phy: renesas: rcar-gen3-usb2: Avoid long delay in atomic context

The OTG PHY initialization sequence needs to wait for 20 ms at a specific
step, as described in commit 72c0339c115b ("phy: renesas:
rcar-gen3-usb2: follow the hardware manual procedure").

Commit 55a387ebb921 ("phy: renesas: rcar-gen3-usb2: Lock around hardware
registers and driver data") tried to address various problems in the
rcar-gen3-usb2 driver and converted the mutex protecting HW register
accesses to a spin lock, leaving, however, a long delay in the critical
section protected by the spin lock. This may become a problem,
especially on RT kernels.

To address this, release the spin lock before sleeping for 20 ms as
required by the HW manual and reacquire it afterwards. To avoid other
threads entering the critical section and configuring the HW while the
software is waiting for the OTG initialization to complete, introduce the
otg_initializing variable alongside the otg_init_done wait queue. Any
other thread trying to configure the HW while the OTG PHY initialization
is in progress waits for the wait queue instead of immediately returning
errors to PHY users. The IRQs were also disabled while waiting for the OTG
PHY initialization to complete, as the interrupt handler may also apply HW
settings.

The OTG can only be initialized once. It is initialized by the first PHY
that calls struct phy_ops::rcar_gen3_phy_usb2_init().

To avoid failures when multiple PHYs call struct
phy_ops::rcar_gen3_phy_usb2_init() simultaneously, and the PHY responsible
for initializing the OTG either fails or deinit quiqly and another PHY
takes over the PHY init role), the code waiting for the
channel->otg_init_done wait queue retries up to NUM_OF_PHYS times.

Fixes: 55a387ebb921 ("phy: renesas: rcar-gen3-usb2: Lock around hardware registers and driver data")
Cc: stable@vger.kernel.org
Reported-by: Pavel Machek <pavel@nabladev.com>
Closes: https://lore.kernel.org/all/afhkX2Ys2BG1gnqy@duo.ucw.cz
Reported-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Closes: https://lore.kernel.org/all/afhkX2Ys2BG1gnqy@duo.ucw.cz
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Link: https://lore.kernel.org/all/afhkX2Ys2BG1gnqy@duo.ucw.cz
Link: https://patch.msgid.link/20260716183246.3183877-1-claudiu.beznea+renesas@tuxon.dev
Signed-off-by: Vinod Koul <vkoul@kernel.org>

0 files changed, 0 insertions, 0 deletions