[PATCH v3 0/2] fix dw-mmc-rockchip rk356x clock rates

[PATCH v3 0/2] fix dw-mmc-rockchip rk356x clock rates

[Peter Geis]

cc: Jaehoon Chung <jh80.chung@samsung.com>
cc: Ulf Hansson <ulf.hansson@linaro.org>
cc: Heiko Stuebner <heiko@sntech.de>
cc: linux-mmc@vger.kernel.org
cc: linux-arm-kernel@lists.infradead.org
cc: linux-rockchip@lists.infradead.org
cc: linux-kernel@vger.kernel.org

While lighting off support for the SoQuartz module, it was discoved the
dw-mmc-rockchip driver has tremendous log spam when the cd-broken flag
is enabled and no card is inserted.
The SoQuart requires the cd-broken flag as the CM4 module pinout it
follows has no card-detect pin.
These errors occur during card initialization on all rk356x chips, but
are amplified by cd-broken as the function is called multiple times each
poll cycle.

It was discovered the lowest possible clock rate the rk356x cru can
provide for the ciu clock in the default configuration is 750khz. There 
is an internal clock divider that makes the final minimum clock 375khz.
We could hardcode this, but it is possible it could change if the
default clock configuration changes.

To fix this, we must make two changes:
First, the dw-mmc core needs to be updated to allow a host driver to
save its requested minimum frequency. This is necessary as the mmc_host
struct isn't available when the host drivers initialization code is
called. The dw-mmc core can then apply the f_min later when the struct
is available.
Second, the dw-mmc-rockchip driver is extended to test the frequencies
mmc core will use during card initialization. It finds the lowest
supported frequency from the cru and saves it for later use by dw-mmc
core.


Changelog:
v3:
- add support in dw_mmc core for saving the minimum frequency (fixes
  setting f_min)
- add test for the lowest supported frequency to avoid clamping configs
  that don't have an error

v2:
- change from muting the error to attempting to fix the underlying issue
  by setting f_min in driver initialization

Peter Geis (2):
  mmc: host: dw_mmc: support setting f_min from host drivers
  mmc: host: dw-mmc-rockchip: fix handling invalid clock rates

 drivers/mmc/host/dw_mmc-rockchip.c | 27 +++++++++++++++++++++++----
 drivers/mmc/host/dw_mmc.c          |  7 ++++++-
 drivers/mmc/host/dw_mmc.h          |  2 ++
 3 files changed, 31 insertions(+), 5 deletions(-)

-- 
2.25.1


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[PATCH v3 2/2] mmc: host: dw-mmc-rockchip: fix handling invalid clock rates

[Peter Geis]

The Rockchip rk356x ciu clock cannot be set as low as the dw-mmc
hardware supports. This leads to a situation during card initialization
where the clock is set lower than the clock driver can support. The
dw-mmc-rockchip driver spews errors when this happens.
For normal operation this only happens a few times during boot, but when
cd-broken is enabled (in cases such as the SoQuartz module) this fires
multiple times each poll cycle.

Fix this by testing the lowest possible frequency that the clock driver
can support which is within the mmc specification. Divide that rate by
the internal divider and set f_min to this.

Signed-off-by: Peter Geis <pgwipeout@gmail.com>
---
 drivers/mmc/host/dw_mmc-rockchip.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/host/dw_mmc-rockchip.c b/drivers/mmc/host/dw_mmc-rockchip.c
index 95d0ec0f5f3a..f825487aa739 100644
--- a/drivers/mmc/host/dw_mmc-rockchip.c
+++ b/drivers/mmc/host/dw_mmc-rockchip.c
@@ -15,7 +15,9 @@
 #include "dw_mmc.h"
 #include "dw_mmc-pltfm.h"
 
-#define RK3288_CLKGEN_DIV       2
+#define RK3288_CLKGEN_DIV	2
+
+static const unsigned int freqs[] = { 100000, 200000, 300000, 400000 };
 
 struct dw_mci_rockchip_priv_data {
 	struct clk		*drv_clk;
@@ -51,7 +53,7 @@ static void dw_mci_rk3288_set_ios(struct dw_mci *host, struct mmc_ios *ios)
 
 	ret = clk_set_rate(host->ciu_clk, cclkin);
 	if (ret)
-		dev_warn(host->dev, "failed to set rate %uHz\n", ios->clock);
+		dev_warn(host->dev, "failed to set rate %uHz err: %d\n", cclkin, ret);
 
 	bus_hz = clk_get_rate(host->ciu_clk) / RK3288_CLKGEN_DIV;
 	if (bus_hz != host->bus_hz) {
@@ -290,13 +292,30 @@ static int dw_mci_rk3288_parse_dt(struct dw_mci *host)
 
 static int dw_mci_rockchip_init(struct dw_mci *host)
 {
+	int ret, i;
+
 	/* It is slot 8 on Rockchip SoCs */
 	host->sdio_id0 = 8;
 
