Re: [PATCH V2 1/2] mmc: sdhci-msm: Add support to store supported vdd-io voltages
From: Jeremy McNicoll
Date: Thu Mar 22 2018 - 04:04:26 EST
On 2018-03-19 5:32 AM, Vijay Viswanath wrote:
On 3/7/2018 9:42 PM, Doug Anderson wrote:
Hi,
On Tue, Mar 6, 2018 at 11:13 PM, Vijay Viswanath
<vviswana@xxxxxxxxxxxxxx> wrote:
Hi Dough, Jeremy,
On 3/3/2018 4:38 AM, Jeremy McNicoll wrote:
On 2018-03-02 10:23 AM, Doug Anderson wrote:
Hi,
On Sun, Feb 11, 2018 at 10:01 PM, Vijay Viswanath
<vviswana@xxxxxxxxxxxxxx> wrote:
During probe check whether the vdd-io regulator of sdhc platform
device
can support 1.8V and 3V and store this information as a capability of
platform device.
Signed-off-by: Vijay Viswanath <vviswana@xxxxxxxxxxxxxx>
---
ÂÂ drivers/mmc/host/sdhci-msm.c | 38
++++++++++++++++++++++++++++++++++++++
ÂÂ 1 file changed, 38 insertions(+)
diff --git a/drivers/mmc/host/sdhci-msm.c
b/drivers/mmc/host/sdhci-msm.c
index c283291..5c23e92 100644
--- a/drivers/mmc/host/sdhci-msm.c
+++ b/drivers/mmc/host/sdhci-msm.c
@@ -23,6 +23,7 @@
ÂÂ #include <linux/iopoll.h>
ÂÂ #include "sdhci-pltfm.h"
+#include <linux/regulator/consumer.h>
This is a strange sort order for this include file. Why is it after
the local include?
ÂÂ #define CORE_MCI_VERSIONÂÂÂÂÂÂÂÂÂÂÂÂÂÂ 0x50
ÂÂ #define CORE_VERSION_MAJOR_SHIFTÂÂÂÂÂÂ 28
@@ -81,6 +82,9 @@
ÂÂ #define CORE_HC_SELECT_IN_HS400ÂÂÂÂÂÂÂ (6 << 19)
ÂÂ #define CORE_HC_SELECT_IN_MASK (7 << 19)
+#define CORE_3_0V_SUPPORTÂÂÂÂÂ (1 << 25)
+#define CORE_1_8V_SUPPORTÂÂÂÂÂ (1 << 26)
+
Is there something magical about 25 and 26? This is a new caps field,
so I'd have expected 0 and 1.
Yes, these bits are the same corresponding to the capabilities in the
Capabilities Register (offset 0x40). The bit positions become
important when
capabilities register doesn't show support to some voltages, but we can
support those voltages. At that time, we will have to fake
capabilities. The
changes for those are currently not yet pushed up.
ÂÂ #define CORE_CSR_CDC_CTLR_CFG0ÂÂÂÂÂÂÂÂ 0x130
ÂÂ #define CORE_SW_TRIG_FULL_CALIBÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ BIT(16)
ÂÂ #define CORE_HW_AUTOCAL_ENAÂÂÂÂÂÂÂÂÂÂÂ BIT(17)
@@ -148,6 +152,7 @@ struct sdhci_msm_host {
ÂÂÂÂÂÂÂÂÂ u32 curr_io_level;
ÂÂÂÂÂÂÂÂÂ wait_queue_head_t pwr_irq_wait;
ÂÂÂÂÂÂÂÂÂ bool pwr_irq_flag;
+ÂÂÂÂÂÂ u32 caps_0;
ÂÂ };
ÂÂ static unsigned int msm_get_clock_rate_for_bus_mode(struct
sdhci_host
*host,
@@ -1313,6 +1318,35 @@ static void sdhci_msm_writeb(struct sdhci_host
*host, u8 val, int reg)
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ sdhci_msm_check_power_status(host, req_type);
ÂÂ }
+static int sdhci_msm_set_regulator_caps(struct sdhci_msm_host
*msm_host)
+{
+ÂÂÂÂÂÂ struct mmc_host *mmc = msm_host->mmc;
+ÂÂÂÂÂÂ struct regulator *supply = mmc->supply.vqmmc;
+ÂÂÂÂÂÂ int i, count;
+ÂÂÂÂÂÂ u32 caps = 0, vdd_uV;
+
+ÂÂÂÂÂÂ if (!IS_ERR(mmc->supply.vqmmc)) {
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ count = regulator_count_voltages(supply);
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ if (count < 0)
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return count;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ for (i = 0; i < count; i++) {
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ vdd_uV = regulator_list_voltage(supply, i);
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ if (vdd_uV <= 0)
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ continue;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ if (vdd_uV > 2700000)
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ caps |= CORE_3_0V_SUPPORT;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ if (vdd_uV < 1950000)
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ caps |= CORE_1_8V_SUPPORT;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ }
Shouldn't you be using regulator_is_supported_voltage() rather than
open coding? Also: I've never personally worked on a device where it
was used, but there is definitely a concept floating about of a
voltage level of 1.2V. Maybe should copy the ranges from
mmc_regulator_set_vqmmc()?
regulator_is_supported_voltage() checks for a range and it also uses
regulator_list_voltage() internally. regulator_list_voltage() is also an
exported API for use by drivers AFAIK. Please correct if it is not.
