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

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Message-ID: <61f3cc1e-66f4-86d7-659b-9ff1219b4274@broadcom.com>
Date: Fri, 19 Jan 2024 10:04:46 -0800
From: William Zhang <william.zhang@...adcom.com>
To: Dan Carpenter <dan.carpenter@...aro.org>, 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,
 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

Hi,

On 01/18/2024 09:36 PM, Dan Carpenter wrote:
> 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().
> 
Yes that's a typo. Fallback to memcpy_fromio when unalgined.  Will 
update the comments in v3. Thanks!

> regards,
> dan carpenter
> 

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