linux-kernel - Re: [PATCH] PCI: dwc: Use the correct sleep function in wait_for

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Message-ID: <buqxbxlsngec2iz4oag7mfgva5cozk66ljfa6aatao6liepnzu@zlmtq2v2ib3m>
Date: Thu, 15 Feb 2024 17:17:12 +0300
From: Serge Semin <fancer.lancer@...il.com>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: Jingoo Han <jingoohan1@...il.com>, 
	Gustavo Pimentel <gustavo.pimentel@...opsys.com>, Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczyński <kw@...ux.com>, 
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Johan Hovold <johan+linaro@...nel.org>
Subject: Re: [PATCH] PCI: dwc: Use the correct sleep function in wait_for_link

On Thu, Feb 15, 2024 at 11:39:31AM +0100, Konrad Dybcio wrote:
> According to [1], msleep should be used for large sleeps, such as the
> 100-ish ms one in this function. Comply with the guide and use it.
> 
> [1] https://www.kernel.org/doc/Documentation/timers/timers-howto.txt
> 
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
> Tested on Qualcomm SC8280XP CRD
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 2 +-
>  drivers/pci/controller/dwc/pcie-designware.h | 3 +--
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 250cf7f40b85..abce6afceb91 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -655,7 +655,7 @@ int dw_pcie_wait_for_link(struct dw_pcie *pci)
>  		if (dw_pcie_link_up(pci))
>  			break;
>  
> -		usleep_range(LINK_WAIT_USLEEP_MIN, LINK_WAIT_USLEEP_MAX);
> +		msleep(LINK_WAIT_MSLEEP_MAX);
>  	}
>  
>  	if (retries >= LINK_WAIT_MAX_RETRIES) {
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 26dae4837462..3f145d6a8a31 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -63,8 +63,7 @@
>  
>  /* Parameters for the waiting for link up routine */
>  #define LINK_WAIT_MAX_RETRIES		10
> -#define LINK_WAIT_USLEEP_MIN		90000
> -#define LINK_WAIT_USLEEP_MAX		100000

> +#define LINK_WAIT_MSLEEP_MAX		100

Why do you use the _MAX suffix here? AFAICS any the timers normally
ensures the lower boundary value of the wait-duration, not the upper
one. So the more correct suffix would be _MIN. On the other hand, as
Alexander correctly noted, using fsleep() would be more suitable at
least from the maintainability point of view. Thus having a macro name
like LINK_WAIT_USLEEP_MIN or just LINK_WAIT_SLEEP_US would be more
appropriate. The later version is more preferable IMO.

-Serge(y)

>  
>  /* Parameters for the waiting for iATU enabled routine */
>  #define LINK_WAIT_MAX_IATU_RETRIES	5
> 
> ---
> base-commit: 26d7d52b6253574d5b6fec16a93e1110d1489cef
> change-id: 20240215-topic-pci_sleep-368108a1fb6f
> 
> Best regards,
> -- 
> Konrad Dybcio <konrad.dybcio@...aro.org>
> 
>