linux-kernel - Re: [PATCH v2 05/10] mtd: rawnand: brcmnand: Add BCMBCA read data bus interface

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Message-ID: <4b3f4316-0da4-4fde-a806-7b579948db50@moroto.mountain>
Date: Fri, 19 Jan 2024 08:36:21 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: dregan@...adcom.com
Cc: dregan@...l.com, miquel.raynal@...tlin.com, richard@....at,
	vigneshr@...com, robh+dt@...nel.org,
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
	computersforpeace@...il.com, kdasu.kdev@...il.com,
	linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, joel.peshkin@...adcom.com,
	tomer.yacoby@...adcom.com, dan.beygelman@...adcom.com,
	william.zhang@...adcom.com, anand.gore@...adcom.com,
	kursad.oney@...adcom.com, florian.fainelli@...adcom.com,
	rafal@...ecki.pl, bcm-kernel-feedback-list@...adcom.com,
	andre.przywara@....com, baruch@...s.co.il,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 05/10] mtd: rawnand: brcmnand: Add BCMBCA read data
 bus interface

On Thu, Jan 18, 2024 at 11:53:51AM -0800, dregan@...adcom.com wrote:
> diff --git a/drivers/mtd/nand/raw/brcmnand/bcmbca_nand.c b/drivers/mtd/nand/raw/brcmnand/bcmbca_nand.c
> index 3e2f3b79788d..e97e13ae246c 100644
> --- a/drivers/mtd/nand/raw/brcmnand/bcmbca_nand.c
> +++ b/drivers/mtd/nand/raw/brcmnand/bcmbca_nand.c
> @@ -26,6 +26,18 @@ enum {
>  	BCMBCA_CTLRDY		= BIT(4),
>  };
>  
> +#if defined(CONFIG_ARM64)
> +#define ALIGN_REQ		8
> +#else
> +#define ALIGN_REQ		4
> +#endif
> +
> +static inline bool bcmbca_nand_is_buf_aligned(void *flash_cache,  void *buffer)
> +{
> +	return IS_ALIGNED((uintptr_t)buffer, ALIGN_REQ) &&
> +				IS_ALIGNED((uintptr_t)flash_cache, ALIGN_REQ);
> +}
> +
>  static bool bcmbca_nand_intc_ack(struct brcmnand_soc *soc)
>  {
>  	struct bcmbca_nand_soc *priv =
> @@ -56,6 +68,20 @@ static void bcmbca_nand_intc_set(struct brcmnand_soc *soc, bool en)
>  	brcmnand_writel(val, mmio);
>  }
>  
> +static void bcmbca_read_data_bus(struct brcmnand_soc *soc,
> +				 void __iomem *flash_cache,  u32 *buffer, int fc_words)
> +{
> +	/*
> +	 * memcpy can do unaligned aligned access depending on source
> +	 * and dest address, which is incompatible with nand cache. Fallback
> +	 * to the memcpy for io version
> +	 */
> +	if (bcmbca_nand_is_buf_aligned((void *)flash_cache, buffer))
> +		memcpy((void *)buffer, (void *)flash_cache, fc_words * 4);
> +	else
> +		memcpy_fromio((void *)buffer, flash_cache, fc_words * 4);
> +}

This comment is confusing or maybe the if statement is reversed...
We're falling back to memcpy_fromio() for the unaligned accesses but the
comment says we're falling back to memcpy().

regards,
dan carpenter