linux-kernel - Re: [PATCH 8/9] mtd: fsl-quadspi: disable AHB buffer prefetch

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Message-ID: <DB5PR0401MB184588E6C33FD167783C1D57976E0@DB5PR0401MB1845.eurprd04.prod.outlook.com>
Date:	Thu, 21 Apr 2016 15:47:56 +0000
From:	Han Xu <han.xu@....com>
To:	Yunhui Cui <yunhui.cui@....com>, Yunhui Cui <B56489@...escale.com>,
	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	"computersforpeace@...il.com" <computersforpeace@...il.com>,
	"han.xu@...escale.com" <han.xu@...escale.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, Yao Yuan <yao.yuan@....com>
Subject: Re: [PATCH 8/9] mtd: fsl-quadspi: disable AHB buffer prefetch



________________________________________
From: Yunhui Cui
Sent: Thursday, April 21, 2016 3:41 AM
To: Han Xu; Yunhui Cui; dwmw2@...radead.org; computersforpeace@...il.com; han.xu@...escale.com
Cc: linux-kernel@...r.kernel.org; linux-mtd@...ts.infradead.org; linux-arm-kernel@...ts.infradead.org; Yao Yuan
Subject: RE: [PATCH 8/9] mtd: fsl-quadspi: disable AHB buffer prefetch

On Thu, Apr 24, 2016 at 06:37:01 AM +0800, Han Xu wrote:
> ________________________________________
> From: Yunhui Cui <B56489@...escale.com>
> Sent: Wednesday, April 13, 2016 9:50 PM
> To: dwmw2@...radead.org; computersforpeace@...il.com;
> han.xu@...escale.com
> Cc: linux-kernel@...r.kernel.org; linux-mtd@...ts.infradead.org; linux-
> arm-kernel@...ts.infradead.org; Yao Yuan; Yunhui Cui
> Subject: [PATCH 8/9] mtd: fsl-quadspi: disable AHB buffer prefetch
>
> From: Yunhui Cui <yunhui.cui@....com>
>
> A-009282: QuadSPI: QuadSPI data pre-fetch can result in incorrect data
> Affects: QuadSPI
> Description: With AHB buffer prefetch enabled, the QuadSPI may return
> incorrect data on the AHB interface. The buffer pre-fetch is enabled if
> the fetch size as configured either in the LUT or in the BUFxCR register
> is greater than 8 bytes.
> Impact: Only 64 bit read allowed.
> Workaround: Keep the read data size to 64 bits (8 Bytes), which disables
> the prefetch on the AHB buffer, and prevents this issue from occurring.
>
> Signed-off-by: Yunhui Cui <yunhui.cui@....com>
> ---
>  drivers/mtd/spi-nor/fsl-quadspi.c | 29 +++++++++++++++++++++++------
>  1 file changed, 23 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mtd/spi-nor/fsl-quadspi.c b/drivers/mtd/spi-nor/fsl-
> quadspi.c
> index fea18b6..d9f3e50 100644
> --- a/drivers/mtd/spi-nor/fsl-quadspi.c
> +++ b/drivers/mtd/spi-nor/fsl-quadspi.c
> @@ -752,19 +752,36 @@ static void fsl_qspi_init_abh_read(struct fsl_qspi
> *q)  {
>         void __iomem *base = q->iobase;
>         int seqid;
> +       const struct fsl_qspi_devtype_data *devtype_data =
> + q->devtype_data;
>
>         /* AHB configuration for access buffer 0/1/2 .*/
>         qspi_writel(q, QUADSPI_BUFXCR_INVALID_MSTRID, base +
> QUADSPI_BUF0CR);
>         qspi_writel(q, QUADSPI_BUFXCR_INVALID_MSTRID, base +
> QUADSPI_BUF1CR);
>         qspi_writel(q, QUADSPI_BUFXCR_INVALID_MSTRID, base +
> QUADSPI_BUF2CR);
> +
>         /*
> -        * Set ADATSZ with the maximum AHB buffer size to improve the
> -        * read performance.
> +        * Errata: A-009282: QuadSPI data prefetch may result in
> incorrect data
> +        * Workaround: Keep the read data size to 64 bits (8 bytes).
> +        * This disables the prefetch on the AHB buffer and
> +        * prevents this issue from occurring.
>          */
> -       qspi_writel(q, QUADSPI_BUF3CR_ALLMST_MASK |
> -                       ((q->devtype_data->ahb_buf_size / 8)
> -                       << QUADSPI_BUF3CR_ADATSZ_SHIFT),
> -                       base + QUADSPI_BUF3CR);
> +       if (devtype_data->devtype == FSL_QUADSPI_LS2080A ||
> +           devtype_data->devtype == FSL_QUADSPI_LS1021A) {
>
> Use QUIRK, not SoC name.
[Yunhui] This is a SoC errata, we need distinguish according to the devtype_data->devtype

It's the same thing and we have already done that before.

/*
 * TKT253890, Controller needs driver to fill txfifo till 16 byte to
 * trigger data transfer even though extra data will not transferred.
 */
#define QUADSPI_QUIRK_TKT253890         (1 << 2)
/* Controller cannot wake up from wait mode, TKT245618 */
#define QUADSPI_QUIRK_TKT245618         (1 << 3)


> +
> +               qspi_writel(q, QUADSPI_BUF3CR_ALLMST_MASK |
> +                               (1 << QUADSPI_BUF3CR_ADATSZ_SHIFT),
> +                               base + QUADSPI_BUF3CR);
> +
> +       } else {
> +               /*
> +                * Set ADATSZ with the maximum AHB buffer size to improve
> the
> +                * read performance.
> +               */
> +               qspi_writel(q, QUADSPI_BUF3CR_ALLMST_MASK |
> +                               ((q->devtype_data->ahb_buf_size / 8)
> +                               << QUADSPI_BUF3CR_ADATSZ_SHIFT),
> +                               base + QUADSPI_BUF3CR);
> +       }
>
>         /* We only use the buffer3 */
>         qspi_writel(q, 0, base + QUADSPI_BUF0IND);
> --
> 2.1.0.27.g96db324