[PATCH] fsi: aspeed: Emit fewer barriers in opb operations
Eddie James
eajames at linux.ibm.com
Wed Apr 14 06:08:52 AEST 2021
On Tue, 2021-02-23 at 14:47 +1030, Joel Stanley wrote:
> When setting up a read or write to the OPB memory space, we must
> perform
> five or six AHB writes. The ordering of these up until the trigger
> write
> does not matter, so use writel_relaxed.
Reviewed-by: Eddie James <eajames at linux.ibm.com>
I have also tested this patch on hardware, so
Tested-by: Eddie James <eajames at linux.ibm.com>
>
> The generated code goes from (Debian GCC 10.2.1-6):
>
> mov r8, r3
> mcr 15, 0, sl, cr7, cr10, {4}
> str sl, [r6, #20]
> mcr 15, 0, sl, cr7, cr10, {4}
> str r3, [r6, #24]
> mcr 15, 0, sl, cr7, cr10, {4}
> str r1, [r6, #28]
> mcr 15, 0, sl, cr7, cr10, {4}
> str r2, [r6, #32]
> mcr 15, 0, sl, cr7, cr10, {4}
> mov r1, #1
> str r1, [r6, #64] ; 0x40
> mcr 15, 0, sl, cr7, cr10, {4}
> str r1, [r6, #4]
>
> to this:
>
> str r3, [r7, #20]
> str r2, [r7, #24]
> str r1, [r7, #28]
> str r3, [r7, #64]
> mov r8, #0
> mcr 15, 0, r8, cr7, cr10, {4}
> str r3, [r7, #4]
>
> Signed-off-by: Joel Stanley <joel at jms.id.au>
> ---
> drivers/fsi/fsi-master-aspeed.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/fsi/fsi-master-aspeed.c b/drivers/fsi/fsi-
> master-aspeed.c
> index 90dbe58ca1ed..09fff86b2bac 100644
> --- a/drivers/fsi/fsi-master-aspeed.c
> +++ b/drivers/fsi/fsi-master-aspeed.c
> @@ -101,11 +101,11 @@ static int __opb_write(struct fsi_master_aspeed
> *aspeed, u32 addr,
> u32 reg, status;
> int ret;
>
> - writel(CMD_WRITE, base + OPB0_RW);
> - writel(transfer_size, base + OPB0_XFER_SIZE);
> - writel(addr, base + OPB0_FSI_ADDR);
> - writel(val, base + OPB0_FSI_DATA_W);
> - writel(0x1, base + OPB_IRQ_CLEAR);
> + writel_relaxed(CMD_WRITE, base + OPB0_RW);
> + writel_relaxed(transfer_size, base + OPB0_XFER_SIZE);
> + writel_relaxed(addr, base + OPB0_FSI_ADDR);
> + writel_relaxed(val, base + OPB0_FSI_DATA_W);
> + writel_relaxed(0x1, base + OPB_IRQ_CLEAR);
> writel(0x1, base + OPB_TRIGGER);
>
> ret = readl_poll_timeout(base + OPB_IRQ_STATUS, reg,
> @@ -149,10 +149,10 @@ static int __opb_read(struct fsi_master_aspeed
> *aspeed, uint32_t addr,
> u32 result, reg;
> int status, ret;
>
> - writel(CMD_READ, base + OPB0_RW);
> - writel(transfer_size, base + OPB0_XFER_SIZE);
> - writel(addr, base + OPB0_FSI_ADDR);
> - writel(0x1, base + OPB_IRQ_CLEAR);
> + writel_relaxed(CMD_READ, base + OPB0_RW);
> + writel_relaxed(transfer_size, base + OPB0_XFER_SIZE);
> + writel_relaxed(addr, base + OPB0_FSI_ADDR);
> + writel_relaxed(0x1, base + OPB_IRQ_CLEAR);
> writel(0x1, base + OPB_TRIGGER);
>
> ret = readl_poll_timeout(base + OPB_IRQ_STATUS, reg,
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