From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Bastien Curutchet <bastien.curutchet@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 12:17:17 +0100 [thread overview]
Message-ID: <87y11osnuq.fsf@bootlin.com> (raw)
In-Reply-To: <07cd5d53-ce99-4ada-a7f1-53795eff5c42@bootlin.com> (Bastien Curutchet's message of "Tue, 12 Nov 2024 10:13:38 +0100")
Hi Bastien,
On 12/11/2024 at 10:13:38 +01, Bastien Curutchet <bastien.curutchet@bootlin.com> wrote:
> 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.
Okay, and I guess we can have more than one children, in this case
indeed we need serialization.
>> 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.
In general, I believe in a path that is not a hot-path and if you can
sleep, you should go for a mutex.
Cheers,
Miquèl
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next prev parent reply other threads:[~2024-11-12 11:50 UTC|newest]
Thread overview: 13+ 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 ` [PATCH v2 1/6] memory: ti-aemif: Create aemif_set_cs_timings() Bastien Curutchet
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
2024-11-11 19:21 ` Miquel Raynal
2024-11-12 9:13 ` Bastien Curutchet
2024-11-12 11:17 ` Miquel Raynal [this message]
2024-11-06 8:55 ` [PATCH v2 3/6] mtd: rawnand: davinci: Always depends on TI_AEMIF Bastien Curutchet
2024-11-06 8:55 ` [PATCH v2 4/6] mtd: rawnand: davinci: Order headers alphabetically Bastien Curutchet
2024-11-06 8:55 ` [PATCH v2 5/6] mtd: rawnand: davinci: Add clock resource Bastien Curutchet
2024-11-06 8:55 ` [PATCH v2 6/6] mtd: rawnand: davinci: Implement setup_interface() operation Bastien Curutchet
2024-11-11 19:32 ` Miquel Raynal
2024-11-12 12:53 ` Bastien Curutchet
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