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From: Loc Ho <lho@apm.com>
Date: Fri, 28 Oct 2016 10:07:26 -0700
Message-ID: <CAPw-ZT=XYA3Q=nYC649iC41eebC8fqMsiOaG+O8mhP24D4JN5Q@mail.gmail.com>
Subject: Re: [PATCHv2] clk: xgene: Don't call __pa on ioremaped address
To: Laura Abbott <labbott@redhat.com>
Cc: Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@codeaurora.org>, linux-clk@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Hi Laura,

> ioremaped addresses are not linearly mapped so the physical
> address can not be figured out via __pa. More generally, there
> is no guarantee that backing value of an ioremapped address
> is a physical address at all. The value here is only used
> for debugging so just drop the call to __pa on the ioremapped
> address.
>
> Fixes: 6ae5fd381251 ("clk: xgene: Silence sparse warnings")
> Signed-off-by: Laura Abbott <labbott@redhat.com>
> ---
> v2: Fix up one more format string
>
> I put the fixes tag to match with the cleanup that was done.
> If there is interest in this fix for pre-4.2 kernels for
> stable, I can submit a patch for that as well.
> ---
>  drivers/clk/clk-xgene.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/clk/clk-xgene.c b/drivers/clk/clk-xgene.c
> index 3433132..1e67655 100644
> --- a/drivers/clk/clk-xgene.c
> +++ b/drivers/clk/clk-xgene.c
> @@ -243,22 +243,20 @@ static int xgene_clk_enable(struct clk_hw *hw)
>         struct xgene_clk *pclk = to_xgene_clk(hw);
>         unsigned long flags = 0;
>         u32 data;
> -       phys_addr_t reg;
>
>         if (pclk->lock)
>                 spin_lock_irqsave(pclk->lock, flags);
>
>         if (pclk->param.csr_reg != NULL) {
>                 pr_debug("%s clock enabled\n", clk_hw_get_name(hw));
> -               reg = __pa(pclk->param.csr_reg);
>                 /* First enable the clock */
>                 data = xgene_clk_read(pclk->param.csr_reg +
>                                         pclk->param.reg_clk_offset);
>                 data |= pclk->param.reg_clk_mask;
>                 xgene_clk_write(data, pclk->param.csr_reg +
>                                         pclk->param.reg_clk_offset);
> -               pr_debug("%s clock PADDR base %pa clk offset 0x%08X mask 0x%08X value 0x%08X\n",
> -                       clk_hw_get_name(hw), &reg,
> +               pr_debug("%s clk offset 0x%08X mask 0x%08X value 0x%08X\n",
> +                       clk_hw_get_name(hw),
>                         pclk->param.reg_clk_offset, pclk->param.reg_clk_mask,
>                         data);
>
> @@ -268,8 +266,8 @@ static int xgene_clk_enable(struct clk_hw *hw)
>                 data &= ~pclk->param.reg_csr_mask;
>                 xgene_clk_write(data, pclk->param.csr_reg +
>                                         pclk->param.reg_csr_offset);
> -               pr_debug("%s CSR RESET PADDR base %pa csr offset 0x%08X mask 0x%08X value 0x%08X\n",
> -                       clk_hw_get_name(hw), &reg,
> +               pr_debug("%s csr offset 0x%08X mask 0x%08X value 0x%08X\n",
> +                       clk_hw_get_name(hw),
>                         pclk->param.reg_csr_offset, pclk->param.reg_csr_mask,
>                         data);
>         }


The code looks fine to me. May be overly cautious here. Do you have a
board to test this out?

-Loc