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

[Bjorn Helgaas <helgaas@kernel.org>]

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@baikalelectronics.ru>
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> Acked-by: Vinod Koul <vkoul@kernel.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