Taniya Das, Andy Gross,
Bjorn Andersson, linux-arm-msm, LKML, Linux MMC List
Hi,
On Mon, Dec 14, 2020 at 4:44 AM Veerabhadrarao Badiganti
<vbadigan@codeaurora.org> wrote:
>
>
> On 12/11/2020 10:42 PM, Douglas Anderson wrote:
> > The MSM SDHCI driver always set the "actual_clock" field to 0. It had
> > a comment about it not being needed because we weren't using the
> > standard SDHCI divider mechanism and we'd just fallback to
> > "host->clock". However, it's still better to provide the actual
> > clock. Why?
> >
> > 1. It will make timeout calculations slightly better. On one system I
> > have, the eMMC requets 200 MHz (for HS400-ES) but actually gets 192
> > MHz. These are close, but why not get the more accurate one.
> >
> > 2. If things are seriously off in the clock driver and it's missing
> > rates or picking the wrong rate (maybe it's rounding up instead of
> > down), this will make it much more obvious what's going on.
> >
> > NOTE: we have to be a little careful here because the "actual_clock"
> > field shouldn't include the multiplier that sdhci-msm needs
> > internally.
> >
> > Signed-off-by: Douglas Anderson <dianders@chromium.org>
> > ---
> >
> > Changes in v4:
> > - ("mmc: sdhci-msm: Actually set the actual clock") new for v4.
> >
> > drivers/mmc/host/sdhci-msm.c | 32 ++++++++++++++------------------
> > 1 file changed, 14 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> > index 50beb407dbe9..08a3960001ad 100644
> > --- a/drivers/mmc/host/sdhci-msm.c
> > +++ b/drivers/mmc/host/sdhci-msm.c
> > @@ -328,7 +328,7 @@ static void sdhci_msm_v5_variant_writel_relaxed(u32 val,
> > writel_relaxed(val, host->ioaddr + offset);
> > }
> >
> > -static unsigned int msm_get_clock_rate_for_bus_mode(struct sdhci_host *host,
> > +static unsigned int msm_get_clock_mult_for_bus_mode(struct sdhci_host *host,
> > unsigned int clock)
>
> nit: clock variable not being used anymore. We can drop it.
Good point. Sending out a v5 with this.
> > {
> > struct mmc_ios ios = host->mmc->ios;
> > @@ -342,8 +342,8 @@ static unsigned int msm_get_clock_rate_for_bus_mode(struct sdhci_host *host,
> > ios.timing == MMC_TIMING_MMC_DDR52 ||
> > ios.timing == MMC_TIMING_MMC_HS400 ||
> > host->flags & SDHCI_HS400_TUNING)
> > - clock *= 2;
> > - return clock;
> > + return 2;
> > + return 1;
> > }
> >
> > static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> > @@ -354,14 +354,16 @@ static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> > struct mmc_ios curr_ios = host->mmc->ios;
> > struct clk *core_clk = msm_host->bulk_clks[0].clk;
> > unsigned long achieved_rate;
> > + unsigned int desired_rate;
> > + unsigned int mult;
> > int rc;
> >
> > - clock = msm_get_clock_rate_for_bus_mode(host, clock);
> > - rc = dev_pm_opp_set_rate(mmc_dev(host->mmc), clock);
> > + mult = msm_get_clock_mult_for_bus_mode(host, clock);
> > + desired_rate = clock * mult;
> > + rc = dev_pm_opp_set_rate(mmc_dev(host->mmc), desired_rate);
> > if (rc) {
> > pr_err("%s: Failed to set clock at rate %u at timing %d\n",
> > - mmc_hostname(host->mmc), clock,
> > - curr_ios.timing);
> > + mmc_hostname(host->mmc), desired_rate, curr_ios.timing);
> > return;
> > }
> >
> > @@ -371,11 +373,12 @@ static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> > * encounter it.
