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From: Bastien Curutchet <bastien.curutchet@bootlin.com>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Santosh Shilimkar <ssantosh@kernel.org>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Herve Codina <herve.codina@bootlin.com>,
	Christopher Cordahi <christophercordahi@nanometrics.ca>
Subject: Re: [PATCH v2 2/6] memory: ti-aemif: Export aemif_set_cs_timings()
Date: Tue, 12 Nov 2024 10:13:38 +0100	[thread overview]
Message-ID: <07cd5d53-ce99-4ada-a7f1-53795eff5c42@bootlin.com> (raw)
In-Reply-To: <87ttcdr2ym.fsf@bootlin.com>

Hi Miquèl,

On 11/11/24 8:21 PM, Miquel Raynal wrote:
> 
> Hello Bastien,
> 
> On 06/11/2024 at 09:55:03 +01, Bastien Curutchet <bastien.curutchet@bootlin.com> wrote:
> 
>> Export the aemif_set_cs_timing() symbol so it can be used by other
>> drivers
>>
>> Add a spinlock to protect the CS configuration register from concurrent
>> accesses.
> 
> What concurrent accesses are you trying to protect yourself against?
> I fail to see the use case, but TBH I haven't tried hard enough maybe.
> 

The register that handles the CS configuration belongs to the AEMIF 
component but it will also be accessed by the AEMIF 'children' with the 
aemif_set_cs_timing() function. So far, concurrent accesses shouldn't 
occur because the AEMIF configures the CS timings only once and does so 
before probing its 'children'; but I don't know how things can evolve in 
the future.

> Also, what justifies the use of a spin-lock in this case?
> 

TBH, I always struggle to choose between mutexes and spin-locks. I chose 
spin-lock because it only protects one memory-mapped register so I think 
it doesn't worth going to sleep when waiting for the lock.


Best regards,
Bastien

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

WARNING: multiple messages have this Message-ID (diff)
From: Bastien Curutchet <bastien.curutchet@bootlin.com>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Santosh Shilimkar <ssantosh@kernel.org>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Herve Codina <herve.codina@bootlin.com>,
	Christopher Cordahi <christophercordahi@nanometrics.ca>
Subject: Re: [PATCH v2 2/6] memory: ti-aemif: Export aemif_set_cs_timings()
Date: Tue, 12 Nov 2024 10:13:38 +0100	[thread overview]
Message-ID: <07cd5d53-ce99-4ada-a7f1-53795eff5c42@bootlin.com> (raw)
In-Reply-To: <87ttcdr2ym.fsf@bootlin.com>

Hi Miquèl,

On 11/11/24 8:21 PM, Miquel Raynal wrote:
> 
> Hello Bastien,
> 
> On 06/11/2024 at 09:55:03 +01, Bastien Curutchet <bastien.curutchet@bootlin.com> wrote:
> 
>> Export the aemif_set_cs_timing() symbol so it can be used by other
>> drivers
>>
>> Add a spinlock to protect the CS configuration register from concurrent
>> accesses.
> 
> What concurrent accesses are you trying to protect yourself against?
> I fail to see the use case, but TBH I haven't tried hard enough maybe.
> 

The register that handles the CS configuration belongs to the AEMIF 
component but it will also be accessed by the AEMIF 'children' with the 
aemif_set_cs_timing() function. So far, concurrent accesses shouldn't 
occur because the AEMIF configures the CS timings only once and does so 
before probing its 'children'; but I don't know how things can evolve in 
the future.

> Also, what justifies the use of a spin-lock in this case?
> 

TBH, I always struggle to choose between mutexes and spin-locks. I chose 
spin-lock because it only protects one memory-mapped register so I think 
it doesn't worth going to sleep when waiting for the lock.


Best regards,
Bastien

  reply	other threads:[~2024-11-12  9:13 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-11-06  8:55 [PATCH v2 0/6] Implement setup_interface() in the DaVinci NAND controller Bastien Curutchet
2024-11-06  8:55 ` Bastien Curutchet
2024-11-06  8:55 ` [PATCH v2 1/6] memory: ti-aemif: Create aemif_set_cs_timings() Bastien Curutchet
2024-11-06  8:55   ` Bastien Curutchet
2024-11-11 19:16   ` Miquel Raynal
2024-11-11 19:16     ` Miquel Raynal
2024-11-06  8:55 ` [PATCH v2 2/6] memory: ti-aemif: Export aemif_set_cs_timings() Bastien Curutchet
2024-11-06  8:55   ` Bastien Curutchet
2024-11-11 19:21   ` Miquel Raynal
2024-11-11 19:21     ` Miquel Raynal
2024-11-12  9:13     ` Bastien Curutchet [this message]
2024-11-12  9:13       ` Bastien Curutchet
2024-11-12 11:17       ` Miquel Raynal
2024-11-12 11:17         ` Miquel Raynal
2024-11-06  8:55 ` [PATCH v2 3/6] mtd: rawnand: davinci: Always depends on TI_AEMIF Bastien Curutchet
2024-11-06  8:55   ` Bastien Curutchet
2024-11-06  8:55 ` [PATCH v2 4/6] mtd: rawnand: davinci: Order headers alphabetically Bastien Curutchet
2024-11-06  8:55   ` Bastien Curutchet
2024-11-06  8:55 ` [PATCH v2 5/6] mtd: rawnand: davinci: Add clock resource Bastien Curutchet
2024-11-06  8:55   ` Bastien Curutchet
2024-11-06  8:55 ` [PATCH v2 6/6] mtd: rawnand: davinci: Implement setup_interface() operation Bastien Curutchet
2024-11-06  8:55   ` Bastien Curutchet
2024-11-11 19:32   ` Miquel Raynal
2024-11-11 19:32     ` Miquel Raynal
2024-11-12 12:53     ` Bastien Curutchet
2024-11-12 12:53       ` Bastien Curutchet

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