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

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Date:   Wed, 27 May 2020 09:52:00 +0800
From:   Xia Jiang <xia.jiang@...iatek.com>
To:     Tomasz Figa <tfiga@...omium.org>
CC:     Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "Matthias Brugger" <matthias.bgg@...il.com>,
        Rick Chang <rick.chang@...iatek.com>,
        <linux-media@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        <srv_heupstream@...iatek.com>, <senozhatsky@...omium.org>,
        <mojahsu@...omium.org>, <drinkcat@...omium.org>,
        <maoguang.meng@...iatek.com>, <sj.huang@...iatek.com>
Subject: Re: [PATCH v8 06/14] media: platform: Improve the implementation of
 the system PM ops

On Thu, 2020-05-21 at 15:32 +0000, Tomasz Figa wrote:
> 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@...iatek.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?
Dear Tomasz,
I mean that if current image is processed in irq handler,suspend
function can not get the lock(it was locked in irq handler).Should I
move the spin_lock_irqsave(&jpeg->hw_lock, flags) to the start location
of suspend function or use wait_event_timeout() to handle the interrupt
before suspend?

Best Regards,
Xia Jiang
> 
> > +
> >  	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