Sure, regulator_list_voltage() is valid to call. I'm not saying that
your code is wrong or violates abstractions, just that it's
essentially re-implementing regulator_is_supported_voltage() for very
little gain. Calling regulator_is_supported_voltage() is better
because:
1. In theory, it should generate less code. Sure, it might loop twice
with the current implementation of regulator_is_supported_voltage(),
but for a non-time-critical section like this smaller code is likely
better than faster code (decreases kernel size / uses up less cache
space, etc).
2. If regulator_is_supported_voltage() is ever improved to be more
efficient you'll get that improvement automatically. If someone
happened to source vqmmc from a PWM regulator, for instance, trying to
enumerate all voltages like this would be a disaster.
3. Code will be simpler to understand.
You can replace your whole loop with:
if (regulator_is_supported_voltage(mmc->supply.vqmmc, 1700000, 1950000))
ÂÂ caps |= CORE_1_8V_SUPPORT
if (regulator_is_supported_voltage(mmc->supply.vqmmc, 2700000, 3600000))
ÂÂ caps |= CORE_3_0V_SUPPORT
Also: seems like you should have some way to deal with "caps" ending
up w/ no bits set. IIRC you can have a regulator that can be enabled
/ disabled but doesn't list a voltage, so if someone messed up their
device tree you could end up in this case. Should you print a
warning? ...or treat it as if we support "3.0V"? ...or ? I guess it
depends on how do you want patch #2 to behave in that case.
Both, initialize it to sane value and print something. This way at
least you have a good chance of booting and not hard hanging and you
are given a reasonable message indicating what needs to be fixed.
-jeremy
Its good to add a warning, but initializing it to some value might not
be appropriate. It will be better to leave it blank and if caps doesn't
have any of 1.8V/3V, better to not enable IO_PAD_PWR_SWITCH_EN.
That makes sense, this way if someone messes up their dts they will at
least get a message and we won't set the voltage to something that could
potentially destroy / harm the hardware.
-jeremy
+ÂÂÂÂÂÂ }
How should things behave if vqmmc is an error? In that case is it
important to not set "CORE_IO_PAD_PWR_SWITCH_EN" in patch set #2?
...or should you set "CORE_IO_PAD_PWR_SWITCH_EN" but then make sure
you don't set "CORE_IO_PAD_PWR_SWITCH"?
Thanks for the suggestion. If the regulators exit and doesn't list the
voltages, then I believe initialization itself will not happen. We
will not
have any available ocr and in sdhci_setup_host it should fail.
But these enhancements can be incorporated. Since this patch is already
acknowledged, I will incorporate these changes in a subsequent patch.
It's already acknowledged? I saw that your RFC was acknowledged by
Adrian Hunter but then you didn't include that tag in the posting of
v2, so I assumed for some reason it no longer applied. If you're
thinking that Ulf would be the one to apply this patch, he probably
doesn't know that it's Acked either.
Perhaps Adrian or Ulf can give direction for how they see this patch
proceeding.
Since I put up V2 anyway, I will include your suggestions and put V3. My
mistake, I didn't notice the ACK was for RFC.
+ÂÂÂÂÂÂ msm_host->caps_0 |= caps;
+ÂÂÂÂÂÂ pr_debug("%s: %s: supported caps: 0x%08x\n",
mmc_hostname(mmc),
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ __func__, caps);
+
+ÂÂÂÂÂÂ return 0;
+}
+
+
ÂÂ static const struct of_device_id sdhci_msm_dt_match[] = {
ÂÂÂÂÂÂÂÂÂ { .compatible = "qcom,sdhci-msm-v4" },
ÂÂÂÂÂÂÂÂÂ {},
@@ -1530,6 +1564,10 @@ static int sdhci_msm_probe(struct
platform_device
*pdev)
ÂÂÂÂÂÂÂÂÂ ret = sdhci_add_host(host);
ÂÂÂÂÂÂÂÂÂ if (ret)
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ goto pm_runtime_disable;
+ÂÂÂÂÂÂ ret = sdhci_msm_set_regulator_caps(msm_host);
+ÂÂÂÂÂÂ if (ret)
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ dev_err(&pdev->dev, "%s: Failed to set regulator
caps:
%d\n",
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ __func__, ret);
Why do you need __func__ here? You're already using dev_err(), that
gives an idea of where we are.
dev_err() doesn't give information of where it is getting called.
It gives you the driver and the error message should be unique to the
driver and easy to find. Including "__func__ in messages like this is
discouraged unless you are in a context where you somehow can't get
access to the device pointer. I suppose ultimately it's up the the
maintainer for individual cases but overall I've seen this to be a
consistently applied rule in the kernel.
In any case, why would this particular print be special that it should
include __func__ but all others (in this file, or in dev_err in
general) shouldn't?
ÂÂÂÂÂÂÂÂÂ pm_runtime_mark_last_busy(&pdev->dev);
ÂÂÂÂÂÂÂÂÂ pm_runtime_put_autosuspend(&pdev->dev);
--
ÂÂ Qualcomm India Private Limited, on behalf of Qualcomm Innovation
Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
Linux Foundation Collaborative Project.
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Thanks,
Vijay
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Thanks,
Vijay
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