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Thu, 22 Aug 2024 15:50:05 -0700 (PDT) Received: from [10.67.48.245] ([192.19.223.252]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-203855664e2sm17414465ad.30.2024.08.22.15.50.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Aug 2024 15:50:04 -0700 (PDT) Message-ID: <078bc5ee-e591-427b-a9fe-9386738a847f@broadcom.com> Date: Thu, 22 Aug 2024 15:50:03 -0700 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/2] firmware: arm_scmi: Support 'reg-io-width' property for shared memory To: Sudeep Holla Cc: linux-arm-kernel@lists.infradead.org, Rob Herring , Krzysztof Kozlowski , Conor Dooley , Cristian Marussi , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , open list , "open list:SYSTEM CONTROL & POWER/MANAGEMENT INTERFACE" , justin.chen@broadcom.com, opendmb@gmail.com, kapil.hali@broadcom.com, bcm-kernel-feedback-list@broadcom.com References: <20240816224221.3256455-1-florian.fainelli@broadcom.com> <20240816224221.3256455-3-florian.fainelli@broadcom.com> Content-Language: en-US From: Florian Fainelli Autocrypt: addr=florian.fainelli@broadcom.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/22/24 03:46, Sudeep Holla wrote: > Hi Florian, > > Sorry for getting late to this party, I wasn't able to review this before. > Overall changes look correct. But my main concern is that is SCMI the right > place to have such IO accessors. It is better to run it through Arnd if > he is happy with it before I send him the pull request containing these. Sure, would definitively want more eyes to review. > > On Fri, Aug 16, 2024 at 03:42:21PM -0700, Florian Fainelli wrote: >> Some shared memory areas might only support a certain access width, >> such as 32-bit, which memcpy_{from,to}_io() does not adhere to at least >> on ARM64 by making both 8-bit and 64-bit accesses to such memory. >> > > Is this limitation on the hardware for both read and writes ? This applies to both reads and writes. We have to make accesses on a 4 byte boundary and of exactly 4 bytes in size. > The reason I ask is I see arm64 does have memcpy_toio_aligned() or > __iowrite32_copy_full() for 32 bit aligned writes. > That appears to work nicely on ARM64 and ARM 32-bit, thanks for the suggestion! One needs to be careful that __io{read,write}32_copy takes 32-bit units, not bytes! FWIW, here is my diff between v3 and v4: diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h index 73bb496fac01..a13f79b37c99 100644 --- a/drivers/firmware/arm_scmi/common.h +++ b/drivers/firmware/arm_scmi/common.h @@ -319,9 +319,9 @@ enum scmi_bad_msg { /* Used for compactness and signature validation of the function pointers being * passed. */ -typedef void (*shmem_copy_toio_t)(volatile void __iomem *to, const void *from, +typedef void (*shmem_copy_toio_t)(void __iomem *to, const void *from, size_t count); -typedef void (*shmem_copy_fromio_t)(void *to, const volatile void __iomem *from, +typedef void (*shmem_copy_fromio_t)(void *to, const void __iomem *from, size_t count); /** diff --git a/drivers/firmware/arm_scmi/shmem.c b/drivers/firmware/arm_scmi/shmem.c index aded5f1cd49f..e9f30ab671a8 100644 --- a/drivers/firmware/arm_scmi/shmem.c +++ b/drivers/firmware/arm_scmi/shmem.c @@ -35,33 +35,25 @@ struct scmi_shared_mem { }; static inline void shmem_memcpy_fromio32(void *to, - const volatile void __iomem *from, + const void __iomem *from, size_t count) { - while (count) { - *(u32 *)to = __raw_readl(from); - from += 4; - to += 4; - count -= 4; - } + WARN_ON(!IS_ALIGNED((unsigned long)from, 4) || + !IS_ALIGNED((unsigned long)to, 4) || + count % 4); - /* Ensure all reads from I/O have completed */ - rmb(); + __ioread32_copy(to, from, count / 4); } -static inline void shmem_memcpy_toio32(volatile void __iomem *to, +static inline void shmem_memcpy_toio32(void __iomem *to, const void *from, size_t count) { - while (count) { - __raw_writel(*(u32 *)from, to); - from += 4; - to += 4; - count -= 4; - } + WARN_ON(!IS_ALIGNED((unsigned long)to, 4) || + !IS_ALIGNED((unsigned long)from, 4) || + count % 4); - /* Ensure all writes to I/O have completed */ - wmb(); + __iowrite32_copy(to, from, count / 4); } static struct scmi_shmem_io_ops shmem_io_ops32 = { @@ -73,13 +65,13 @@ static struct scmi_shmem_io_ops shmem_io_ops32 = { * pre-processor. */ static inline void shmem_memcpy_fromio(void *to, - const volatile void __iomem *from, + const void __iomem *from, size_t count) { memcpy_fromio(to, from, count); } -static inline void shmem_memcpy_toio(volatile void __iomem *to, +static inline void shmem_memcpy_toio(void __iomem *to, const void *from, size_t count) { -- Florian