linux-kernel - Re: [PATCH] scsi: ufs: core: Limit DMA alignment check

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Message-ID: <20230201175943.GB14334@asutoshd-linux1.qualcomm.com>
Date:   Wed, 1 Feb 2023 09:59:43 -0800
From:   Asutosh Das <quic_asutoshd@...cinc.com>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>
CC:     Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        Bart Van Assche <bvanassche@....org>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "Bean Huo" <beanhuo@...ron.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        "Jinyoung Choi" <j-young.choi@...sung.com>,
        <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <mani@...nel.org>
Subject: Re: [PATCH] scsi: ufs: core: Limit DMA alignment check

On Tue, Jan 31 2023 at 19:49 -0800, Bjorn Andersson wrote:
>The three DMA memory regions allocated for the host memory space is
>documented to require alignment of 128, 1024 and 1024 respectively, but
>the returned address is checked for PAGE_SIZE alignment.
>
>In the case these allocations are serviced by e.g. the Arm SMMU, the
>size and alignment will be determined by its supported page sizes. In
>most cases SZ_4K and a few larger sizes are available.
>
>In the typical configuration this does not cause problems, but in the
>event that the system PAGE_SIZE is increased beyond 4k, it's no longer
>reasonable to expect that the allocation will be PAGE_SIZE aligned.
>
>Limit the DMA alignment check to the actual alignment requirements
>written in the comments in the code, to avoid the UFS core refusing to
>initialize with such configuration.
>
>Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>

Reviewed-by: Asutosh Das <quic_asutoshd@...cinc.com>

>---
> drivers/ufs/core/ufshcd.c | 9 +++------
> 1 file changed, 3 insertions(+), 6 deletions(-)
>
>diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
>index ec732e4bbbf4..d7f3f1ba9d12 100644
>--- a/drivers/ufs/core/ufshcd.c
>+++ b/drivers/ufs/core/ufshcd.c
>@@ -3724,12 +3724,9 @@ static int ufshcd_memory_alloc(struct ufs_hba *hba)
>
> 	/*
> 	 * UFSHCI requires UTP command descriptor to be 128 byte aligned.
>-	 * make sure hba->ucdl_dma_addr is aligned to PAGE_SIZE
>-	 * if hba->ucdl_dma_addr is aligned to PAGE_SIZE, then it will
>-	 * be aligned to 128 bytes as well
> 	 */
> 	if (!hba->ucdl_base_addr ||
>-	    WARN_ON(hba->ucdl_dma_addr & (PAGE_SIZE - 1))) {
>+	    WARN_ON(hba->ucdl_dma_addr & (128 - 1))) {
> 		dev_err(hba->dev,
> 			"Command Descriptor Memory allocation failed\n");
> 		goto out;
>@@ -3745,7 +3742,7 @@ static int ufshcd_memory_alloc(struct ufs_hba *hba)
> 						   &hba->utrdl_dma_addr,
> 						   GFP_KERNEL);
> 	if (!hba->utrdl_base_addr ||
>-	    WARN_ON(hba->utrdl_dma_addr & (PAGE_SIZE - 1))) {
>+	    WARN_ON(hba->utrdl_dma_addr & (1024 - 1))) {
> 		dev_err(hba->dev,
> 			"Transfer Descriptor Memory allocation failed\n");
> 		goto out;
>@@ -3769,7 +3766,7 @@ static int ufshcd_memory_alloc(struct ufs_hba *hba)
> 						    &hba->utmrdl_dma_addr,
> 						    GFP_KERNEL);
> 	if (!hba->utmrdl_base_addr ||
>-	    WARN_ON(hba->utmrdl_dma_addr & (PAGE_SIZE - 1))) {
>+	    WARN_ON(hba->utmrdl_dma_addr & (1024 - 1))) {
> 		dev_err(hba->dev,
> 		"Task Management Descriptor Memory allocation failed\n");
> 		goto out;
>-- 
>2.25.1
>