linux-kernel - Re: [PATCH v10 01/11] drm/etnaviv: Add a dedicated function to register an irq handler

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Message-ID: <21f781a548cef63312df56cb2265de9a7c9a0901.camel@pengutronix.de>
Date:   Wed, 21 Jun 2023 12:16:26 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Sui Jingfeng <suijingfeng@...ngson.cn>,
        Sui Jingfeng <18949883232@....com>,
        Russell King <linux+etnaviv@...linux.org.uk>,
        Christian Gmeiner <christian.gmeiner@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        etnaviv@...ts.freedesktop.org
Subject: Re: [PATCH v10 01/11] drm/etnaviv: Add a dedicated function to
 register an irq handler

Am Mittwoch, dem 21.06.2023 um 17:20 +0800 schrieb Sui Jingfeng:
> Hi,
> 
> On 2023/6/21 17:07, Lucas Stach wrote:
> > Am Dienstag, dem 20.06.2023 um 17:47 +0800 schrieb Sui Jingfeng:
> > > From: Sui Jingfeng <suijingfeng@...ngson.cn>
> > > 
> > > Because getting IRQ from a device is platform-dependent, PCI devices have
> > > different methods for getting an IRQ. This patch is a preparation to extend
> > > this driver for supporting the PCI devices.
> > > 
> > > Cc: Lucas Stach <l.stach@...gutronix.de>
> > > Cc: Christian Gmeiner <christian.gmeiner@...il.com>
> > > Cc: Philipp Zabel <p.zabel@...gutronix.de>
> > > Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> > > Cc: Daniel Vetter <daniel@...ll.ch>
> > > Signed-off-by: Sui Jingfeng <suijingfeng@...ngson.cn>
> > > ---
> > >   drivers/gpu/drm/etnaviv/etnaviv_gpu.c | 32 +++++++++++++++++++--------
> > >   1 file changed, 23 insertions(+), 9 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> > > index de8c9894967c..a03e81337d8f 100644
> > > --- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> > > +++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
> > > @@ -1817,6 +1817,27 @@ static const struct of_device_id etnaviv_gpu_match[] = {
> > >   };
> > >   MODULE_DEVICE_TABLE(of, etnaviv_gpu_match);
> > >   
> > > +static int etnaviv_gpu_register_irq(struct etnaviv_gpu *gpu, int irq)
> > > +{
> > > +	struct device *dev = gpu->dev;
> > > +	int err;
> > > +
> > > +	if (irq < 0)
> > > +		return irq;
> > > +
> > > +	err = devm_request_irq(dev, irq, irq_handler, 0, dev_name(dev), gpu);
> > > +	if (err) {
> > > +		dev_err(dev, "failed to request irq %u: %d\n", irq, err);
> > > +		return err;
> > > +	}
> > > +
> > > +	gpu->irq = irq;
> > > +
> > > +	dev_info(dev, "irq(%d) handler registered\n", irq);
> > There is no reason to put this into the kernel log.
> 
> I want to see the IRQ of the device when debugging,
> 
> etnaviv actually print very less.
> 
> This serve as a minimal signal  to us the etnaviv_gpu_register_irq() 
> function is successful at driver load time.
> 
And debugging is a very different use-case than normal operation. If
it's needed at all, downgrade this to dev_dbg. This isn't interesting
information for a ordinary user of a system.

> >   It's no different
> > than other resources to the driver and we don't log each one of those
> > either.
> > 
> > In fact I don't see any reason for this change in the first place.
> > Effectively you are moving a single function call into a new function,
> > which doesn't seem like an improvement.
> 
> This is to make the patch easy to review, each patch is only introduce a 
> small function,
> 
What I'm saying is that I don't see the need to introduce this function
at all. All you need to do is move platform_get_irq out into the
platform device code path. The devm_request_irq can stay where it is,
as the only difference between platform and PCI device is how the irq
number is retrieved from the platform.

Regards,
Lucas

> which is paving the way for we introducing the PCI device driver.
> 
> Otherwise when we introducing the PCI device driver, the patch is looks 
> ugly,
> 
> It is difficult to review.
> 
> > Regards,
> > Lucas
> > 
> > > +
> > > +	return 0;
> > > +}
> > > +
> > >   static int etnaviv_gpu_platform_probe(struct platform_device *pdev)
> > >   {
> > >   	struct device *dev = &pdev->dev;
> > > @@ -1837,16 +1858,9 @@ static int etnaviv_gpu_platform_probe(struct platform_device *pdev)
> > >   		return PTR_ERR(gpu->mmio);
> > >   
> > >   	/* Get Interrupt: */
> > > -	gpu->irq = platform_get_irq(pdev, 0);
> > > -	if (gpu->irq < 0)
> > > -		return gpu->irq;
> > > -
> > > -	err = devm_request_irq(&pdev->dev, gpu->irq, irq_handler, 0,
> > > -			       dev_name(gpu->dev), gpu);
> > > -	if (err) {
> > > -		dev_err(dev, "failed to request IRQ%u: %d\n", gpu->irq, err);
> > > +	err = etnaviv_gpu_register_irq(gpu, platform_get_irq(pdev, 0));
> > > +	if (err)
> > >   		return err;
> > > -	}
> > >   
> > >   	/* Get Clocks: */
> > >   	gpu->clk_reg = devm_clk_get_optional(&pdev->dev, "reg");
>