linux-kernel - Re: [PATCH v9 19/27] dmaengine: dw-edma: Use non-atomic io-64 methods

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20230121005401.GA686892@bhelgaas>
Date:   Fri, 20 Jan 2023 18:54:01 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Vinod Koul <vkoul@...nel.org>, Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Cai Huoqing <cai.huoqing@...ux.dev>,
        Robin Murphy <robin.murphy@....com>,
        Jingoo Han <jingoohan1@...il.com>, Frank Li <Frank.Li@....com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Krzysztof Wilczyński <kw@...ux.com>,
        caihuoqing <caihuoqing@...du.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        linux-pci@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 19/27] dmaengine: dw-edma: Use non-atomic io-64 methods

On Fri, Jan 13, 2023 at 08:14:01PM +0300, Serge Semin wrote:
> Instead of splitting the 64-bits IOs up into two 32-bits ones it's
> possible to use the already available non-atomic readq/writeq methods
> implemented exactly for such cases. They are defined in the dedicated
> header files io-64-nonatomic-lo-hi.h/io-64-nonatomic-hi-lo.h. So in case
> if the 64-bits readq/writeq methods are unavailable on some platforms at
> consideration, the corresponding drivers can have any of these headers
> included and stop locally re-implementing the 64-bits IO accessors taking
> into account the non-atomic nature of the included methods. Let's do that
> in the DW eDMA driver too. Note by doing so we can discard the
> CONFIG_64BIT config ifdefs from the code.
> 
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> Acked-by: Vinod Koul <vkoul@...nel.org>
> ---
>  drivers/dma/dw-edma/dw-edma-v0-core.c | 55 +++++++++------------------
>  1 file changed, 18 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/dma/dw-edma/dw-edma-v0-core.c b/drivers/dma/dw-edma/dw-edma-v0-core.c
> index 66f296daac5a..51a34b43434c 100644
> --- a/drivers/dma/dw-edma/dw-edma-v0-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-v0-core.c
> @@ -8,6 +8,8 @@
>  
>  #include <linux/bitfield.h>
>  
> +#include <linux/io-64-nonatomic-lo-hi.h>
> +
>  #include "dw-edma-core.h"
>  #include "dw-edma-v0-core.h"
>  #include "dw-edma-v0-regs.h"
> @@ -53,8 +55,6 @@ static inline struct dw_edma_v0_regs __iomem *__dw_regs(struct dw_edma *dw)
>  		SET_32(dw, rd_##name, value);		\
>  	} while (0)
>  
> -#ifdef CONFIG_64BIT
> -
>  #define SET_64(dw, name, value)				\
>  	writeq(value, &(__dw_regs(dw)->name))
>  
> @@ -80,8 +80,6 @@ static inline struct dw_edma_v0_regs __iomem *__dw_regs(struct dw_edma *dw)
>  		SET_64(dw, rd_##name, value);		\
>  	} while (0)
>  
> -#endif /* CONFIG_64BIT */

Great to get rid of these #ifdefs!

Am I missing something?  It looks like SET_64 is used only by
SET_RW_64 and SET_BOTH_64, and neither of *them is used at all.

Similarly for GET_64 and GET_RW_64.

So maybe we could get rid of everything inside the #ifdefs as well?

>  #define SET_COMPAT(dw, name, value)			\
>  	writel(value, &(__dw_regs(dw)->type.unroll.name))
>  
> @@ -164,14 +162,13 @@ static inline u32 readl_ch(struct dw_edma *dw, enum dw_edma_dir dir, u16 ch,
>  #define SET_LL_32(ll, value) \
>  	writel(value, ll)
>  
> -#ifdef CONFIG_64BIT
> -
>  static inline void writeq_ch(struct dw_edma *dw, enum dw_edma_dir dir, u16 ch,
>  			     u64 value, void __iomem *addr)
>  {
> +	unsigned long flags;
> +
>  	if (dw->chip->mf == EDMA_MF_EDMA_LEGACY) {
>  		u32 viewport_sel;
> -		unsigned long flags;
>  
>  		raw_spin_lock_irqsave(&dw->lock, flags);
>  
> @@ -181,22 +178,22 @@ static inline void writeq_ch(struct dw_edma *dw, enum dw_edma_dir dir, u16 ch,
>  
>  		writel(viewport_sel,
>  		       &(__dw_regs(dw)->type.legacy.viewport_sel));
> -		writeq(value, addr);
> +	}
> +
> +	writeq(value, addr);
>  
> +	if (dw->chip->mf == EDMA_MF_EDMA_LEGACY)
>  		raw_spin_unlock_irqrestore(&dw->lock, flags);
> -	} else {
> -		writeq(value, addr);
> -	}

This is basically a cosmetic change unrelated to the commit log.  I
don't really object to the change, although I think it's of dubious
value to remove the repetition of the writeq() at the cost of adding
another "if" and unlock.

Lorenzo already applied this, so it's OK as-is unless you think it's
worth reworking to drop the unused stuff mentioned above, in which
case this rearrangement could be moved to a separate patch to make
both of them more focused.

Bjorn