> > */
> > achieved_rate = clk_get_rate(core_clk);
> > - if (achieved_rate > clock)
> > + if (achieved_rate > desired_rate)
> > pr_warn("%s: Card appears overclocked; req %u Hz, actual %lu Hz\n",
> > - mmc_hostname(host->mmc), clock, achieved_rate);
> > + mmc_hostname(host->mmc), desired_rate, achieved_rate);
> > + host->mmc->actual_clock = achieved_rate / mult;
> >
> > - msm_host->clk_rate = clock;
> > + msm_host->clk_rate = desired_rate;
>
>
> Can you set msm_host->clk_rate also to achieved_rate?
Personally I'd rather not, but if you are sure that's what you want I
won't object to it too strongly. Why do I feel this way? The member
"clk_rate" contains the value that we passed to dev_pm_opp_set_rate()
the first time and I'd rather use that exact same value in
sdhci_msm_runtime_resume(). Mostly I'm just being paranoid in case
there is a bug and the operations aren't "stable".
For instance, let's imagine a fictional case where somewhere in the
clock framework there is a transition to kHz (something like this
_actually_ happens in the DRM subsystem):
clk_set_rate(rate_hz):
rate_khz = rate_hz / 1000;
real_clk_set_rate(rate_khz);
real_clk_set_rate(rate_khz)
rate_hz = rate_khz * 1000;
for each table_rate in table:
if table_rate <= rate_hz:
break;
set_hw_rate(table_rate);
real_clk_get_rate()
rate_hz = get_hw_rate();
return rate_hz / 1000;
clk_get_rate()
rate_khz = real_clk_get_rate()
return rate_khz * 1000;
Now if your table has these rates:
{ 111111111, 222222222, 333333333 }
Calling clk_set_rate(400000000) will set your rate to 333333333 Hz.
Now calling clk_get_rate() will return you 333333000. Now calling
clk_set_rate(333333000) will set your rate to 222222222 Hz!
IMO the above would be a bug, but I have seen things like that happen.
It's safer to stash the actual rate that we _requested_ and, if we
need to request the rate again, we pass that same value. That should
always work. I added a comment to at least make it look more explicit
that we're stashing the requested value.
> At few places in this driver, host->clock is being used where
> achieved_rate should be used ideally.
> I will replace those instances with 'msm_host->clk_rate' in a separate
> patch once this change merged.
Sounds good, thanks!
-Doug
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v4 2/2] mmc: sdhci-msm: Actually set the actual clock
2020-12-11 17:12 ` [PATCH v4 2/2] mmc: sdhci-msm: Actually set the actual clock Douglas Anderson
2020-12-14 12:43 ` Veerabhadrarao Badiganti
@ 2020-12-14 16:42 ` Bjorn Andersson
1 sibling, 0 replies; 5+ messages in thread
From: Bjorn Andersson @ 2020-12-14 16:42 UTC (permalink / raw)
To: Douglas Anderson
Cc: Ulf Hansson, Adrian Hunter, Stephen Boyd, Taniya Das, vbadigan,
Andy Gross, linux-arm-msm, linux-kernel, linux-mmc
On Fri 11 Dec 11:12 CST 2020, Douglas Anderson wrote:
> The MSM SDHCI driver always set the "actual_clock" field to 0. It had
> a comment about it not being needed because we weren't using the
> standard SDHCI divider mechanism and we'd just fallback to
> "host->clock". However, it's still better to provide the actual
> clock. Why?
>
> 1. It will make timeout calculations slightly better. On one system I
> have, the eMMC requets 200 MHz (for HS400-ES) but actually gets 192
> MHz. These are close, but why not get the more accurate one.
>
> 2. If things are seriously off in the clock driver and it's missing
> rates or picking the wrong rate (maybe it's rounding up instead of
> down), this will make it much more obvious what's going on.
