Re: [PATCH v2 3/5] phy: renesas: rcar-gen3-usb2: Lock around hardware registers and driver data

On Tue, Feb 25, 2025 at 11:01 AM Claudiu claudiu.beznea@tuxon.dev wrote:

From: Claudiu Beznea claudiu.beznea.uj@bp.renesas.com

The phy-rcar-gen3-usb2 driver exposes four individual PHYs that are requested and configured by PHY users. The struct phy_ops APIs access the same set of registers to configure all PHYs. Additionally, PHY settings can be modified through sysfs or an IRQ handler. While some struct phy_ops APIs are protected by a driver-wide mutex, others rely on individual PHY-specific mutexes.

This approach can lead to various issues, including: 1/ the IRQ handler may interrupt PHY settings in progress, racing with hardware configuration protected by a mutex lock 2/ due to msleep(20) in rcar_gen3_init_otg(), while a configuration thread suspends to wait for the delay, another thread may try to configure another PHY (with phy_init() + phy_power_on()); re-running the phy_init() goes to the exact same configuration code, re-running the same hardware configuration on the same set of registers (and bits) which might impact the result of the msleep for the 1st configuring thread 3/ sysfs can configure the hardware (though role_store()) and it can still race with the phy_init()/phy_power_on() APIs calling into the drivers struct phy_ops

To address these issues, add a spinlock to protect hardware register access and driver private data structures (e.g., calls to rcar_gen3_is_any_rphy_initialized()). Checking driver-specific data remains necessary as all PHY instances share common settings. With this change, the existing mutex protection is removed and the cleanup.h helpers are used.

While at it, to keep the code simpler, do not skip regulator_enable()/regulator_disable() APIs in rcar_gen3_phy_usb2_power_on()/rcar_gen3_phy_usb2_power_off() as the regulators enable/disable operations are reference counted anyway.

Fixes: f3b5a8d9b50d ("phy: rcar-gen3-usb2: Add R-Car Gen3 USB2 PHY driver") Cc: stable@vger.kernel.org Reviewed-by: Yoshihiro Shimoda yoshihiro.shimoda.uh@renesas.com Tested-by: Yoshihiro Shimoda yoshihiro.shimoda.uh@renesas.com Signed-off-by: Claudiu Beznea claudiu.beznea.uj@bp.renesas.com

---

Changes in v2:

• collected tags

drivers/phy/renesas/phy-rcar-gen3-usb2.c | 49 +++++++++++++----------- 1 file changed, 26 insertions(+), 23 deletions(-)

Reviewed-by: Lad Prabhakar prabhakar.mahadev-lad.rj@bp.renesas.com

Cheers, Prabhakar

diff --git a/drivers/phy/renesas/phy-rcar-gen3-usb2.c b/drivers/phy/renesas/phy-rcar-gen3-usb2.c index 826c9c4dd4c0..5c0ceba09b67 100644 --- a/drivers/phy/renesas/phy-rcar-gen3-usb2.c +++ b/drivers/phy/renesas/phy-rcar-gen3-usb2.c @@ -9,6 +9,7 @@

• Copyright (C) 2014 Cogent Embedded, Inc.

*/

+#include <linux/cleanup.h> #include <linux/extcon-provider.h> #include <linux/interrupt.h> #include <linux/io.h> @@ -118,7 +119,7 @@ struct rcar_gen3_chan { struct regulator *vbus; struct reset_control *rstc; struct work_struct work;

•   struct mutex lock;      /* protects rphys[...].powered */
  

•   spinlock_t lock;        /* protects access to hardware and driver data structure. */
    enum usb_dr_mode dr_mode;
    u32 obint_enable_bits;
    bool extcon_host;
  

@@ -348,6 +349,8 @@ static ssize_t role_store(struct device *dev, struct device_attribute *attr, bool is_b_device; enum phy_mode cur_mode, new_mode;

•   guard(spinlock_irqsave)(&ch->lock);
  

•   if (!ch->is_otg_channel || !rcar_gen3_is_any_otg_rphy_initialized(ch))
            return -EIO;
  
  

@@ -415,7 +418,7 @@ static void rcar_gen3_init_otg(struct rcar_gen3_chan *ch) val = readl(usb2_base + USB2_ADPCTRL); writel(val | USB2_ADPCTRL_IDPULLUP, usb2_base + USB2_ADPCTRL); }

•   msleep(20);
  

