linux-kernel - Re: [PATCH v3 2/3] drm/bridge: analogix_dp: use jiffies to simulate timeout loop

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Date:   Mon, 12 Sep 2016 09:51:10 -0400
From:   Sean Paul <seanpaul@...omium.org>
To:     Yakir Yang <ykk@...k-chips.com>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Inki Dae <inki.dae@...sung.com>,
        David Airlie <airlied@...ux.ie>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Mika Kahola <mika.kahola@...el.com>,
        Stéphane Marchesin <marcheu@...omium.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Thierry Reding <treding@...dia.com>,
        Krzysztof Kozlowski <k.kozlowski@...sung.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Jingoo Han <jingoohan1@...il.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v3 2/3] drm/bridge: analogix_dp: use jiffies to simulate
 timeout loop

On Fri, Sep 9, 2016 at 5:44 AM, Yakir Yang <ykk@...k-chips.com> wrote:
> Signed-off-by: Yakir Yang <ykk@...k-chips.com>
> ---
> Changes in v3:
> - Suggested by Sean
>
> Changes in v2: None
>
>  drivers/gpu/drm/bridge/analogix/analogix_dp_core.h |  3 ++-
>  drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c  | 18 +++++++++---------
>  2 files changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
> index a15f076..d564e90 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
> @@ -16,10 +16,11 @@
>  #include <drm/drm_crtc.h>
>  #include <drm/drm_dp_helper.h>
>
> -#define DP_TIMEOUT_LOOP_COUNT 100
>  #define MAX_CR_LOOP 5
>  #define MAX_EQ_LOOP 5
>
> +#define DP_TIMEOUT_LOOP_MS                     msecs_to_jiffies(1)

The name suggests the units here are ms, but you're storing jiffies.
Do the msecs_to_jiffies conversion down below.

> +
>  /* DP_MAX_LANE_COUNT */
>  #define DPCD_ENHANCED_FRAME_CAP(x)             (((x) >> 7) & 0x1)
>  #define DPCD_MAX_LANE_COUNT(x)                 ((x) & 0x1f)
> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> index a4d17b8..15a4cf0 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> @@ -335,7 +335,7 @@ void analogix_dp_set_analog_power_down(struct analogix_dp_device *dp,
>  void analogix_dp_init_analog_func(struct analogix_dp_device *dp)
>  {
>         u32 reg;
> -       int timeout_loop = 0;
> +       unsigned long timeout;
>
>         analogix_dp_set_analog_power_down(dp, POWER_ALL, 0);
>
> @@ -350,9 +350,9 @@ void analogix_dp_init_analog_func(struct analogix_dp_device *dp)
>         if (analogix_dp_get_pll_lock_status(dp) == PLL_UNLOCKED) {
>                 analogix_dp_set_pll_power_down(dp, 0);
>
> +               timeout = jiffies + DP_TIMEOUT_LOOP_MS;

timeout = jiffies + msecs_to_jiffies(DP_TIMEOUT_LOOP_MS);

>                 while (analogix_dp_get_pll_lock_status(dp) == PLL_UNLOCKED) {
> -                       timeout_loop++;
> -                       if (DP_TIMEOUT_LOOP_COUNT < timeout_loop) {
> +                       if (time_after(jiffies, timeout)) {
>                                 dev_err(dp->dev, "failed to get pll lock status\n");
>                                 return;
>                         }
> @@ -501,7 +501,7 @@ int analogix_dp_start_aux_transaction(struct analogix_dp_device *dp)
>  {
>         int reg;
>         int retval = 0;
> -       int timeout_loop = 0;
> +       unsigned long timeout;
>
>         /* Enable AUX CH operation */
>         reg = readl(dp->reg_base + ANALOGIX_DP_AUX_CH_CTL_2);
> @@ -509,10 +509,10 @@ int analogix_dp_start_aux_transaction(struct analogix_dp_device *dp)
>         writel(reg, dp->reg_base + ANALOGIX_DP_AUX_CH_CTL_2);
>
>         /* Is AUX CH command reply received? */
> +       timeout = jiffies + DP_TIMEOUT_LOOP_MS;
>         reg = readl(dp->reg_base + ANALOGIX_DP_INT_STA);
>         while (!(reg & RPLY_RECEIV)) {
> -               timeout_loop++;
> -               if (DP_TIMEOUT_LOOP_COUNT < timeout_loop) {
> +               if (time_after(jiffies, timeout)) {
>                         dev_err(dp->dev, "AUX CH command reply failed!\n");
>                         return -ETIMEDOUT;
>                 }
> @@ -1055,7 +1055,7 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
>  {
>         u32 reg;
>         u8 *buffer = msg->buffer;
> -       int timeout_loop = 0;
> +       unsigned long timeout;
>         unsigned int i;
>         int num_transferred = 0;
>
> @@ -1123,10 +1123,10 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
>
>         /* Is AUX CH command reply received? */
>         /* TODO: Wait for an interrupt instead of looping? */
> +       timeout = jiffies + DP_TIMEOUT_LOOP_MS;
>         reg = readl(dp->reg_base + ANALOGIX_DP_INT_STA);
>         while (!(reg & RPLY_RECEIV)) {
> -               timeout_loop++;
> -               if (timeout_loop > DP_TIMEOUT_LOOP_COUNT) {
> +               if (time_after(jiffies, timeout)) {
>                         dev_err(dp->dev, "AUX CH command reply failed!\n");
>                         return -ETIMEDOUT;
>                 }
> --
> 1.9.1
>
>