>
> NOTE: we have to be a little careful here because the "actual_clock"
> field shouldn't include the multiplier that sdhci-msm needs
> internally.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Regards,
Bjorn
> ---
>
> Changes in v4:
> - ("mmc: sdhci-msm: Actually set the actual clock") new for v4.
>
> drivers/mmc/host/sdhci-msm.c | 32 ++++++++++++++------------------
> 1 file changed, 14 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index 50beb407dbe9..08a3960001ad 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -328,7 +328,7 @@ static void sdhci_msm_v5_variant_writel_relaxed(u32 val,
> writel_relaxed(val, host->ioaddr + offset);
> }
>
> -static unsigned int msm_get_clock_rate_for_bus_mode(struct sdhci_host *host,
> +static unsigned int msm_get_clock_mult_for_bus_mode(struct sdhci_host *host,
> unsigned int clock)
> {
> struct mmc_ios ios = host->mmc->ios;
> @@ -342,8 +342,8 @@ static unsigned int msm_get_clock_rate_for_bus_mode(struct sdhci_host *host,
> ios.timing == MMC_TIMING_MMC_DDR52 ||
> ios.timing == MMC_TIMING_MMC_HS400 ||
> host->flags & SDHCI_HS400_TUNING)
> - clock *= 2;
> - return clock;
> + return 2;
> + return 1;
> }
>
> static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> @@ -354,14 +354,16 @@ static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> struct mmc_ios curr_ios = host->mmc->ios;
> struct clk *core_clk = msm_host->bulk_clks[0].clk;
> unsigned long achieved_rate;
> + unsigned int desired_rate;
> + unsigned int mult;
> int rc;
>
> - clock = msm_get_clock_rate_for_bus_mode(host, clock);
> - rc = dev_pm_opp_set_rate(mmc_dev(host->mmc), clock);
> + mult = msm_get_clock_mult_for_bus_mode(host, clock);
> + desired_rate = clock * mult;
> + rc = dev_pm_opp_set_rate(mmc_dev(host->mmc), desired_rate);
> if (rc) {
> pr_err("%s: Failed to set clock at rate %u at timing %d\n",
> - mmc_hostname(host->mmc), clock,
> - curr_ios.timing);
> + mmc_hostname(host->mmc), desired_rate, curr_ios.timing);
> return;
> }
>
> @@ -371,11 +373,12 @@ static void msm_set_clock_rate_for_bus_mode(struct sdhci_host *host,
> * encounter it.
> */
> achieved_rate = clk_get_rate(core_clk);
> - if (achieved_rate > clock)
> + if (achieved_rate > desired_rate)
> pr_warn("%s: Card appears overclocked; req %u Hz, actual %lu Hz\n",
> - mmc_hostname(host->mmc), clock, achieved_rate);
> + mmc_hostname(host->mmc), desired_rate, achieved_rate);
> + host->mmc->actual_clock = achieved_rate / mult;
>
> - msm_host->clk_rate = clock;
> + msm_host->clk_rate = desired_rate;
> pr_debug("%s: Setting clock at rate %lu at timing %d\n",
> mmc_hostname(host->mmc), achieved_rate, curr_ios.timing);
> }
> @@ -1756,13 +1759,6 @@ static unsigned int sdhci_msm_get_min_clock(struct sdhci_host *host)
> static void __sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
> {
> u16 clk;
> - /*
> - * Keep actual_clock as zero -
> - * - since there is no divider used so no need of having actual_clock.
> - * - MSM controller uses SDCLK for data timeout calculation. If
> - * actual_clock is zero, host->clock is taken for calculation.
> - */
> - host->mmc->actual_clock = 0;
>
> sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
>
> @@ -1785,7 +1781,7 @@ static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
> struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
>
> if (!clock) {
> - msm_host->clk_rate = clock;
> + host->mmc->actual_clock = msm_host->clk_rate = 0;
> goto out;
> }
>
> --
> 2.29.2.576.ga3fc446d84-goog
>
^ permalink raw reply [flat|nested] 5+ messages in thread