linux-kernel - Re: [PATCH 2/2] spi: fix the divide by 0 error when calculating xfer waiting time

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Message-ID: <20201231032337.GA7980@yilunxu-OptiPlex-7050>
Date:   Thu, 31 Dec 2020 11:23:37 +0800
From:   Xu Yilun <yilun.xu@...el.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     linux-spi@...r.kernel.org, trix@...hat.com, lgoncalv@...hat.com,
        hao.wu@...el.com, matthew.gerlach@...ux.intel.com,
        russell.h.weight@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] spi: fix the divide by 0 error when calculating xfer
  waiting time

On Wed, Dec 30, 2020 at 01:46:44PM +0000, Mark Brown wrote:
> On Wed, Dec 30, 2020 at 10:24:20AM +0800, Xu Yilun wrote:
> > On Tue, Dec 29, 2020 at 01:13:08PM +0000, Mark Brown wrote:
> 
> > > Does this still apply with current code?  There have been some fixes in
> > > this area which I think should ensure that we don't turn the speed down
> > > to 0 if the controller doesn't supply a limit IIRC.
> 
> > Yes, there is chance the speed is set to 0, some related code from 5.11-rc1
> 
> Please check the code in the SPI tree and -next.

I see the fix patches in maillist, thanks.

> 
> > BTW, Could we keep the spi->max_speed_hz if no controller->max_speed_hz?
> > Always clamp the spi->max_speed_hz to 0 makes no sense.
> 
> Right, that's the fix.

Seems it still doesn't fix the case that neither controller nor client dev
provides the non-zero max_speed_hz. Do you think the patch is still
necessary?

Thanks,
Yilun