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SubjectRe: [PATCH v2 6/9] scsi: ufs: qcom: Expose the reset controller for PHY
On Fri, Feb 1, 2019 at 9:56 AM Stephen Boyd <swboyd@chromium.org> wrote:
>
> Quoting Evan Green (2019-01-23 14:11:34)
> > Expose a reset controller that the phy can use to perform its
> > initialization in a single callback.
> >
> > Also, change the use of the phy functions from ufs-qcom such that
> > phy_poweron actually fires up the phy, and phy_poweroff actually
> > powers it down.
>
> This looks like two patches. One introduces a reset controller and the
> other changes the phy functions somehow. Can this be split up and then
> the commit text for the second half to change the phy functions can
> explain a little more of the theory behind how it's OK to change the
> code flow that way?

Sure, I can split the change in two.

>
> >
> > Signed-off-by: Evan Green <evgreen@chromium.org>
> >
> > ---
> > Note: This change depends on the remaining changes in this series,
> > since UFS PHY reset now needs to be done by the PHY driver.
>
> What does it depend on? Is there a bisection hole introduced here? An by
> bisection hole I mean more than the problem that an older DT is used
> with this new code.

Everything still builds, but there is a functional bisection hole here
in that UFS won't come up if you have this change but not the
following changes. The problem is that this change removes the reset
assert/deassert from ufs-qcom, and it's not until the next change that
the PHY is taught to use the reset controller to do those required
resets. Technically it's "phy: qcom-qmp: Utilize UFS reset controller"
that does the needed reset assert/deassert for qmp-phy, and "phy:
qcom-ufs: Refactor all init steps into phy_poweron" for the older
phy-qcom-ufs.

I was trying to keep changes in different components separate. Let me
refactor it into a way that makes more sense from a functional
perspective. The downside is that a couple of changes will touch three
drivers (both PHYs and the UFS controller) in a single change. But the
upside is that it's probably easier to review, and there will be no
bisection hole.

>
> >
> > Changes in v2:
> > - Remove include of reset.h (Stephen)
>
> Usually we include headers in both the C file and the header files that
> use structs from header files. It wouldn't hurt to include
> reset-controller.h in the ufs-qcom.c file. For one thing, it would help
> a grep find reset controller drivers trim based on files ending in .c
> instead of having to figure out which C file includes the .h file where
> the reset-controller header is included.

Sure, will do.

>
> > - Fix error print of phy_power_on (Stephen)
> > - Comment for reset controller warnings on id != 0 (Stephen)
> > - Add static to ufs_qcom_reset_ops (Stephen).
> >
> > drivers/scsi/ufs/Kconfig | 1 +
> > drivers/scsi/ufs/ufs-qcom.c | 111 ++++++++++++++++++++++--------------
> > drivers/scsi/ufs/ufs-qcom.h | 4 ++
> > 3 files changed, 72 insertions(+), 44 deletions(-)
> >
> > diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
> > index 3aeadb14aae1e..277ed6ad71c9b 100644
> > --- a/drivers/scsi/ufs/ufs-qcom.c
> > +++ b/drivers/scsi/ufs/ufs-qcom.c
> > @@ -255,11 +260,6 @@ static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
> > if (is_rate_B)
> > phy_set_mode(phy, PHY_MODE_UFS_HS_B);
> >
> > - /* Assert PHY reset and apply PHY calibration values */
> > - ufs_qcom_assert_reset(hba);
> > - /* provide 1ms delay to let the reset pulse propagate */
> > - usleep_range(1000, 1100);
> > -
> > /* phy initialization - calibrate the phy */
> > ret = phy_init(phy);
> > if (ret) {
> > @@ -268,15 +268,6 @@ static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
> > goto out;
> > }
> >
> > - /* De-assert PHY reset and start serdes */
> > - ufs_qcom_deassert_reset(hba);
> > -
> > - /*
> > - * after reset deassertion, phy will need all ref clocks,
> > - * voltage, current to settle down before starting serdes.
> > - */
> > - usleep_range(1000, 1100);
> > -
> > /* power on phy - start serdes and phy's power and clocks */
> > ret = phy_power_on(phy);
> > if (ret) {
> > @@ -290,7 +281,6 @@ static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
> > return 0;
> >
> > out_disable_phy:
> > - ufs_qcom_assert_reset(hba);
> > phy_exit(phy);
> > out:
> > return ret;
> > @@ -554,21 +544,10 @@ static int ufs_qcom_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
> > ufs_qcom_disable_lane_clks(host);
> > phy_power_off(phy);
> >
> > - /* Assert PHY soft reset */
> > - ufs_qcom_assert_reset(hba);
> > - goto out;
> > - }
> > -
> > - /*
> > - * If UniPro link is not active, PHY ref_clk, main PHY analog power
> > - * rail and low noise analog power rail for PLL can be switched off.
> > - */
> > - if (!ufs_qcom_is_link_active(hba)) {
> > + } else if (!ufs_qcom_is_link_active(hba)) {
> > ufs_qcom_disable_lane_clks(host);
> > - phy_power_off(phy);
> > }
> >
> > -out:
> > return ret;
> > }
> >
> > @@ -578,21 +557,26 @@ static int ufs_qcom_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
> > struct phy *phy = host->generic_phy;
> > int err;
> >
> > - err = phy_power_on(phy);
> > - if (err) {
> > - dev_err(hba->dev, "%s: failed enabling regs, err = %d\n",
> > - __func__, err);
> > - goto out;
> > - }
> > + if (ufs_qcom_is_link_off(hba)) {
> > + err = phy_power_on(phy);
> > + if (err) {
> > + dev_err(hba->dev, "%s: failed PHY power on: %d\n",
> > + __func__, err);
> > + return err;
> > + }
> >
> > - err = ufs_qcom_enable_lane_clks(host);
> > - if (err)
> > - goto out;
> > + err = ufs_qcom_enable_lane_clks(host);
> > + if (err)
> > + return err;
> >
> > - hba->is_sys_suspended = false;
> > + } else if (!ufs_qcom_is_link_active(hba)) {
> > + err = ufs_qcom_enable_lane_clks(host);
> > + if (err)
> > + return err;
> > + }
> >
> > -out:
> > - return err;
> > + hba->is_sys_suspended = false;
> > + return 0;
> > }
> >
> > struct ufs_qcom_dev_params {
> > @@ -1118,8 +1102,6 @@ static int ufs_qcom_setup_clocks(struct ufs_hba *hba, bool on,
> > return 0;
> >
> > if (on && (status == POST_CHANGE)) {
> > - phy_power_on(host->generic_phy);
> > -
> > /* enable the device ref clock for HS mode*/
> > if (ufshcd_is_hs_mode(&hba->pwr_info))
> > ufs_qcom_dev_ref_clk_ctrl(host, true);
> > @@ -1131,9 +1113,6 @@ static int ufs_qcom_setup_clocks(struct ufs_hba *hba, bool on,
> > if (!ufs_qcom_is_link_active(hba)) {
> > /* disable device ref_clk */
> > ufs_qcom_dev_ref_clk_ctrl(host, false);
> > -
> > - /* powering off PHY during aggressive clk gating */
> > - phy_power_off(host->generic_phy);
> > }
> >
> > vote = host->bus_vote.min_bw_vote;
>
> All the above hunks should probably be another patch with a motivation
> and explanation about what's going on in the commit text.

