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[PATCH v1] spi: spi-mtk-nor: Add recovery mechanism for dma read timeout

Bayi Cheng posted 1 patch 1 year, 4 months ago
There is a newer version of this series
drivers/spi/spi-mtk-nor.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
[PATCH v1] spi: spi-mtk-nor: Add recovery mechanism for dma read timeout
Posted by Bayi Cheng 1 year, 4 months ago 
From: bayi cheng <bayi.cheng@mediatek.com>

The state machine of MTK spi nor controller may be disturbed by some
glitch signals from the relevant BUS during dma read, Although the
possibility of causing the dma read to fail is next to nothing,
However, if error-handling is not implemented, which makes the feature
somewhat risky.

Add an error-handling mechanism here, reset the state machine and
re-read the data when an error occurs.

Signed-off-by: bayi cheng <bayi.cheng@mediatek.com>
---
Change in v1:
  -Reset the state machine when dma read fails and read again.
---
---
 drivers/spi/spi-mtk-nor.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-mtk-nor.c b/drivers/spi/spi-mtk-nor.c
index d167699a1a96..c77d79da9a4c 100644
--- a/drivers/spi/spi-mtk-nor.c
+++ b/drivers/spi/spi-mtk-nor.c
@@ -80,6 +80,9 @@
 #define MTK_NOR_REG_DMA_FADR		0x71c
 #define MTK_NOR_REG_DMA_DADR		0x720
 #define MTK_NOR_REG_DMA_END_DADR	0x724
+#define MTK_NOR_REG_CG_DIS		0x728
+#define MTK_NOR_SFC_SW_RST		BIT(2)
+
 #define MTK_NOR_REG_DMA_DADR_HB		0x738
 #define MTK_NOR_REG_DMA_END_DADR_HB	0x73c
 
@@ -616,7 +619,18 @@ static int mtk_nor_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
 			mtk_nor_set_addr(sp, op);
 			return mtk_nor_read_pio(sp, op);
 		} else {
-			return mtk_nor_read_dma(sp, op);
+			ret = mtk_nor_read_dma(sp, op);
+			if (ret) {
+				dev_err(sp->dev, "try to read again\n");
+				mtk_nor_rmw(sp, MTK_NOR_REG_CG_DIS, 0, MTK_NOR_SFC_SW_RST);
+				mb(); /* flush previous writes */
+				mtk_nor_rmw(sp, MTK_NOR_REG_CG_DIS, MTK_NOR_SFC_SW_RST, 0);
+				mb(); /* flush previous writes */
+				writel(MTK_NOR_ENABLE_SF_CMD, sp->base + MTK_NOR_REG_WP);
+				mtk_nor_setup_bus(sp, op);
+				ret = mtk_nor_read_dma(sp, op);
+			}
+			return ret;
 		}
 	}
 
-- 
2.18.0
Re: [PATCH v1] spi: spi-mtk-nor: Add recovery mechanism for dma read timeout
Posted by AngeloGioacchino Del Regno 1 year, 4 months ago 
Il 05/12/22 09:24, Bayi Cheng ha scritto:
> From: bayi cheng <bayi.cheng@mediatek.com>
> 
> The state machine of MTK spi nor controller may be disturbed by some
> glitch signals from the relevant BUS during dma read, Although the
> possibility of causing the dma read to fail is next to nothing,
> However, if error-handling is not implemented, which makes the feature
> somewhat risky.
> 
> Add an error-handling mechanism here, reset the state machine and
> re-read the data when an error occurs.
> 
> Signed-off-by: bayi cheng <bayi.cheng@mediatek.com>
> ---
> Change in v1:
>    -Reset the state machine when dma read fails and read again.
> ---
> ---
>   drivers/spi/spi-mtk-nor.c | 16 +++++++++++++++-
>   1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-mtk-nor.c b/drivers/spi/spi-mtk-nor.c
> index d167699a1a96..c77d79da9a4c 100644
> --- a/drivers/spi/spi-mtk-nor.c
> +++ b/drivers/spi/spi-mtk-nor.c
> @@ -80,6 +80,9 @@
>   #define MTK_NOR_REG_DMA_FADR		0x71c
>   #define MTK_NOR_REG_DMA_DADR		0x720
>   #define MTK_NOR_REG_DMA_END_DADR	0x724
> +#define MTK_NOR_REG_CG_DIS		0x728
> +#define MTK_NOR_SFC_SW_RST		BIT(2)
> +
>   #define MTK_NOR_REG_DMA_DADR_HB		0x738
>   #define MTK_NOR_REG_DMA_END_DADR_HB	0x73c
>   
> @@ -616,7 +619,18 @@ static int mtk_nor_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
>   			mtk_nor_set_addr(sp, op);
>   			return mtk_nor_read_pio(sp, op);
>   		} else {
> -			return mtk_nor_read_dma(sp, op);
> +			ret = mtk_nor_read_dma(sp, op);
> +			if (ret) {
> +				dev_err(sp->dev, "try to read again\n");
> +				mtk_nor_rmw(sp, MTK_NOR_REG_CG_DIS, 0, MTK_NOR_SFC_SW_RST);
> +				mb(); /* flush previous writes */
> +				mtk_nor_rmw(sp, MTK_NOR_REG_CG_DIS, MTK_NOR_SFC_SW_RST, 0);
> +				mb(); /* flush previous writes */
> +				writel(MTK_NOR_ENABLE_SF_CMD, sp->base + MTK_NOR_REG_WP);

 From what I understand, you're introducing a way to perform a flush+reset on
the controller.

