linux-kernel - Re: [PATCH v2] dmaengine: dw-edma: Remove runtime PM support

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Message-ID: <YzXQ+L27SKA2NOrd@matsya>
Date:   Thu, 29 Sep 2022 22:38:08 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     gustavo.pimentel@...opsys.com, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Serge Semin <fancer.lancer@...il.com>,
        Frank Li <Frank.Li@....com>
Subject: Re: [PATCH v2] dmaengine: dw-edma: Remove runtime PM support

On 10-09-22, 11:17, Manivannan Sadhasivam wrote:
> Currently, the dw-edma driver enables the runtime_pm for parent device
> (chip->dev) and increments/decrements the refcount during alloc/free
> chan resources callbacks.
> 
> This leads to a problem when the eDMA driver has been probed, but the
> channels were not used. This scenario can happen when the DW PCIe driver
> probes eDMA driver successfully, but the PCI EPF driver decides not to
> use eDMA channels and use iATU instead for PCI transfers.
> 
> In this case, the underlying device would be runtime suspended due to
> pm_runtime_enable() in dw_edma_probe() and the PCI EPF driver would have
> no knowledge of it.
> 
> Ideally, the eDMA driver should not be the one doing the runtime PM of
> the parent device. The responsibility should instead belong to the client
> drivers like PCI EPF.
> 
> So let's remove the runtime PM support from eDMA driver.

Applied, thanks

-- 
~Vinod