-	if (of_device_is_compatible(host->dev->of_node,
-				    "rockchip,rk3288-dw-mshc"))
+	if (of_device_is_compatible(host->dev->of_node, "rockchip,rk3288-dw-mshc")) {
 		host->bus_hz /= RK3288_CLKGEN_DIV;
 
+		/* clock driver will fail if the clock is less than the lowest source clock
+		 * divided by the internal clock divider. Test for the lowest available
+		 * clock and set the minimum freq to clock / clock divider.
+		 */
+
+		for (i = 0; i < ARRAY_SIZE(freqs); i++) {
+			ret = clk_round_rate(host->ciu_clk, freqs[i] * RK3288_CLKGEN_DIV);
+			if (ret > 0) {
+				host->minimum_speed = ret / RK3288_CLKGEN_DIV;
+				break;
+			}
+		}
+		if (ret < 0)
+			dev_warn(host->dev, "no valid minimum freq: %d\n", ret);
+	}
+
 	return 0;
 }
 
-- 
2.25.1


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Re: [PATCH v3 2/2] mmc: host: dw-mmc-rockchip: fix handling invalid clock rates

[Ulf Hansson]

On Sat, 5 Mar 2022 at 22:58, Peter Geis <pgwipeout@gmail.com> wrote:
>
> The Rockchip rk356x ciu clock cannot be set as low as the dw-mmc
> hardware supports. This leads to a situation during card initialization
> where the clock is set lower than the clock driver can support. The
> dw-mmc-rockchip driver spews errors when this happens.
> For normal operation this only happens a few times during boot, but when
> cd-broken is enabled (in cases such as the SoQuartz module) this fires
> multiple times each poll cycle.
>
> Fix this by testing the lowest possible frequency that the clock driver
> can support which is within the mmc specification. Divide that rate by
> the internal divider and set f_min to this.
>
> Signed-off-by: Peter Geis <pgwipeout@gmail.com>

Applied for next, thanks!

Kind regards
Uffe


> ---
>  drivers/mmc/host/dw_mmc-rockchip.c | 27 +++++++++++++++++++++++----
>  1 file changed, 23 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mmc/host/dw_mmc-rockchip.c b/drivers/mmc/host/dw_mmc-rockchip.c
> index 95d0ec0f5f3a..f825487aa739 100644
> --- a/drivers/mmc/host/dw_mmc-rockchip.c
> +++ b/drivers/mmc/host/dw_mmc-rockchip.c
> @@ -15,7 +15,9 @@
>  #include "dw_mmc.h"
>  #include "dw_mmc-pltfm.h"
>
> -#define RK3288_CLKGEN_DIV       2
> +#define RK3288_CLKGEN_DIV      2
> +
> +static const unsigned int freqs[] = { 100000, 200000, 300000, 400000 };
>
>  struct dw_mci_rockchip_priv_data {
>         struct clk              *drv_clk;
> @@ -51,7 +53,7 @@ static void dw_mci_rk3288_set_ios(struct dw_mci *host, struct mmc_ios *ios)
>
>         ret = clk_set_rate(host->ciu_clk, cclkin);
>         if (ret)
> -               dev_warn(host->dev, "failed to set rate %uHz\n", ios->clock);
> +               dev_warn(host->dev, "failed to set rate %uHz err: %d\n", cclkin, ret);
>
>         bus_hz = clk_get_rate(host->ciu_clk) / RK3288_CLKGEN_DIV;
>         if (bus_hz != host->bus_hz) {
> @@ -290,13 +292,30 @@ static int dw_mci_rk3288_parse_dt(struct dw_mci *host)
>
>  static int dw_mci_rockchip_init(struct dw_mci *host)
>  {
> +       int ret, i;
> +
>         /* It is slot 8 on Rockchip SoCs */
>         host->sdio_id0 = 8;
>
> -       if (of_device_is_compatible(host->dev->of_node,
> -                                   "rockchip,rk3288-dw-mshc"))
> +       if (of_device_is_compatible(host->dev->of_node, "rockchip,rk3288-dw-mshc")) {
>                 host->bus_hz /= RK3288_CLKGEN_DIV;
>
> +               /* clock driver will fail if the clock is less than the lowest source clock
> +                * divided by the internal clock divider. Test for the lowest available
> +                * clock and set the minimum freq to clock / clock divider.
> +                */
> +
> +               for (i = 0; i < ARRAY_SIZE(freqs); i++) {
> +                       ret = clk_round_rate(host->ciu_clk, freqs[i] * RK3288_CLKGEN_DIV);
> +                       if (ret > 0) {
> +                               host->minimum_speed = ret / RK3288_CLKGEN_DIV;
> +                               break;
> +                       }
> +               }
> +               if (ret < 0)
> +                       dev_warn(host->dev, "no valid minimum freq: %d\n", ret);
> +       }
> +
>         return 0;
>  }
>
> --
> 2.25.1
>

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