•   mdelay(20);
  
    writel(0xffffffff, usb2_base + USB2_OBINTSTA);
    writel(ch->obint_enable_bits, usb2_base + USB2_OBINTEN);
  

@@ -436,12 +439,14 @@ static irqreturn_t rcar_gen3_phy_usb2_irq(int irq, void *_ch) if (pm_runtime_suspended(dev)) goto rpm_put;

•   status = readl(usb2_base + USB2_OBINTSTA);
  

•   if (status & ch->obint_enable_bits) {
  

•           dev_vdbg(dev, "%s: %08x\n", __func__, status);
  

•           writel(ch->obint_enable_bits, usb2_base + USB2_OBINTSTA);
  

•           rcar_gen3_device_recognition(ch);
  

•           ret = IRQ_HANDLED;
  

•   scoped_guard(spinlock, &ch->lock) {
  

•           status = readl(usb2_base + USB2_OBINTSTA);
  

•           if (status & ch->obint_enable_bits) {
  

•                   dev_vdbg(dev, "%s: %08x\n", __func__, status);
  

•                   writel(ch->obint_enable_bits, usb2_base + USB2_OBINTSTA);
  

•                   rcar_gen3_device_recognition(ch);
  

•                   ret = IRQ_HANDLED;
  

•           }
    }
  
  

rpm_put: @@ -456,6 +461,8 @@ static int rcar_gen3_phy_usb2_init(struct phy *p) void __iomem *usb2_base = channel->base; u32 val;

•   guard(spinlock_irqsave)(&channel->lock);
  

•   /* Initialize USB2 part */
    val = readl(usb2_base + USB2_INT_ENABLE);
    val |= USB2_INT_ENABLE_UCOM_INTEN | rphy->int_enable_bits;
  

@@ -479,6 +486,8 @@ static int rcar_gen3_phy_usb2_exit(struct phy *p) void __iomem *usb2_base = channel->base; u32 val;

•   guard(spinlock_irqsave)(&channel->lock);
  

•   rphy->initialized = false;
  
    val = readl(usb2_base + USB2_INT_ENABLE);
  

@@ -498,16 +507,17 @@ static int rcar_gen3_phy_usb2_power_on(struct phy *p) u32 val; int ret = 0;

•   mutex_lock(&channel->lock);
  

•   if (!rcar_gen3_are_all_rphys_power_off(channel))
  

•           goto out;
  

•   if (channel->vbus) {
            ret = regulator_enable(channel->vbus);
            if (ret)
  

•                   goto out;
  

•                   return ret;
    }
  
  

•   guard(spinlock_irqsave)(&channel->lock);
  

•   if (!rcar_gen3_are_all_rphys_power_off(channel))
  

•           goto out;
  

•   val = readl(usb2_base + USB2_USBCTR);
    val |= USB2_USBCTR_PLL_RST;
    writel(val, usb2_base + USB2_USBCTR);
  

@@ -517,7 +527,6 @@ static int rcar_gen3_phy_usb2_power_on(struct phy *p) out: /* The powered flag should be set for any other phys anyway */ rphy->powered = true;

•   mutex_unlock(&channel->lock);
  
    return 0;
  

} @@ -528,18 +537,12 @@ static int rcar_gen3_phy_usb2_power_off(struct phy *p) struct rcar_gen3_chan *channel = rphy->ch; int ret = 0;

•   mutex_lock(&channel->lock);
  

•   rphy->powered = false;
  

•   if (!rcar_gen3_are_all_rphys_power_off(channel))
  

•           goto out;
  

•   scoped_guard(spinlock_irqsave, &channel->lock)
  

•           rphy->powered = false;
  
    if (channel->vbus)
            ret = regulator_disable(channel->vbus);
  
  

-out:

•   mutex_unlock(&channel->lock);
  

•   return ret;
  

}

@@ -750,7 +753,7 @@ static int rcar_gen3_phy_usb2_probe(struct platform_device *pdev) if (phy_data->no_adp_ctrl) channel->obint_enable_bits = USB2_OBINT_IDCHG_EN;

•   mutex_init(&channel->lock);
  

•   spin_lock_init(&channel->lock);
    for (i = 0; i < NUM_OF_PHYS; i++) {
            channel->rphys[i].phy = devm_phy_create(dev, NULL,
                                                    phy_data->phy_usb2_ops);
  

-- 2.43.0