Re: [PATCH 20/25] dmaengine: dw-edma: Use non-atomic io-64 methods

[Serge Semin <fancer.lancer@gmail.com>]

On Fri, Mar 25, 2022 at 01:58:40PM +0530, Manivannan Sadhasivam wrote:
> On Thu, Mar 24, 2022 at 04:48:31AM +0300, Serge Semin wrote:
> > Instead of splitting the 64-bits IOs up into two 32-bits ones it's
> > possible to use an available set of the 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. Also note that if a platform
> > doesn't support 64-bit DBI IOs then the corresponding accessors will just
> > directly call the lo_hi_readq()/lo_hi_writeq() methods.
> > 
> > Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
> > ---
> >  drivers/dma/dw-edma/dw-edma-v0-core.c | 71 +++++++++------------------
> >  1 file changed, 24 insertions(+), 47 deletions(-)
> > 
> > diff --git a/drivers/dma/dw-edma/dw-edma-v0-core.c b/drivers/dma/dw-edma/dw-edma-v0-core.c
> > index 6b303d5a6b2a..ebb860e19c75 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 */
> > -
> >  #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 +178,25 @@ 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));
> > +	}
> > +
> > +	if (dw->chip->flags & DW_EDMA_CHIP_32BIT_DBI)
> > +		lo_hi_writeq(value, addr);
> > +	else
> >  		writeq(value, addr);
> >  
> > +	if (dw->chip->mf == EDMA_MF_EDMA_LEGACY)
> >  		raw_spin_unlock_irqrestore(&dw->lock, flags);
> > -	} else {
> > -		writeq(value, addr);
> > -	}
> >  }
> >  
> >  static inline u64 readq_ch(struct dw_edma *dw, enum dw_edma_dir dir, u16 ch,
> >  			   const void __iomem *addr)
> >  {
> > -	u32 value;
> > +	unsigned long flags;
> > +	u64 value;
> >  
> >  	if (dw->chip->mf == EDMA_MF_EDMA_LEGACY) {
> >  		u32 viewport_sel;
> > -		unsigned long flags;
> >  
> >  		raw_spin_lock_irqsave(&dw->lock, flags);
> >  
> > @@ -206,12 +206,15 @@ static inline u64 readq_ch(struct dw_edma *dw, enum dw_edma_dir dir, u16 ch,
> >  
> >  		writel(viewport_sel,
> >  		       &(__dw_regs(dw)->type.legacy.viewport_sel));
> > +	}
> > +
> > +	if (dw->chip->flags & DW_EDMA_CHIP_32BIT_DBI)
> > +		value = lo_hi_readq(addr);
> > +	else
> >  		value = readq(addr);
> >  
> > +	if (dw->chip->mf == EDMA_MF_EDMA_LEGACY)
> >  		raw_spin_unlock_irqrestore(&dw->lock, flags);
> > -	} else {
> > -		value = readq(addr);
> > -	}
> >  
> >  	return value;
> >  }
> > @@ -225,8 +228,6 @@ static inline u64 readq_ch(struct dw_edma *dw, enum dw_edma_dir dir, u16 ch,
> >  #define SET_LL_64(ll, value) \
> >  	writeq(value, ll)
> >  
> > -#endif /* CONFIG_64BIT */
> > -
> >  /* eDMA management callbacks */
> >  void dw_edma_v0_core_off(struct dw_edma *dw)
> >  {
> > @@ -325,19 +326,10 @@ static void dw_edma_v0_core_write_chunk(struct dw_edma_chunk *chunk)
> >  		/* Transfer size */
> >  		SET_LL_32(&lli[i].transfer_size, child->sz);
> >  		/* SAR */
> > -		#ifdef CONFIG_64BIT
> > -			SET_LL_64(&lli[i].sar.reg, child->sar);
> > -		#else /* CONFIG_64BIT */
> > -			SET_LL_32(&lli[i].sar.lsb, lower_32_bits(child->sar));
> > -			SET_LL_32(&lli[i].sar.msb, upper_32_bits(child->sar));
> > -		#endif /* CONFIG_64BIT */
> > +		SET_LL_64(&lli[i].sar.reg, child->sar);
> 

> This macro still uses writeq(), that's not available on 32bit platforms.
> Am I missing anything?

Yes, the writeq/readq macro are defined in the
include/linux/{io-64-nonatomic-lo-hi.h,io-64-nonatomic-hi-lo.h} files.
If the platform doesn't provide its own 64-bit IOs implementation
these macro are used and are unwrapped with the two writel/readl
methods.

-Sergey

> 
> Thanks,
> Mani
> 
> >  		/* DAR */
> > -		#ifdef CONFIG_64BIT
> > -			SET_LL_64(&lli[i].dar.reg, child->dar);
> > -		#else /* CONFIG_64BIT */
> > -			SET_LL_32(&lli[i].dar.lsb, lower_32_bits(child->dar));
> > -			SET_LL_32(&lli[i].dar.msb, upper_32_bits(child->dar));
> > -		#endif /* CONFIG_64BIT */
> > +		SET_LL_64(&lli[i].dar.reg, child->dar);
> > +
> >  		i++;
> >  	}
> >  
> > @@ -349,12 +341,7 @@ static void dw_edma_v0_core_write_chunk(struct dw_edma_chunk *chunk)
> >  	/* Channel control */
> >  	SET_LL_32(&llp->control, control);
> >  	/* Linked list */
> > -	#ifdef CONFIG_64BIT
> > -		SET_LL_64(&llp->llp.reg, chunk->ll_region.paddr);
> > -	#else /* CONFIG_64BIT */
> > -		SET_LL_32(&llp->llp.lsb, lower_32_bits(chunk->ll_region.paddr));
> > -		SET_LL_32(&llp->llp.msb, upper_32_bits(chunk->ll_region.paddr));
> > -	#endif /* CONFIG_64BIT */
> > +	SET_LL_64(&llp->llp.reg, chunk->ll_region.paddr);
> >  }
> >  
> >  void dw_edma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
> > @@ -417,18 +404,8 @@ void dw_edma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
> >  		SET_CH_32(dw, chan->dir, chan->id, ch_control1,
> >  			  (DW_EDMA_V0_CCS | DW_EDMA_V0_LLE));
> >  		/* Linked list */
> > -		if ((chan->dw->chip->flags & DW_EDMA_CHIP_32BIT_DBI) ||
> > -		    !IS_ENABLED(CONFIG_64BIT)) {
> > -			SET_CH_32(dw, chan->dir, chan->id, llp.lsb,
> > -				  lower_32_bits(chunk->ll_region.paddr));
> > -			SET_CH_32(dw, chan->dir, chan->id, llp.msb,
> > -				  upper_32_bits(chunk->ll_region.paddr));
> > -		} else {
> > -		#ifdef CONFIG_64BIT
> > -			SET_CH_64(dw, chan->dir, chan->id, llp.reg,
> > -				  chunk->ll_region.paddr);
> > -		#endif
> > -		}
> > +		SET_CH_64(dw, chan->dir, chan->id, llp.reg,
> > +			  chunk->ll_region.paddr);
> >  	}
> >  	/* Doorbell */
> >  	SET_RW_32(dw, chan->dir, doorbell,
> > -- 
> > 2.35.1
> >