Ok.

>
> > @@ -1147,6 +1126,41 @@ static int ufs_qcom_setup_clocks(struct ufs_hba *hba, bool on,
> > return err;
> > }
> >
> > +static int
> > +ufs_qcom_reset_assert(struct reset_controller_dev *rcdev, unsigned long id)
> > +{
> > + struct ufs_qcom_host *host = rcdev_to_ufs_host(rcdev);
> > +
> > + /* Currently this code only knows about a single reset. */
>
> Ultra nitpick: Drop the full stop to be consistent with single line
> comment style in this function?

Ok. Maybe I'll add the period to the other comment in this function,
so that the two functions are consistent with each other.

>
> > + WARN_ON(id);
> > + ufs_qcom_assert_reset(host->hba);
> > + /* provide 1ms delay to let the reset pulse propagate */
> > + usleep_range(1000, 1100);
> > + return 0;
> > +}
> > +
> > +static int
> > +ufs_qcom_reset_deassert(struct reset_controller_dev *rcdev, unsigned long id)
> > +{
> > + struct ufs_qcom_host *host = rcdev_to_ufs_host(rcdev);
> > +
> > + /* Currently this code only knows about a single reset. */
>
> Well now it's different!

Not anymore!

>
> > + WARN_ON(id);
> > + ufs_qcom_deassert_reset(host->hba);
> > +
> > + /*
> > + * after reset deassertion, phy will need all ref clocks,
> > + * voltage, current to settle down before starting serdes.
> > + */
> > + usleep_range(1000, 1100);
> > + return 0;
> > +}
> > +
> > +const static struct reset_control_ops ufs_qcom_reset_ops = {
>
> const goes after static. Funny, there are some other grep hits for
> 'const static' in the kernel, but it's a small minority. Maybe those
> should be fixed.

Ok. Apparently there are historical reasons why nearly all compilers
accept any order of these two classes of keywords. Which means I never
remember what the right way is :)

>
> > + .assert = ufs_qcom_reset_assert,
> > + .deassert = ufs_qcom_reset_deassert,
> > +};
> > +
> > #define ANDROID_BOOT_DEV_MAX 30
> > static char android_boot_dev[ANDROID_BOOT_DEV_MAX];
> >
>
> Ooh Android!
>
> > @@ -1191,6 +1205,15 @@ static int ufs_qcom_init(struct ufs_hba *hba)
> > host->hba = hba;
> > ufshcd_set_variant(hba, host);
> >
> > + /* Fire up the reset controller. Failure here is non-fatal. */
> > + host->rcdev.of_node = dev->of_node;
> > + host->rcdev.ops = &ufs_qcom_reset_ops;
> > + host->rcdev.owner = dev->driver->owner;
> > + host->rcdev.nr_resets = 1;
> > + err = devm_reset_controller_register(dev, &host->rcdev);
> > + if (err)
> > + dev_warn(dev, "Failed to register reset controller\n");
>
> reset err to 0 because we don't care to fail here (it's just a warn, not
> a dev_err)?

Sure.

>
> > +
> > /*
> > * voting/devoting device ref_clk source is time consuming hence
> > * skip devoting it during aggressive clock gating. This clock

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