At this point, I'd put that in a separate function like `mtk_nor_reset()`, as
to both increase readability and to possibly reuse it somewhere else in the
future, if needed.

So this would become...

		} else {
			ret = mtk_nor_read_dma(sp, op);
			if (unlikely(ret)) {
				/* Handle rare bus glitch */
				mtk_nor_reset(sp);
				mtk_nor_setup_bus(sp, op);
				return mtk_nor_read_dma(sp, op);
			}
			return ret;
		}

...or something alike :-)

Regards,
Angelo
Re: [PATCH v1] spi: spi-mtk-nor: Add recovery mechanism for dma read timeout
Posted by Bayi Cheng (程八意) 1 year, 4 months ago 
On Mon, 2022-12-05 at 15:01 +0100, AngeloGioacchino Del Regno wrote:
> Il 05/12/22 09:24, Bayi Cheng ha scritto:
> > From: bayi cheng <bayi.cheng@mediatek.com>
> > 
> > The state machine of MTK spi nor controller may be disturbed by
> > some
> > glitch signals from the relevant BUS during dma read, Although the
> > possibility of causing the dma read to fail is next to nothing,
> > However, if error-handling is not implemented, which makes the
> > feature
> > somewhat risky.
> > 
> > Add an error-handling mechanism here, reset the state machine and
> > re-read the data when an error occurs.
> > 
> > Signed-off-by: bayi cheng <bayi.cheng@mediatek.com>
> > ---
> > Change in v1:
> >    -Reset the state machine when dma read fails and read again.
> > ---
> > ---
> >   drivers/spi/spi-mtk-nor.c | 16 +++++++++++++++-
> >   1 file changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/spi/spi-mtk-nor.c b/drivers/spi/spi-mtk-nor.c
> > index d167699a1a96..c77d79da9a4c 100644
> > --- a/drivers/spi/spi-mtk-nor.c
> > +++ b/drivers/spi/spi-mtk-nor.c
> > @@ -80,6 +80,9 @@
> >   #define MTK_NOR_REG_DMA_FADR		0x71c
> >   #define MTK_NOR_REG_DMA_DADR		0x720
> >   #define MTK_NOR_REG_DMA_END_DADR	0x724
> > +#define MTK_NOR_REG_CG_DIS		0x728
> > +#define MTK_NOR_SFC_SW_RST		BIT(2)
> > +
> >   #define MTK_NOR_REG_DMA_DADR_HB		0x738
> >   #define MTK_NOR_REG_DMA_END_DADR_HB	0x73c
> >   
> > @@ -616,7 +619,18 @@ static int mtk_nor_exec_op(struct spi_mem
> > *mem, const struct spi_mem_op *op)
> >   			mtk_nor_set_addr(sp, op);
> >   			return mtk_nor_read_pio(sp, op);
> >   		} else {
> > -			return mtk_nor_read_dma(sp, op);
> > +			ret = mtk_nor_read_dma(sp, op);
> > +			if (ret) {
> > +				dev_err(sp->dev, "try to read
> > again\n");
> > +				mtk_nor_rmw(sp, MTK_NOR_REG_CG_DIS, 0,
> > MTK_NOR_SFC_SW_RST);
> > +				mb(); /* flush previous writes */
> > +				mtk_nor_rmw(sp, MTK_NOR_REG_CG_DIS,
> > MTK_NOR_SFC_SW_RST, 0);
> > +				mb(); /* flush previous writes */
> > +				writel(MTK_NOR_ENABLE_SF_CMD, sp->base
> > + MTK_NOR_REG_WP);
> 
>  From what I understand, you're introducing a way to perform a
> flush+reset on
> the controller.
> 
> At this point, I'd put that in a separate function like
> `mtk_nor_reset()`, as
> to both increase readability and to possibly reuse it somewhere else
> in the
> future, if needed.
> 
> So this would become...
> 
> 		} else {
> 			ret = mtk_nor_read_dma(sp, op);
> 			if (unlikely(ret)) {
> 				/* Handle rare bus glitch */
> 				mtk_nor_reset(sp);
> 				mtk_nor_setup_bus(sp, op);
> 				return mtk_nor_read_dma(sp, op);
> 			}
> 			return ret;
> 		}
> 
> ...or something alike :-)
> 
> Regards,
> Angelo
> 
Hi Angelo,

Thanks for your comments! I will fix it in the next patch.

Regards,
Bayi

Patchew 2.1-devel-0870f84

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