linux-kernel - Re: [PATCH 12/25] dmaengine: dw-edma: Fix DebugFS reg entry type

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Message-ID: <20220324174859.GU2854@thinkpad>
Date:   Thu, 24 Mar 2022 23:18:59 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Vinod Koul <vkoul@...nel.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Frank Li <Frank.Li@....com>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        linux-pci@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 12/25] dmaengine: dw-edma: Fix DebugFS reg entry type

On Thu, Mar 24, 2022 at 04:48:23AM +0300, Serge Semin wrote:
> debugfs_entries structure declared in the dw-edma-v0-debugfs.c module
> contains the DebugFS node' register address. The address is declared as
> dma_addr_t type, but first it's assigned with virtual CPU IOMEM address
> and then it's cast back to the virtual address. Even though the castes
> sandwich will unlikely cause any problem since normally DMA address is at
> least of the same size as the CPU virtual address, it's at the very least
> redundant if not to say logically incorrect. Let's fix it by just stop
> casting the pointer back and worth and just preserve the address as a
> pointer to void with __iomem qualifier.
> 
> Fixes: 305aebeff879 ("dmaengine: Add Synopsys eDMA IP version 0 debugfs support")
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

Thanks,
Mani

> ---
>  drivers/dma/dw-edma/dw-edma-v0-debugfs.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/dma/dw-edma/dw-edma-v0-debugfs.c b/drivers/dma/dw-edma/dw-edma-v0-debugfs.c
> index 3a899f7f4e8d..12845a2dc016 100644
> --- a/drivers/dma/dw-edma/dw-edma-v0-debugfs.c
> +++ b/drivers/dma/dw-edma/dw-edma-v0-debugfs.c
> @@ -14,7 +14,7 @@
>  #include "dw-edma-core.h"
>  
>  #define REGS_ADDR(name) \
> -	((void __force *)&regs->name)
> +	((void __iomem *)&regs->name)
>  #define REGISTER(name) \
>  	{ #name, REGS_ADDR(name) }
>  
> @@ -48,12 +48,13 @@ static struct {
>  
>  struct debugfs_entries {
>  	const char				*name;
> -	dma_addr_t				*reg;
> +	void __iomem				*reg;
>  };
>  
>  static int dw_edma_debugfs_u32_get(void *data, u64 *val)
>  {
> -	void __iomem *reg = (void __force __iomem *)data;
> +	void __iomem *reg = data;
> +
>  	if (dw->chip->mf == EDMA_MF_EDMA_LEGACY &&
>  	    reg >= (void __iomem *)&regs->type.legacy.ch) {
>  		void __iomem *ptr = &regs->type.legacy.ch;
> -- 
> 2.35.1
>