[v2,2/2] dmaengine: dw-dmac: implement dma protection control setting

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Sat, Nov 10, 2018 at 05:28:31PM +0100, Christian Lamparter wrote:
> This patch adds a new device-tree property that allows to
> specify the dma protection control bits for the all of the
> DMA controller's channel uniformly.
> 
> Setting the "correct" bits can have a huge impact on the
> PPC460EX and APM82181 that use this DMA engine in combination
> with a DesignWare' SATA-II core (sata_dwc_460ex driver).
> 
> In the OpenWrt Forum, the user takimata reported that:
> |It seems your patch unleashed the full power of the SATA port.
> |Where I was previously hitting a really hard limit at around
> |82 MB/s for reading and 27 MB/s for writing, I am now getting this:
> |
> |root@OpenWrt:/mnt# time dd if=/dev/zero of=tempfile bs=1M count=1024
> |1024+0 records in
> |1024+0 records out
> |real    0m 13.65s
> |user    0m 0.01s
> |sys     0m 11.89s
> |
> |root@OpenWrt:/mnt# time dd if=tempfile of=/dev/null bs=1M count=1024
> |1024+0 records in
> |1024+0 records out
> |real    0m 8.41s
> |user    0m 0.01s
> |sys     0m 4.70s
> |
> |This means: 121 MB/s reading and 75 MB/s writing!
> |
> |The drive is a WD Green WD10EARX taken from an older MBL Single.
> |I repeated the test a few times with even larger files to rule out
> |any caching, I'm still seeing the same great performance. OpenWrt is
> |now completely on par with the original MBL firmware's performance.
> 
> Another user And.short reported:
> |I can report that your fix worked! Boots up fine with two
> |drives even with more partitions, and no more reboot on
> |concurrent disk access!
> 
> A closer look into the sata_dwc_460ex code revealed that
> the driver did initally set the correct protection control
> bits. However, this feature was lost when the sata_dwc_460ex
> driver was converted to the generic DMA driver framework.

LGTM, though minor style comment below.

> 
> BugLink: https://forum.openwrt.org/t/wd-mybook-live-duo-two-disks/16195/55
> BugLink: https://forum.openwrt.org/t/wd-mybook-live-duo-two-disks/16195/50
> Fixes: 8b3444852a2b ("sata_dwc_460ex: move to generic DMA driver")
> Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
> ---
>  drivers/dma/dw/core.c                | 2 ++
>  drivers/dma/dw/platform.c            | 6 ++++++
>  drivers/dma/dw/regs.h                | 4 ++++
>  include/linux/platform_data/dma-dw.h | 6 ++++++
>  4 files changed, 18 insertions(+)
> 
> diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
> index f43e6dafe446..0772d2d6cc68 100644
> --- a/drivers/dma/dw/core.c
> +++ b/drivers/dma/dw/core.c
> @@ -160,12 +160,14 @@ static void dwc_initialize_chan_idma32(struct dw_dma_chan *dwc)
>  
>  static void dwc_initialize_chan_dw(struct dw_dma_chan *dwc)
>  {
> +	struct dw_dma *dw = to_dw_dma(dwc->chan.device);
>  	u32 cfghi = DWC_CFGH_FIFO_MODE;
>  	u32 cfglo = DWC_CFGL_CH_PRIOR(dwc->priority);
>  	bool hs_polarity = dwc->dws.hs_polarity;
>  
>  	cfghi |= DWC_CFGH_DST_PER(dwc->dws.dst_id);
>  	cfghi |= DWC_CFGH_SRC_PER(dwc->dws.src_id);
> +	cfghi |= DWC_CFGH_PROTCTL(dw->pdata->protctl);
>  
>  	/* Set polarity of handshake interface */
>  	cfglo |= hs_polarity ? DWC_CFGL_HS_DST_POL | DWC_CFGL_HS_SRC_POL : 0;
> diff --git a/drivers/dma/dw/platform.c b/drivers/dma/dw/platform.c
> index f62dd0944908..c299ff181bb6 100644
> --- a/drivers/dma/dw/platform.c
> +++ b/drivers/dma/dw/platform.c
> @@ -162,6 +162,12 @@ dw_dma_parse_dt(struct platform_device *pdev)
>  			pdata->multi_block[tmp] = 1;
>  	}
>  
> +	if (!of_property_read_u32(np, "snps,dma-protection-control", &tmp)) {
> +		if (tmp > CHAN_PROTCTL_MASK)
> +			return NULL;
> +		pdata->protctl = tmp;
> +	}
> +
>  	return pdata;
>  }
>  #else
> diff --git a/drivers/dma/dw/regs.h b/drivers/dma/dw/regs.h
> index 09e7dfdbb790..646c9c960c07 100644
> --- a/drivers/dma/dw/regs.h
> +++ b/drivers/dma/dw/regs.h
> @@ -200,6 +200,10 @@ enum dw_dma_msize {
>  #define DWC_CFGH_FCMODE		(1 << 0)
>  #define DWC_CFGH_FIFO_MODE	(1 << 1)
>  #define DWC_CFGH_PROTCTL(x)	((x) << 2)
> +#define DWC_CFGH_PROTCTL_DATA	(0 << 2)	/* data access - always set */
> +#define DWC_CFGH_PROTCTL_PRIV	(1 << 2)	/* privileged -> AHB HPROT[1] */
> +#define DWC_CFGH_PROTCTL_BUFFER	(2 << 2)	/* bufferable -> AHB HPROT[2] */
> +#define DWC_CFGH_PROTCTL_CACHE	(4 << 2)	/* cacheable  -> AHB HPROT[3] */
>  #define DWC_CFGH_DS_UPD_EN	(1 << 5)
>  #define DWC_CFGH_SS_UPD_EN	(1 << 6)
>  #define DWC_CFGH_SRC_PER(x)	((x) << 7)
> diff --git a/include/linux/platform_data/dma-dw.h b/include/linux/platform_data/dma-dw.h
> index 896cb71a382c..b7b9d4a56bb0 100644
> --- a/include/linux/platform_data/dma-dw.h
> +++ b/include/linux/platform_data/dma-dw.h
> @@ -49,6 +49,7 @@ struct dw_dma_slave {
>   * @data_width: Maximum data width supported by hardware per AHB master
>   *		(in bytes, power of 2)
>   * @multi_block: Multi block transfers supported by hardware per channel.
> + * @protctl:	Protection control signals setting per channel.
>   */
>  struct dw_dma_platform_data {
>  	unsigned int	nr_channels;
> @@ -65,6 +66,11 @@ struct dw_dma_platform_data {
>  	unsigned char	nr_masters;
>  	unsigned char	data_width[DW_DMA_MAX_NR_MASTERS];
>  	unsigned char	multi_block[DW_DMA_MAX_NR_CHANNELS];
> +#define CHAN_PROTCTL_PRIVILEGED		BIT(0)
> +#define CHAN_PROTCTL_BUFFERABLE		BIT(1)
> +#define CHAN_PROTCTL_CACHEABLE		BIT(2)
> +#define	CHAN_PROTCTL_MASK		GENMASK(2, 0)

TAB vs. SPACE.

> +	unsigned char	protctl;
>  };
>  
>  #endif /* _PLATFORM_DATA_DMA_DW_H */
> -- 
> 2.19.1
>