Re: [PATCH v8 06/14] media: platform: Improve the implementation of the system PM ops

Tomasz Figa
2020-05-21T15:33:03Z

Hi Xia,

On Fri, Apr 03, 2020 at 05:40:25PM +0800, Xia Jiang wrote:
> Cancel reset hw operation in suspend and resume function because this
> will be done in device_run().

This and...

> Add spin_lock and unlock operation in irq and resume function to make
> sure that the current frame is processed completely before suspend.

...this are two separate changes. Please split.

>
> Signed-off-by: Xia Jiang <xia.jiang@mediatek.com>
> ---
> drivers/media/platform/mtk-jpeg/mtk_jpeg_core.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/platform/mtk-jpeg/mtk_jpeg_core.c b/drivers/media/platform/mtk-jpeg/mtk_jpeg_core.c
> index dd5cadd101ef..2fa3711fdc9b 100644
> --- a/drivers/media/platform/mtk-jpeg/mtk_jpeg_core.c
> +++ b/drivers/media/platform/mtk-jpeg/mtk_jpeg_core.c
> @@ -911,6 +911,8 @@ static irqreturn_t mtk_jpeg_dec_irq(int irq, void *priv)
> u32 dec_ret;
> int i;
>
> + spin_lock(&jpeg->hw_lock);
> +

nit: For consistency, it is recommended to always use the same, i.e. the
strongest, spin_(un)lock_ primitives when operating on the same spinlock.
In this case it would be the irqsave(restore) variants.

> dec_ret = mtk_jpeg_dec_get_int_status(jpeg->dec_reg_base);
> dec_irq_ret = mtk_jpeg_dec_enum_result(dec_ret);
> ctx = v4l2_m2m_get_curr_priv(jpeg->m2m_dev);
> @@ -941,6 +943,7 @@ static irqreturn_t mtk_jpeg_dec_irq(int irq, void *priv)
> v4l2_m2m_buf_done(src_buf, buf_state);
> v4l2_m2m_buf_done(dst_buf, buf_state);
> v4l2_m2m_job_finish(jpeg->m2m_dev, ctx->fh.m2m_ctx);
> + spin_unlock(&jpeg->hw_lock);
> pm_runtime_put_sync(ctx->jpeg->dev);
> return IRQ_HANDLED;
> }
> @@ -1191,7 +1194,6 @@ static __maybe_unused int mtk_jpeg_pm_suspend(struct device *dev)
> {
> struct mtk_jpeg_dev *jpeg = dev_get_drvdata(dev);
>
> - mtk_jpeg_dec_reset(jpeg->dec_reg_base);
> mtk_jpeg_clk_off(jpeg);
>
> return 0;
> @@ -1202,19 +1204,24 @@ static __maybe_unused int mtk_jpeg_pm_resume(struct device *dev)
> struct mtk_jpeg_dev *jpeg = dev_get_drvdata(dev);
>
> mtk_jpeg_clk_on(jpeg);
> - mtk_jpeg_dec_reset(jpeg->dec_reg_base);
>
> return 0;
> }
>
> static __maybe_unused int mtk_jpeg_suspend(struct device *dev)
> {
> + struct mtk_jpeg_dev *jpeg = dev_get_drvdata(dev);
> + unsigned long flags;
> int ret;
>
> if (pm_runtime_suspended(dev))
> return 0;
>
> + spin_lock_irqsave(&jpeg->hw_lock, flags);

What does this spinlock protect us from? I can see that it would prevent
the interrupt handler from being called, but is it okay to suspend the
system without handling the interrupt?

> +
> ret = mtk_jpeg_pm_suspend(dev);
> +

Looking at the implementation of mtk_jpeg_pm_suspend(), all it does is
disabling the clock. How do we make sure that there is no frame currently
being processed by the hardware?

Best regards,
Tomasz