linux-kernel - Re: [PATCH V6 5/9] mmc: sdhci: Add 32-bit block count support for v4 mode

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Date:   Mon, 27 Aug 2018 10:07:37 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Chunyan Zhang <zhang.chunyan@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang@...aro.org>,
        Billows Wu <billows.wu@...soc.com>,
        Jason Wu <jason.wu@...soc.com>,
        Chunyan Zhang <chunyan.zhang@...soc.com>,
        Chunyan Zhang <zhang.lyra@...il.com>
Subject: Re: [PATCH V6 5/9] mmc: sdhci: Add 32-bit block count support for v4
 mode

On 24/08/18 12:20, Chunyan Zhang wrote:
> Host Controller Version 4.10 re-defines SDMA System Address register
> as 32-bit Block Count for v4 mode, and SDMA uses ADMA System
> Address register (05Fh-058h) instead if v4 mode is enabled. Also
> when using 32-bit block count, 16-bit block count register need
> to be set to zero.
> 
> Since using 32-bit Block Count would cause problems for auto-cmd23,
> it can be chosen via host->quirk2.
> 
> Signed-off-by: Chunyan Zhang <zhang.chunyan@...aro.org>
> ---
>  drivers/mmc/host/sdhci.c | 15 ++++++++++++++-
>  drivers/mmc/host/sdhci.h |  3 +++
>  2 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 38d083c..05f9fff 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1073,7 +1073,20 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_command *cmd)
>  	/* Set the DMA boundary value and block size */
>  	sdhci_writew(host, SDHCI_MAKE_BLKSZ(host->sdma_boundary, data->blksz),
>  		     SDHCI_BLOCK_SIZE);
> -	sdhci_writew(host, data->blocks, SDHCI_BLOCK_COUNT);
> +
> +	/*
> +	 * For Version 4.10 onwards, if v4 mode is enabled, 16-bit Block Count
> +	 * register need to be set to zero, 32-bit Block Count register would
> +	 * be selected.
> +	 */
> +	if (host->version >= SDHCI_SPEC_410 && host->v4_mode &&
> +	    !(host->quirks2 & SDHCI_QUIRK2_BROKEN_32BIT_BLK_CNT)) {

Because 32-bit block count is problematic but also not essential, I would
prefer to do the quirk the other way around. i.e. SDHCI_QUIRK2_USE_32BIT_BLK_CNT

I would also add a comment to the definition of
SDHCI_QUIRK2_USE_32BIT_BLK_CNT, like:

32-bit block count may not support eMMC where upper bits of CMD23 are used
for other purposes.  Consequently we support 16-bit block count by default.
Otherwise, SDHCI_QUIRK2_USE_32BIT_BLK_CNT can be selected to use 32-bit
block count.

> +		if (sdhci_readw(host, SDHCI_BLOCK_COUNT))
> +			sdhci_writew(host, 0, SDHCI_BLOCK_COUNT);
> +		sdhci_writew(host, data->blocks, SDHCI_32BIT_BLK_CNT);
> +	} else {
> +		sdhci_writew(host, data->blocks, SDHCI_BLOCK_COUNT);
> +	}
>  }
>  
>  static inline bool sdhci_auto_cmd12(struct sdhci_host *host,
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index f3b9ebc..0a1e25f 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -28,6 +28,7 @@
>  
>  #define SDHCI_DMA_ADDRESS	0x00
>  #define SDHCI_ARGUMENT2		SDHCI_DMA_ADDRESS
> +#define SDHCI_32BIT_BLK_CNT	SDHCI_DMA_ADDRESS
>  
>  #define SDHCI_BLOCK_SIZE	0x04
>  #define  SDHCI_MAKE_BLKSZ(dma, blksz) (((dma & 0x7) << 12) | (blksz & 0xFFF))
> @@ -462,6 +463,8 @@ struct sdhci_host {
>   * obtainable timeout.
>   */
>  #define SDHCI_QUIRK2_DISABLE_HW_TIMEOUT			(1<<17)
> +/* Controller broken with using 32-bit block count in v4_mode */
> +#define SDHCI_QUIRK2_BROKEN_32BIT_BLK_CNT		(1<<18)
>  
>  	int irq;		/* Device IRQ */
>  	void __iomem *ioaddr;	/* Mapped address */
>